CHAPTER 3
The Botany of Citrus and Its Wild Relatives
BY WALTER T. SWINGLE
Revised by Phillip C. Reece
This account
of the citrus fruits and their numerous wild relatives has been written
in the hope of interesting both citrus growers and expert citrus
investigators in this large array of plants. Nearly every
one of them has some striking character—beauty of foliage; fragrance and
beauty of the flowers; bright color of the fruits; or, more
practically, probable value as a rootstock for some of the commonly
cultivated species of Citrus or even possible use in breeding new types of citrus fruits by hybridization.
The vast majority of citrus fruits and
their wild relatives are native to southeastern Asia, the East Indian
Archipelago, New Guinea, Melanesia, New Caledonia, and Australia;
another group occurs in tropical Africa. Many of the most
interesting relatives of Citrus have been collected only once or
twice, and frequently flowers or fruits are still imperfectly
represented even in the largest botanical museums of Europe and
America. Consequently, it has been impossible to have any
consistent or uniform schedule for describing these plants in the
present chapter, but each genus has been given the best treatment that
the material available for study would permit. As a result,
there is presented a connected account of the whole orange subfamily and
of the two tribes into which it is divided, with some remarks on the
geographical distribution and probable evolutionary history of some of
the more important genera of each of these tribes. The
thirty-three genera here discussed, however, have been treated in as
many essays varying somewhat in method, content, and taxonomic technique
with each genus.
Curiously enough, the reader will find
that the best-known material is often described with the fewest words,
whereas in an imperfectly known genus, in which the species are still so
inadequately known as to be difficult to separate without abundant
material, it has seemed necessary to describe each species in minute
detail to make sure that no possible differential character has been
omitted. It is hoped and believed that the reader will find
something of interest in the discussions given under each of the
thirty-three genera.
Each tribe and every genus in the
subfamily is keyed out fully so that any of them can be easily
identified if material is available. Fourteen of the
thirty-three genera contain only a single species, so that the key to
these genera in effect identifies these species. The
remaining nineteen genera, containing from two to many species, are
supplied with keys to determine all the species except with respect to
the genus Glycosmis, where only part of the species are keyed
out, although all are listed. It is much easier to get an
idea of the character of the species by studying the keys than by
reading the detailed descriptions, which are to be considered as
material for reference. These technical descriptions may,
however, at any time become useful in the event any little-known species
becomes important either for ornament or for use in practical citrus
culture.
The commonly cultivated citrus fruits belong to three genera, Citrus, Fortunella, and Poncirus,
all closely related and all belonging to the subtribe Citrinae, of the
tribe Citreae, of the orange subfamily Aurantioideae, of the plant
family Rutaceae. There are six other subfamilies in the
Rutaceae.
The family Rutaceae, in turn, is
obviously related to two other plant families: the Simarubaceae, to
which belongs the tree of heaven, Ailanthus altissima (Mill.) Swing.; and the Meliaceae, of which the Chinaberry, Melia azedarach
L., is a well-known example. These plant families are
classed by taxonomic botanists along with some eighteen other families
in the natural order Geraniales, of which twelve families are included
in the suborder Geraniineae, which includes the Rutaceae.
Although the classification system of
Engler is followed in the arrangement of specimens in the larger
herbaria in this country, it is not phylogenetic in the modem
sense. It follows a logical sequence of steps in the
arrangement of its larger taxa from the simple to the complex on the
premise that evolutionary lines progressed from apetaly to polypetaly
and gamopetaly, apocarpy to syncarpy, hypogyny to epigyny, and
actinomorphy to zygomorphy. Engler believed that flowers
that appear simple have always been simple. This view is now
rejected by most botanists.
Hutchinson (1926) developed a presumed
phylogenetic system of classification based upon many of the principles
on evolutionary trends in the angiosperms adopted earlier by Bessey
(1915) and subscribed to by Fuller and Tippo (1949) and most students of
floral anatomy. The major point of divergence of the
Hutchinson system from earlier systems is the division of the
dicotyledonous plants into two subgroups: the Herbaceae composed of
families that are predominantly herbaceous, and the Lignosae whose
members are predominantly arborescent. Upon this premise the
Rutaceae is placed in the Rutales, an order Hutchinson considers
derived from the Celastrales. This system of classification
places the Rutaceae in a position quite remote from the Geraniales
through which Engler and Diels consider them derived.
Hutchinson's insistence that seed plants
had a monophyletic origin from hypothetical proangiosperms and that
families of predominantly herbaceous plants have evolved from the
Ranales and families of predominantly woody plants from the Magnoliales
has prevented the general acceptance of his system, but it has greatly
stimulated phyletic thinking in recent decades and may ultimately lead
to the development of a system based upon the works of Smith (1938) and
Eames (1936) and an elaboration of the skeletal system of classification
of vascular plants set forth by Tippo (1942).
The orange subfamily includes several
genera with rather numerous species that have a very primitive flower
and fruit structure, much like that of other subfamilies of the Rutaceae
and even analogous to that of several subfamilies in the plant families
Simarubaceae and Miliaceae, which stand very close to the Rutaceae in
the natural system.
First of all, to show at a glance in
clear perspective the proper taxonomic placement of the orange subfamily
in relation to the six other subfamilies of the plant family Rutaceae
to which it belongs, an outline of the Rutaceae is given showing all subfamilies and tribes and subtribes, followed by a concise outline
of the taxonomic arrangement of the orange subfamily listing tribes,
subtribes, subtribal groups, and genera, with page references to each
item.
It is worth noting that before 1943 no
account of the orange subfamily describing all the genera and species of
the world had been published for more than a century. Prior
to publication of the original version of this chapter (Webber and
Batchelor, 1943), the last complete account of the orange subfamily by a
taxonomist was published by Augustin P. de Candolle (1824, vol. 1, pp.
535-40) and contained eleven genera and forty-three species, only a
third as many genera and less than a fourth as many species as are
discussed here.
PRINCIPAL TAXONOMIC WORKS ON CITRUS AND RELATED GENERA PUBLISHED SINCE 1860
In December, 1860, Daniel Oliver read
before the Linnean Society of London a paper entitled "The Natural Order
Aurantiaceae, with a Synopsis of the Indian Species." It
was published the following year (Jour. Linn. Soc. Bot. 5 [2]:
1-44) and covered not only all the genera and species of this order then
known in India (nine genera and thirty-one species), but also fourteen
additional extra-Indian species belonging to six genera, including one
genus not found in India except in cultivation—a grand total of ten
genera and forty-five species. Oliver did not, however,
attempt to treat the genus Citrus. This was the first of the modem high-grade taxonomic works on the orange subfamily.
In 1875, J. D. Hooker recognized thirteen
genera in the orange subfamily with forty-three species (in Citrus he gave only four species) in the account of the family Rutaceae in his Flora of British India (vol. 1).
In 1888, Dr. E. Bonavia brought forth a voluminous treatise, The Cultivated Oranges and Lemons, etc., of India and Ceylon,
with an atlas published in 1890. This highly imaginative
work, by a genuine lover of plants, used for the most part only native
names for the varieties discussed, but it aroused interest all over the
world. Bonavia's theories of the morphology and evolution of
citrus fruits were highly original and ingenious, but departed widely
from the critical standards of professional morphologists and
taxonomists.
In 1910, A. W. Lushington published "The Genus Citrus" (Indian Forester 36:323-53)
and gave names to many of the Indian cultivated varieties studied by
Bonavia. He also named some of the citrus fruit trees
figured and described by Rumphius in the seventeenth century.
Henry N. Ridley, for many years director
of the gardens and forests (including the Singapore Botanic Gardens) in
the former British colony of Straits Settlements, published many
articles on rare Malayan plants, and a five-volume Flora of the Malay Peninsula.
Many new species of the orange subfamily were described by Ridley in
the first series of papers and coordinated with the previously known
ones in his Flora.
W. G. Craib (1926, vol. 1, pp. 215-39), who wrote the Enumeration of the Flora of Siam, discovered and described several very interesting new species of Citrus relatives.
A. Guillaumin, taxonomist of the Musée
d'Histoire Naturelle at Paris, in 1911 gave a detailed illustrated
account of the Rutaceae in Lecomte's Flore genérale de l'Indo-Chine. In the subfamily Aurantioideae he recognized eleven genera and forty-four species, of which six were in Citrus. He also published a valuable paper on the species of Atalantia (in the broad sense) of continental Asia and on the Citrus of New Caledonia (now placed in the genus Oxanthera).
I. H. Burkill, F.L.S., former director of
the Botanic Gardens at Singapore, has taken much interest in the
species of Citrus and related genera that are native in the Malayan region. His "Enumeration of the Species of Paramignya, Atalantia, and Citrus Found in Malay," published in 1931, and his very valuable two-volume work, Dictionary of Economic Products of the Malay Peninsula (1935), were used frequently in preparing this chapter.
E. D. Merrill, former chief of the Bureau
of Science at Manila, P.I., and later administrator of botanical
collections and director of the Arnold Arboretum, Harvard University,
published much valuable information regarding previously published
species and described many new species of Citrus relatives from the Philippines, Borneo, Indo-China, and China.
Tyôzaburô Tanaka, who had specialized,
while a student in the Imperial University, on the study of the
cultivated varieties of Citrus, accompanied the senior author as
guide, interpreter, and assistant through the citrus-growing regions of
Japan in 1915 (and again in 1918 and in 1926). He returned
to Washington with Swingle in 1915 and was employed as his assistant at
different periods from 1915 to 1930 in the former Bureau of Plant
Industry of the U.S. Department of Agriculture.
In 1928-1930, Tanaka made a trip around
the world during which be photographed material of all the genera and
species of the orange subfamily to be found in the principal herbaria of
Europe and America. His studies of this material led to the
publication of a series of papers on the taxonomy of the subfamily
Aurantioideae, entitled "Revisio aurantiacearum." These
papers constitute a very valuable contribution to the taxonomy of this
group. Tanaka's chief works are concerned with satsuma
varieties (Tanaka, 1932c) and citrus species problems (Tanaka, 1954, 1959, and 1961).
In 1896, Dr. Adolph Engler published in the first edition of Die natürlichen Pflanzenfamilien
an account of the plant family Rutaceae. His treatment of
the orange subfamily included fourteen genera, and he estimated the
total number of species at about seventy-one, of which six were in the
genus Citrus. Thirty-five years later Dr. Engler, who
for more than fifty years had specialized on the Rutaceae, wrote, as
his last botanical contribution, a revised account of this family in the
second edition of Die natürlichen Pflanzenfamilien.
He included twenty-nine genera in the Aurantioideae and estimated the
species at about 180, of which eleven were in the genus Citrus.
Between 1912 and 1926, Walter T. Swingle
(the senior author) published seventeen taxonomic papers on tribes,
subtribes, genera, and species of the orange subfamily. Dr.
Engler adopted nine of the genera Swingle proposed and used his
illustrations for several of them. It will be evident to
every reader of this chapter that Swingle has drawn freely on Engler's
great store of knowledge of the orange subfamily.
POSITION OF THE ORANGE SUBFAMILY, AURANTIOIDEAE, IN THE PLANT FAMILY RUTACEAE
The family Rutaceae belongs to the
division Embryophyta Siphonogama, subdivision Angiospermae, class
Dicotyledoneae, subclass Archichlamydeae (Choripetalae and Apetalae),
order Geraniales, suborder 1, Geraniineae, along with eleven other plant
families classed by Engler and Diels (1936, p. xl) in the following
order: Oxalidaceae, Geraniaceae, Tropaeolaceae, Linaceae,
Erythroxylaceae, Zygophyllaceae, Cneoraceae, Rutaceae, Simarubaceae,
Burseraceae, Meliaceae, Akariaceae. The other suborders of
the Geraniales are as follows: 2, Malpighiineae (3 families); 3,
Polygalineae (2 families); 4, Dichapetalineae (1 family); 5, Tricoccae
(2 families); 6, Callitrichineae (1 family). The order
Geraniales is preceded by the order Rosales (including 17 families,
among them Rosaceae and Leguminosae) and followed by the order
Sapindales (including 23 families, among them Anacardiaceae and
Sapindaceae).
The relationship of the orange subfamily to the six other subfamilies of the Rutaceae is
shown by the general key given by Engler (1931, pp. 105-11), which,
translated somewhat freely from the German, reads as follows:
Subfamily I. RUTOIDEAE.
Carpels usually 4-5, seldom 1-3 or more, often united only by the
common pistil and free below, at maturity more or less separated,
opening inward by splitting the follicle (loculicidal), usually with a
dehiscent endocarp, very seldom with 4-1 fleshy drupes
(Pitaviinae). Leaves and bark of twigs with schizolysigenous
oil glands. (5 tribes, 17 subtribes, 86 genera.)
Tribe (i) Xanthoxyleae.
Trees or shrubs, mostly small, greenish or greenish-white (seldom large
and clear white) flowers which are always actinomorphous (radial) and
often unisexual. Carpels only seldom with more than 2
ovules, Embryo [sic] mostly with flat cotyledons in endosperm (except Bosistoa and Pagetia). (5 subtribes, 30 genera.) Subtribe 1, Evodiinae (includes Xanthoxylon and Fagara) (20 g.), tropics and subtropics of Old and New Worlds; subtr. 2, Lunasiinae ( 1 g.), Monsoon region;1
subtr. 3, Decatropidinae (3 g.), Central America; subtr. 4, Choisyinae
(5 g.), Central America, Pacific Islands, and Australia; subtr. 5,
Pitaviinae (1 g.), Chile;
Tribe (ii) Ruteae. Herbs or perennial herbs, seldom shrubs, with medium-sized, always perfect flowers, which sometimes (Dictamnus) are slightly zygomorphic. Carpels as a rule with more than 2 ovules (only in Ruta in the subgenus Haplophyllum
with 2 ovules and occasionally indehiscent fruitlets).
Seeds with endosperm. (2 subtribes, 6 genera.)
Subtr. 6, Rutinae (5 g.), subtropical and temperate regions of Old and
New Worlds (includes Cneoridium, a California shrub); subtr. 7, Dictamninae (1 g.), temperate zone of Europe and Asia;
Tribe (iii) Boronieae.
Perennial herbs or shrubs. Carpels with only 1 or 2
ovules. Flowers always actinomorphic, mostly
perfect. Embryo usually straight, cylindrical, usually
immersed in abundant fleshy endosperm. (5 subtribes, 19
genera.) Subtr. 8, Boroniinae (6 g.), Australia and New
Caledonia; subtr. 9, Eriostemoninae (9 g.), Australia and New Caledonia;
subtr. 10, Correinae (1 g.), Australia; subtr. 11, Nematolepidinae (2
g.), Western Australia; subtr. 12, Diplolaeninae (1 g.), Western
Australia;
Tribe (iv) Diosmeae. Mostly perennial herbs and shrubs, seldom trees (Calodendrum),
always with simple leaves. Flowers almost always
actinomorphic, mostly perfect. Seeds without
endosperm. Embryo mostly straight with fleshy
cotyledons. (3 subtribes, 12 genera.) Subtr. 13,
Calodendrinae (1 g.) East Africa (Kenya) to Cape Province (South
Africa); subtr. 14, Diosminae (9 g.), Cape Province (South Africa);
subtr. 15, Empleurinae (2 g.), Cape Province (South Africa);
Tribe (v) Cusparieae.
Shrubs or tree. Flowers actinomorphic or the corolla and the
androecium zygomorphic. Seeds with little or no
endosperm. Embryo curved, the plumule lying between the
cotyledons. (2 subtribes, 19 genera.) Subtr. 16,
Pilocarpinae (3 g.), tropical America and subtropical South America;
subtr. 17, Cuspariinae (16 g.), tropical America, mostly Brazil and
northern South America.
Subfamily II. DICTYOLOMATOIDEAE.
Leaves with many-celled but not lysigenous oil glands.
Flowers actinomorphic. Stamens isomerous and alternate with
the petals, with bractlets at the base. Carpels united only
at the base, with several ovules. Fruits with dehiscent
endocarp, 3-4 seeded. Small trees with doubly pinnate
leaves. (1 tribe, 1 genus.)
Tribe (vi) Dictyolomateae. (1 genus.) Brazil and eastern Peru.
Subfamily III. FLINDERSIOIDEAE.
Trees or shrubs. Carpels 5-3, united, each with 2-8 ovules
in 2 rows. Fruit a loculicidal or septicidal capsule, with
persistent endocarp. Seed winged, without
endosperm. Leaves with lysigenous oil glands. (1
tribe, 2 genera.)
Tribe (vii) Flindersieae. (2 genera.) Eastern Australia, New Caledonia, East Indian Archipelago, Ceylon, and India.
Subfamily IV. SPATHELIOIDEAE.
Carpels 3, completely fused, each with 2 pendent ovules.
Fruit a winged drupe with a 3-loculed hard pit. With
oil-bearing secretory cells in the leaves, bark, and pith; lysigenous
oil glands in the leaf margins. (1 tribe, 1 genus.)
Tribe (viii) Spathelieae. (1 genus.) West Indies.
Subfamily V. TODDALIOIDEAE.
Carpels 5-2, incompletely or completely united, or else only 1, each
with 1 or 2 ovules. Fruit formed out of 4-2 drupelets united
only at the base, or which some occasionally abort, or else a drupe
with a thick or thin mesocarp and a thick or thin endocarp, or a dry,
winged, indehiscent fruit. Seeds with or without
endosperm. (1 tribe, 6 subtribes, 25 genera.)
Tribe (ix) Toddalieae.
(6 subtribes, 25 genera.) Subtr. 18, Phellodendrinnae (2
g.), temperate and subtropical eastern Asia and tropical Africa; subtr.
19, Sohnreylinae (1 g.), Amazon Valley, Brazil; subtr. 20, Pteleinae (4
g.), tropical and temperate America; subtr. 21, Oriciinae (2 g.),
tropical Africa; subtr. 22, Toddaliinae (13 g.), tropics, Old and New
Worlds (include Casimiroa, a Mexican and Central American fruit
tree); subtr. 23, Amyridinae (3 g.), northern South America, West
Indies, Central America, Texas, Florida, tropical Africa.
[The genus Amyris, having about 30 species native to Florida,
Texas, Mexico, Central America, West Indies, and northern South America,
is rather closely related to the tribe Clauseneae of the next
subfamily, Aurantioideae.]
Subfamily VI. AURANTIOIDEAE.
Fruit a berry [or hesperidium] with a leathery rind or hard shell, in
tribe Citreae often with pulp formed by juicy emergenzen that arise on
the carpellary walls. Seeds without endosperm, sometimes
with 2 or more nucellar [false] embryos. Leaves and bark [of
twigs and young branches] with schizolysigenous oil glands [small or
sometimes large trees, rarely shrubs.]; (2 tribes, 33
genera.) [This subfamily is given as classified by Swingle
for this chapter. Engler made a single tribe with 2
subtribes and with a total of 29 genera.]
Tribe (x) Clauseneae.
(3 subtribes, 5 genera.) Subtr. 24, Micromelinae (1 g.),
Monsoon region and western Polynesia as far as Tonga, Fiji, and Samoan
Islands; subtr. 25, Clauseninae (3 g.), Monsoon region and tropical
Africa; subtr. 26, Merrilliinae (1 g.), Malay Peninsula and Sumatra;
Tribe (xi) Citreae. (3
subtribes, 28 genera.) Subtr. 27, Triphasiinae (8 g.),
Monsoon region; subtr. 28, Citrinae (13 g.), Monsoon region and tropical
Africa; subtr. 29, Balsamocitrinae (7 g.), Monsoon region and tropical
Africa.
Subfamily VII. RHABDODENDROIDEAE.
Flowers with a bowl-shaped concave receptacle, with obliterated calyx, 5
petals, and very numerous stamens. Ovary free, ovoid,
1-locular, with 1 basal ovule. Pistil attached to the side
of the ovary, with a long lateral stigma. Fruits with thin
exocarp and thin endocarp. Leaves simple. (1
tribe, 1 genus.)
Tribe (xii) Rhabdodendreae. (1 genus.) Amazon Valley.
Total for the Rutaceae: 7 subfamilies, 12
tribes (containing 29 subtribes), with about 150 genera and 1,600
species.
THE ORANGE SUBFAMILY, AURANTIOIDEAE
The subfamily Aurantioideae is defined briefly above in the outline of the Rutaceae,
where all the subfamilies, tribes, and subtribes of this plant family
are given. All the species of the Aurantioideae are trees or
shrubs with persistent (evergreen) leaves except in the three monotypic
genera, Poncirus, Aegle, and Feronia, and in three species of Clausena (C. pentaphylla, C. dentata var. dulcis, and C. suffruticosa) and one of Murraya (M. alternans).
The flowers are usually white and very often fragrant. Many
of the genera bear subglobose fruits with a green, yellow, or orange
peel dotted with numerous oil glands that often give an agreeable aroma
when the fruit is handled. The fruits of the genus Citrus are among the most beautiful, most fragrant, and most delicious known to man. This subfamily contains Citrus and thirty-two other genera related more or less to Citrus, classed in two tribes and six subtribes which contain, as treated here, 203 species. The genus Citrus
and a few others closely related to it have fruits unlike any others
known to botanists in being filled with curious pulp-vesicles which
contain in many species a delicious juicy tissue. The
subtribe Balsamocitrinae, which belongs to the tribe Citreae, has fruits
as large as oranges or grapefruits but with a hard woody
shell. These hard-shelled fruits do not contain juicy
pulp-vesicles, although some of them are pleasantly aromatic and much
liked by both natives and Europeans in India and Indo-China.
Many of the remote relatives of Citrus belonging to the tribe Clauseneae have extremely small fruits very unlike those of Citrus and
usually semidry and entirely inedible. Nevertheless some of
these remote relatives have been found to be graft-compatible with Citrus.
The native habitat of the subfamily
Aurantioideae is limited to the Old World. Most of the
genera are found in the Monsoon region from West Pakistan to
north-central China and thence south through the East Indian Archipelago
to New Guinea and Bismarck Archipelago, northeastern Australia, New
Caledonia, Melanesia, and the western Polynesian islands. Of
the thirty-three genera that constitute the Aurantioideae, no fewer
than twenty-nine are native to the Monsoon region and twenty-seven of
them are found only there. Five genera, belonging to two
tribes and to three subtribes, are native to tropical Africa and four
genera are found only there. Only one genus, Clausena, is native both to the Monsoon region and to tropical Africa. Many of the species of Citrus and of the genera closely related to Citrus are now found in cultivation or are grown for ornament in all the tropical and subtropical regions of the world.
Tribes, Subtribes, and Genera of the Subfamily Aurantioideae
The thirty-three genera of the subfamily
Aurantioideae are divided naturally and easily into two tribes: the
Clauseneae, with five genera, including the remote relatives of Citrus; and the Citreae, with twenty-eight genera, including Citrus
and all its closer relatives. Each of these two tribes is
divided into three subtribes, making six in all. Keys are
given to separate the two tribes and also the subtribes [e.g., Clauseneae; Citreae].
As these tribes and subtribes are
frequently referred to in discussing relationships, English phrases have
been applied to them, in addition to their technical Latin names, that
will, it is hoped, suggest rather definitely the degree of relationship
of each tribe or subtribe to Citrus.
The natural order of the tribes and
subtribes of the orange subfamily is from the most simple to the most
specialized, as shown in the list,
except that the subtribe Balsamocitrinae, although comprising species
somewhat less highly specialized than those in the subtribe Citrinae,
has been placed at the end of the series. This has been done
to avoid intercalating the subtribe Balsamocitrinae between the
subtribes Triphasiinae and Citrinae, an arrangement which would have
obscured the close relationship clearly exhibited by some of the genera
of Triphasiinae with some of the more primitive genera of
Citrinae. The list
gives the number of groups under each subtribe, as well as the number
of genera. The genera having only one species (monotypic)
are marked with an asterisk; the number of species and varieties in
other genera is given after the genus name in parentheses.
TRIBE I. CLAUSENEAE: VERY REMOTE AND REMOTE CITROID FRUIT TREES
The tribe Clauseneae includes the more
primitive genera of the orange subfamily. None of the
species develop spines in the axils of the leaves and the odd-pinnate
leaves are at once distinguished from those of the tribe Citreae by
having the leaflets attached alternately to the rachis, which does not
break up into segments when the leaves fall; rachises are not winged
(except in Merrillia caloxylon, Murraya alata, M. alternans, Clausena guillauminii, C. wallichii,and C. luxurians).
Trifoliolate leaves are rarely found
exclusively on any species but occur sporadically merely by reduction of
odd-pinnate leaves to trifoliolate leaves, often on the same
plant. Such trifoliolate leaves do not show clearly the
precise pairing of the lateral leaflets that is always shown in the
tribe Citreae. The leaves of plants of the tribe Clauseneae
do not show the winged petioles often found in members of the tribe
Citreae (except very narrow wings on the six species noted above).
The ovary has two to five locules with only one or two ovules in each locule, except in Merrillia,
which has five (rarely six) locules and eight to ten ovules in each
locule. The fruits are usually small semidry or juicy
berries, except in Merrillia, which has ovoid fruits the size of a lemon, with a tough leathery peel. The mature ovaries and young fruits of Micromelum have
the locule walls convolute. This genus has the petals
valvate in aestivation, differing thereby from all the other genera of
the subfamily.
The bundle traces which enter the sepals
and petals in plants of the tribe Clauseneae were found by Albert H.
Tillson (1938, p. 9; Tillson and Bamford, 1938, p. 783) "to arise
independently from the axis and to display no trace of fusion with each
other." In the tribe Citreae only three of the twenty-four genera which he studied fail to show such fusions.
Only a few genera (five in all) have been
established in this tribe, whereas the tribe Citreae has
twenty-eight. Seventy-nine species are listed here in the
tribe Clauseneae and 124 in the tribe Citreae, but the largest genus of
the tribe Clauseneae, namely, Glycosmis, for which thirty-five species have been named, is still only imperfectly known.
The tribe Clauseneae falls into three very natural subtribes, as is shown by the key.
Subtribe 1. Micromelinae: Very Remote Citroid Fruit Trees
The subtribe Micromelinae contains only one genus, Micromelum,
with some nine or ten species, many of them very much alike and rather
hard to distinguish. All the species have odd-pinnate leaves
with alternate leaflets borne on a nonarticulated rachis, except M. diversifolium,
which has trifoliolate or unifoliolate leaves. The
inflorescences are corymbose-paniculate, often very large and usually
flat-topped, often surrounded by leaves much larger than even the
largest inflorescences.
The leaves of Micromelum are very similar to those of Clausena and Murraya, to which genera specimens of Micromelum are
sometimes assigned, even by experienced collectors and also by
experienced botanists. The flowers, ovaries, and seeds are,
however, very different. The petals of Micromelum are
valvate, not imbricate, and the cotyledons are flat and folded, not
thick and plano-convex as in all other genera of the subfamily
Aurantioideae. The ovaries show a curious twisting of the
radial follicle walls, also unique in the orange subfamily.
These remarkable diversities in
characters are of much taxonomic importance and are proof of the ancient
origin of Micromelum, a view also supported by the very wide
distribution of the genus in the Monsoon region, much farther to the
eastward in a truly indigenous state than any other genus of the orange
subfamily.
I. Micromelum Blume
I. Micromelum Blume, Bijdr. Fl. Nederl. Indie 3:137. 1825; nomen conservandum, Intern. Congr. Bot. 1930. Aulacia Lour. Fl. Cochinch. 1:273. 1790.
Type species.—Micromelum pubescens Blume.
Distribution.—Northeastern India; Burma to Australia and New Caledonia; Fiji, Tonga, and Samoan islands in western Polynesia.
Small spineless trees; leaves odd-pinnate (rarely 3-foliolate or 1-foliolate in M. diversifolium);
leaflets thin, alternate on wingless rachis; inflorescences usually
large, terminal corymbose panicles often flat-topped; flowers small,
5-merous (except the stamens, which are twice as many as the petals);
petals valvate in the bud; ovary with 2-6 (usually 3-5) locules with 2
superimposed ovules in each locule; style rather slender, narrowed at
the base and articulated with the ovary, deciduous; radial walls of the
locules usually (always?) curved as if twisted during development by a
rotation of the outer wall of the ovary with reference to the axis;
seeds with thin, folded cotyledons; fruits subglobose or ovoid, dry
berries with a gland-dotted peel.
Oliver (1861, p. 19) gave the following excellent sketch of the morphology of the genus Micromelum: "…The essential characters of the genus [Micromelum]
rest especially in the broad, foliaceous, and remarkably
contortuplicate cotyledons; perhaps, also, in the singular torsion of
the dissepiments of the ovary, which in M. pubescens, is usually
apparent immediately after the fall of the floral whorls.…The fruit is
but 1- (or 2-) seeded, and the twisted dissepiments with the empty
loculaments are soon closely pressed to one side by the young
seed. The style is minutely constricted and articulated at
the base ovary. In M. pubescens the ovary is very
usually 5-locular; in Ceylon and Java specimens I have found an
exceptional 6th cell; in the Australian plant from Port Essington, etc.,
it varies, 4, 5 or 3. M. molle Turcz., I have found
to be 4-locular, but probably it also varies. The peculiar
features which I have remarked of the ovary and seed are associated with
other common characters.…These are especially the truly valvate or
obliquely valvate aestivation of the corolla, and the terminal cymose
corymbs of numerous flowers—as in Murraya seldom or never having the central axis of inflorescence elongated as it is in the paniculate Clausenae…"
The genus Micromelum ranges from
the Samoan, Fiji, and Tonga islands to Australia and New Guinea, through
the East Indian Archipelago to the Philippines, Indo-China, southern
China, Ceylon, northeastern India, and West Pakistan. One
species, M. minutum, ranges farther eastward into Polynesia than
any other species of the orange subfamily and also occurs in New
Caledonia, Australia, the Philippines, and Indo-China. The
other species have a more restricted range, and one, M. ceylanicum, is restricted to the island of Ceylon and another, M. diversifolium, is found only on Halmahera Island and its near-by companion, Batjan Island, in the Moluccas.
THE SPECIES PROBLEM IN MICROMELUM
The number of species of Micromelum
is not large—nine are here recognized—but they can be described or
keyed out only with difficulty because apparently all the species are
greatly variable, usually not merely in one, or in a few, but in many
characters. A cursory glance at the literature of the genus
shows that taxonomists are by no means agreed on the number of species,
or on the characters that define species, or on the areas they occupy.
Fortunately, new characters are being
found that promise to make possible the satisfactory definition and the
easy recognition of the species when adequate material is
available. One of the most striking of these new characters
is the presence of large or small oil glands that are found, usually one
above each locule, at the tip of the ovary. Very large oil
glands expand greatly the ovary tip of M. falcatum; large oil glands occur in M. compressum but do not noticeably expand the ovary tip; whereas only very small oil glands are found similarly placed in M. pubescens.
These new characters, and others already used by taxonomists, may be seen in figure 3-1, which shows microphotographs of longitudinal or cross sections of ovaries of eight of the nine species of Micromelum. A key to the species of Micromelum is presented.
1. Micromelum pubescens Blume, Bijdr. Fl. Nederl. Indie 3:138. 1825. Illus. Engler, Die Nat. Pflanzenfam. 3(4):186, fig. 107,A-K. 1896; fig. 3-1,D this work.
Type.—Java (Blume). Rijks Herb., Leiden.
Distribution.—Java, Sumatra, Andaman Islands, southern Burma, Malaya, Palawan Island, P.I.
A brief description by Koorders (1912,
vol. 2, p. 424), based on material from Java, the type locality, reads,
translated, as follows: "Tree, up to 6 m high, or erect
shrub. Leaflets 7-11, alternate, soft-pubescent below,
obliquely ovoid to broadly lanceolate, 3-17 X 2-7 cm. Fruit
6-8 mm long, orange-yellow." Ridley (1922, vol. 1, p. 352)
describes this species as follows: "Large shrub or treelet.
Branchlets and leaf-rachis puberulous but eventually
glabrescent. Leaves 6 to 18 in. long; leaflets 9 to 15,
alternate, lanceolate or ovate-acuminate, edges undulate, base slightly
narrowed oblique; nerves 9 to 12 pairs, 1.5 to 3.5 in. [3.8-8.8 cm]
long, 0.5 to 2 in. [1.3-5 cm] wide; petioles up to 3 in. [7.6 cm]
long. Cymes 6 to 8 in. [15-20 cm] across, peduncled,
many-flowered [pubescent]. Flowers 0.25 to 0.5 in. [6-13 mm]
long, greenish-white. Calyx 5-toothed. Ovary
pubescent. Berry ovoid to oblong, glabrescent, orange, 0.3
to 0.4 in. [7.5-10 mm] long."
The chief diagnostic characters of this species are given in the key. The pistil (fig. 3-1,D)
is of medium size with a rather long style in proportion to the
ovary. The oil glands at the tip of the ovary, one over each
locule, are unusually small and sometimes difficult to
detect. Tanaka (1931b, pp. 2, 3) contrasted this species with M. minutum, as follows: M. pubescens has (1) much larger floral organs than M. minutum;
(2) stouter peduncles; (3) thicker leaflets; (4) ovary longer stalked;
(5) flower buds much broader and silvery pubescent, instead of
golden-yellow pubescent as in M. minutum. From M. compressum of the Philippine Islands, Tanaka reported that it differs in four characters (see next species below).
2. Micromelum compressum (Blanco) Merr. Sp. Blancoanae 200. 1918. Bergera compressa Blanco, Fl. Filip. 361. 1837; Micromelum tephrocarpum Turcz. Bul. Soc. Nat. Mosc. 31:379. 1858. Illus. fig. 3-1,G.
Type.—Philippines, Luzon Island (Blanco). Original type lost. Substitute type: (Merrill, Species Blancoanae, No. 884).
Distribution.—Philippines: Luzon to Mindanao (and Palawan?) Islands.
The best description yet published of
this species is apparently Turczaninow’s original diagnosis of his M. tephrocarpum,
which, translated, reads as follows: "Unarmed, very glabrous; leaves
odd-pinnate, leaflets alternate, lanceolate, obtusely acuminate [at the
tip], attenuate, inequilateral at the based, entire or slightly
serrulate, pellucid-punctate; panicles terminal, much shorter than the
leaves; fruit ovoid-oblong, acute, becoming cinereous-blue, with fewer
than 3 seeds; calyx truncate, somewhat recurved, half as long as the
petals; alternate filaments shorter, anthers adnate, subglobose; ovary
seated upon a very short disk, style rather thick and terminated with a
capitate stigma; fruit (‘berry’) with the locule walls contorted and
twisted (‘contortuplicate’), 5-loculed, with only 3 seeds in the
immature fruit [which is] obovate-oblong, and flattened.
From M. glabrescens Benth. it seems to differ chiefly in having fruits with attenuate tips."
A flowering specimen collected by M.
Ramos at Bohol, Luzon, P.I. (Bur. Sci., No. 42570), in the herbarium of
the Arnold Arboretum, shows very small pistils only 2-3 mm long, with
the ovary 1-1.2 mm long, and the style about equaling the ovary in
length, faintly furrowed longitudinally, and abruptly contracted at the
base where it joins the ovary, about 0.4 mm diam., stigma hemispherical,
0.8 mm diam.
Tanaka, who has given much attention to distinguishing the species of Micromelum
and has examined carefully the extant type specimens, has noted certain
contrasts he observed between the species. He stated (1931b, pp. 2, 3) that M. pubescens, common in Java, Sumatra, and north to southern Burma, differs from M. compressum:
(1) in having more slender flower buds covered with very short silvery
pubescence; (2) in its hairy ovary; (3) in its glabrous pedicels; (4) in
it's smaller, narrower leaflets with many more lateral veins.
2a. Micromelum compressum var. inodorum (Blume) Tan. Trans. Nat. Hist. Soc. Formosa 22:418. 1932. Bergera inodora Blanco, Fl. Filip. 360. 1837; Micromelum molle Turcz. Bul. Soc. Nat. Mosc. 31:380. 1858.
Type.—Philippines (Cuming, No. 1056). Not located. Substitute type: (Merrill, Species Blancoanae, No. 719). Herb. Bur. Sci., Manila.
Distribution.—Philippines; doubtfully reported from Celebes by Tanaka (1932e, p. 419).
Turczaninow's original diagnosis of M. molle (an undoubted synonym of Blanco's Bergera inodora)
reads, translated, as follows: "Unarmed; twigs, petioles, peduncles,
panicles, calyxes, and petals [covered with] short, soft pubescence;
leaves odd-pinnate, 7-13-foliolate; leaflets alternate,
ovate-lanceolate, acuminate [at the tip], attenuate, inequilateral at
the base, densely and softly pubescent on both sides on the midrib and
veins, sparingly pubescent between the veins; panicles composed of both
axillary and terminal [portions] shorter than the leaves; calyx
truncate, slightly 5-toothed, much shorter than the petals; fruits
acute, 1-3 seeded, blackish-blue, glabrous. From M. pubescens Bl.,
of which a specimen was sent by Blume himself to the [Museum]
Schultesium, it differs in being more pubescent, in having larger and
softer [pubescent], acutely acuminate leaflets, and in having fruits
acute, not very obtuse."
Tanaka stated (1932e, p. 418):
"All botanical characters agree with the type species except the
pubescence of the leaf and the shoot." He also noted the
short, thick flower buds in contrast with the small, slender flower buds
of M. pubescens and M. minutum.
3. Micromelum scandens Rechinger, Denkschr. Akad. Wiss. Math.-Naturw., Wien 89:564. 1914. Micromelum minutum var. intermedium Tan. Med. Rijks Herb. Leiden 69:2. 1931. Illus. Tillson & Bamford, Amer. Jour. Bot. 25:782, figs. 1-11. 1938; fig. 3-1,F this work.
Type.—Bismarck Archipelago, New
Britain Island, Gazelle Peninsula, Baining Mountains (Rechinger, No.
3675). Herb. Naturhist. Mus., Vienna.
Distribution.—Bismarck Archipelago and Melanesia.
The original description reads,
translated, as follows: "A climbing [or clambering] shrub; leaves
pinnate, leaflets large, 15-20 X 6-7 cm, with entire margins,
brownish-black when dried; fruits dry berries, disposed 30-40 in cymes,
with spirally twisted follicle walls, 8-12 mm long, glabrous, with many
small pits, black when ripe, with a short fragment of the style at the
tip, and the flat cupulate calyx, with an almost entire margin,
persistent at the base."
The type specimen of M. scandens shows one leaf 22 X 8 cm, larger than any yet measured of M. compressum, with 10 pairs of lateral veins; the leaflets of M. scandens are acuminate at the tip and have 1/5-1/4 more lateral veins than those of M. compressum,
and they arise at a somewhat smaller angle with the midrib.
The persistent calyx is shallow, cupulate with indistinct
lobes. The pedicels of the fruits are 7-11 mm long, with 2
small bracts near the base.
A specimen in fruit collected on
Bougainville Island on May 25, 1930, by Kajewski (No. 1785) has a
terminal fruit cluster with very stout lower branches 2.5-3.5 mm in
diameter. The notes state that the fruits are "dark red when
ripe, oblong coming to a blunt point, length 1.4 cm, diameter 8
mm." Very young fruits are 3.5-4 X 1.2-1.5 mm, cylindrical,
rounded at both ends and show a few scattered, slender, white
hairs. The nearly ripe fruits are glabrous, rough with oil
glands, and show at the tip a very short truncate style base 0.7-0.8 mm
in diameter.
One of the specimens collected by
Kajewski in 1930 (No. 1654, from the Pupei Gold Fields, Bougainville
Island) was from a tree growing up to 18 m high. The
specimen has very large, lax, more or less leafy inflorescences with
long nodes below, much like those shown by the type specimen of the
species. The flower buds are oval or broadly and shortly
elliptical, 5-6 X 2-3 mm, decidedly larger than those of good material
of M. minutum from Tonga, the type locality, and from Fiji, New
Caledonia, and Australia. This specimen (Kajewski's No.
1654) had a flower just ready to open; its pistil is 4.2 mm long when
dry, ovary almost glabrous. The calyx is large and expanded
until it is shaped like a shallow saucer, nearly pentagonal in outline.
Swingle considered M. minutum var. intermedium
Tan. from New Ireland, Bismarck Archipelago (to judge from a photograph
of the types specimen sent him by Tanaka), to be a fairly typical form
of M. scandens, which was based on a specimen collected by
Rechinger in the adjoining island of New Britain, the eastern-most point
of which is distant only some 35 kilometers from the west shore of New
Ireland. Bougainville Island lies only some 200 kilometers
southeast of the southern end of New Ireland. Tanaka had not
seen the excellent material of Micromelum from the Solomon Islands in the Arnold Arboretum herbarium when he allocated just such a form to M. minutum as a variety. Tanaka, who examined the type specimen of M. scandens at Vienna, stated (1931b, p. 3) that it is very different from M. minutum and most like M. compressum. This species appears to be a good one, but needs further study.
4. Micromelum falcatum (Lour.) Tan. Bul. Mus. Hist. Nat. Paris, 2 sér. 2:157. 1930. Aulacia falcate Lour. Fl. Cochinch. 1:273. 1790; Cookia falcate DC. 1824; Micromelum octandrum Turcz. 1863. Illus. fig. 3-1,C.
Type.—French Indo-China, Annam (?) (Loureiro). Herb. Brit. Mus.
Distribution.—North Vietnam, South Vietnam, Cambodia, Laos, Burma, Andaman Islands, Thailand, southern China.
Guillaumin (1911, p. 649) described this species (under the name M. pubescens Bl.)
as follows: "Shrubs or small tree, twigs woolly-pubescent, then
glabrescent. Leaves yellowish-green in color, 15-31 cm long,
odd-pinnate; leaflets 7-9, lanceolate, inequilateral at base,
long-acuminate-pointed, margins slightly crenulate, glabrous, except for
the midrib above and the larger veins below [which are pubescent],
lateral veins 6-8 on each side, prominent below, veinlets not visible;
petiolules and petioles cylindric, pubescent, 4-10 mm long.
Inflorescences pubescent, shorter than the leaves; pedicels woolly, 5 mm
long, having two small opposite hairy bracts toward the base; flowers 5
mm long, greenish-white; calyx woolly with 5 very short teeth; petals
5, long-elliptic, glabrous or glabrescent, 5 mm long; stamens 10, free,
glabrous, the largest as long as the petals; filaments subulate; disk
short, glabrous, grooved; ovary ovoid, velvety-hairy; style caducous,
elongated, glabrous; stigma capitate; locules 5, with 2 ovules in each;
fruit ellipsoid, fleshy, with numerous oil glands, glabrous; segments
often 2-3, each with a single seed. Flowers
Dec.-Jan. Very common."
This species differs from all others in
the genus in having very narrow, often falcate, long-acuminate leaflets,
very unequal-sided at the base, usually 4 to 11 by 1.5 to 3 cm,
including petiolule 3 to 5 mm long. It also is the only Micromelum
having the top of the ovary much broadened by large oil glands, found
one over each locule. This plant was the first species of
the genus to be described (as Aulaciafalcate in 1790), and Loureiro's genus Aulacia antedates Blume's Micromelum by thirty-five years. However, the genus Aulacia
was not understood by botanists in spite of the fact that a specimen of
it, one of the few remaining types of Loureiro's species, is preserved
in the British Museum at London. In 1919, Merrill (in a MS
study on Loureiro's types) concluded that Aulacia was a synonym of Micromelum, but the Fifth International Botanical Congress, meeting at Cambridge in 1930, conserved the name Micromelum and rejected the older generic name Aulacia (Merrill, 1935, p. 221).
5. Micromelum ceylanicum Wight, Ill. Ind. Bot. 1:109. 1840. Illus. fig. 3-1,A.
Type.—Ceylon (Wight, No. 1836). Herb. Kew.
Distribution.—Found only in Ceylon.
Trimen (1893, vol. 1, p. 218) described this species (under the name M. pubescens)
as follows: "A small tree, shoots very finely and densely pubescent;
leaves imparipinnate, 8-10 in. [20-25 cm long], rachis pubescent;
leaflets 9-15, alternate or subopposite, shortly stalked, 1 1/2-3 in
[3.8-7.5 cm long], very oblique base, ovate-lanceolate attenuate,
obtuse, irregularly finely crenate and wavy, with very numerous, rather
conspicuous glands, glabrous above, nearly so or slightly pubescent
beneath; flowers 1/4 - 1/2 in. [6-13 mm diam.], very shortly stalked,
arranged in terminal and axillary, spreading, pubescent, dichotomous,
carymbose cymes, bracts small, opposite at the bifurcations; calyx lobes
broad, triangular, pubescent; petals oblong-linear, spreading,
pubescent; ovary oblong, very pubescent; style rather longer, very
thick, stigma capitate; fruits 3/8 in. [9 mm] long, oblong-ovoid,
pointed, rough with glands, glabrous, yellow."
This species, as can be seen in figure 3-1,A has calyx lobes extending to the middle of the ovary in a nearly full-grown flower bud. The other species of Micromelum would not show the sepals in a section made at this level.
In Ceylon this species is said to be
rather common "in the low country, especially in the dry
region." The name of the species in Singhalese is walkarapincha. Murraya koenigii is called karapincha in Singhalese and Clausena indica is called mogen-karapincha. Both plants look so much like M. ceylanicum as to be easily confounded with it, according to Trimen (1893, p, 219).
6. Micromelum integerrimum (Buch.-Ham.) Roem. Syn. Hesper. 1:47. 1846. Bergera integerrima Buch.-Ham. ex Coleb. Trans. Linn. Soc. London 15:367. 1827; B. integerrima Roxb. ex DC. nomen semi-nudem. 1824. Illus. Beddome, Fl. Sylv. Anal. Gen. xliii-xliv, pl. 7 (flowers only). 1871; fig. 3-1,E this work
Type.—British India, Cult. Hort. Bot., Calcutta (Roxburgh). Herb. Brit. Mus.
Distribution.—Northeastern India: West Bengal, Sikkim, Assam; Nepal; Burma; East Pakistan; Andaman Islands.
Kurz (1877, vol. 1, pp. 186, 187) described this species, under the name M. pubescens,
as follows: "An evergreen [shade-loving] tree, 25-30 ft. [7.5-9.14 m]
tall, with a clean trunk 10-12 ft. [3-3.66 m], measuring 2-3 ft. [60-90
cm] in girth, all younger parts more or less densely puberulous; bark
about a line thick, whitish, somewhat roughish; cut pale-coloured;
leaves unequally pinnate, puberulous or glabrous, 1 1/2 ft. [46 cm]
long, the rachis usually more or less puberulous; leaflets in 3-7 pairs
with an odd one, alternating or nearly so, oblong-lanceolate to broadly
lanceolate, oblique at base, shortly petioluted, 5-7 in. [12-18 cm]
long, acuminate, usually somewhat waved, entire or nearly so; flowers
middling-sized, whitish, on short pedicels, forming terminal divaricate
or crowded pale tawny appressed-pubescent corymb-like panicles; calyx
more or less obsoletely 5-teethed, pubescent; petals about 2 1/2 lin. [5
mm] long, pubescent glabrescent; berries seated on short, stalk-like
torus, ovoid-oblong, also when young , glabrous, gland-dotted, yellow,
turning dull orange-red, terminated by the style scar."
H. H. Haines, the former Conservator of
Forests of Bihar and Orissa (northeastern India) in his discussion of
this species (1921, p. 164), under the name M. pubescens stated:
"A small tree…leaves 8-18" [20-46 cm] long, with 5-11 very large
leaflets and large corymbs of white flowers 0.5" [13 mm] diam., which
are succeeded by foetid, ovoid, yellow or scarlet berries 0.5" [13 mm]
long.…Leaflets ovate to lanceolate or elliptical-oblong, attaining 8" by
3.5" [20 X 8.8 cm], lowest sometimes only 1.5" [4 cm].…Corymbs
pubescent or tomentose, often 1 ft. [30.5 cm] across…very pretty when in
flower or fruit."
The flowers and especially the pistils of
this species are decidedly larger than those of all the other known
species of Micromelum. The fruits are attenuate at the base, instead of broadly rounded as in M. hirsutum and
several other species. A specimen from the South Andaman
Islands, secured by King's collector in North Corbyu's Cove, now in the
herbarium of the Arnold Arboretum (Tanaka's Ident. No. A 64), shows (in
the dry state) pistils 7 to 8 mm long; ovary 2 mm long; style 3 mm long
with many fine longitudinal furrows; stigma 1 mm high; the attenuate
base of the ovary (disk?) 1.5 mm high. Because of a long
series of errors in citation, the botanical name of this species has
never yet been correctly accredited either as Bergera integerrima or as Micromelum integerrimum. Bergera integerrima was first published in 1827 by Colebrooke, who accredited it to Buchanan-Hamilton. It was transferred to Micromelum as a species distinct from M. pubescens by Roemer in 1846, a transfer incorrectly accredited to Wight and Arnott, who merely excluded it from Bergera but did not recognize it as a valid species of Micromelum.
7. Micromelum hirsutum Oliv. Jour. Linn. Soc. Bot. 5(2):40. 1861. Illus. Guillaumin, in Leconte, Fl. Gén. Indo-Chine 1:646, fig. 68(8-10). 1911; fig. 3-1,H this work.
Type.—Malay Peninsula, Penang (Wallich, No. 8516). Herb. Kew.
Distribution.—Burma, Andaman Islands, Thailand, North Vietnam, South Vietnam, Cambodia, Lao.
Oliver's original diagnosis of this
species reads in part, translated, as follows: "Leaflets 15-23, very
asymmetrical at the base; calyx small, with 5 triangular lobes; petals
hirsute without; ovary 5-locular; stigma almost as long as the style;
leaves 10-16 in. [25-41 cm long]; leaflets trapezoid-lanceolate or
ovate-lanceolate, often not a little acuminate, somewhat obtuse at apex,
margins slightly denticulate, sparsely pilose or glabrescent below,
pilose or hirsute particularly near the rib and veins above.
Inflorescences divaricate cymes, corymbose or subpaniculate,
hirsute. Pedicels very short. Petals narrow or
linear-oblong. Fruit (young) ovoid-oblong, hispid, shortly
and narrowly stipitate. Chiefly differing from M. pubescens in the long leaves with very numerous leaflets, small calyx, and petals strongly hairy externally."
Kurz (1877, vol. 1, p. 187) added many
details to Oliver’s technical diagnosis, as follows: "A low, meagre,
often simple-stemmed shrub, about 2-3 ft. [60-90 cm] high, rarely
higher, all parts more or less shortly tawny hirsute or puberulous
(rarely almost glabrous); leaves unpaired-pinnate, densely puberulous;
leaflets in 5-10 pairs with an odd one, lanceolate or oblong-lanceolate,
shortly but slenderly-petioluled, very oblique at base, acuminate,
obsoletely repand-serrate, usually 3-5 in. [7.6-12.7 cm] long; flowers
small, whitish, on short hirsute pedicels, forming more or less shortly
tawny hirsute corymb-like panicles at the ends of the branchlets and in
the axils of the upper leaves; calyx shortly tawny hirsute, deeply
5-lobed; petals hardly 2 lin. [4 mm] long; ovary densely tawny hirsute;
berries sessile or nearly so, oblong or obovoid, especially while young
more or less puberulous, gland-dotted, crowned by the style scar."
"Hab.—Very frequent in the drier
upper-mixed forest, and the dry and low forests, all over Burma from Ava
and Pegu down to Tenasserim."
King (1894, p. 219) added other details:
"Leaves 6-12 in. [15-30 cm], rarely 15 in. [38 cm] long; leaflets 9-25,
1.5-3.5 in. [4-9 cm] long, 0.8-1.5 in. [2-4 cm] wide; main nerves 5-10
pairs. Cymes terminal, very tomentose, often lax, 6-8 in.
[15-20 cm] in diameter but sometimes condensed and only 2 in. [5 cm] in
diameter."
This species differs chiefly from the other species commonly occurring in Burma (M. integerrimum, but called M. pubescens by
King and Kurz) in being a small shrub, never a tree, and in being more
pubescent, especially the fruit, and in having smaller
flowers. Kurz noted that the fruits of M. hirsutum are puberulous and almost sessile, whereas those of M integerrimum (his M. pubescens)
are short-stalked, glabrous berries. Guillaumin (1911, pp.
649-50) noted that in Indo-China this species has "ellipsoid, fleshy,
reddish, glabrescent or pubescent fruits."
8. Micromelum minutum (Forst.) Wt. & Arn. Prodr. Fl. Pen. Ind. Or. 1:94. 1834. Limonia minuta Forst. f. Prodr. 33. 1786; Micromelum glabrescens Benth. Hook. Jour. Bot. 2:212. 1843; M. pubescens var. glabrescens (Benth.) Oliv. 1861; Glycosmis subvelutina F. Muel. 1858. Illus. Banks & Solander, Bot. Capt. Cook's Voy. 1:14, pl. 36. 1900; partly reproduced in fig. 3-2 this work; also fig. 3-1,B.
Type.—Friendly Islands (Forster). Herb. Brit. Mus.
Distribution.—Samoa, Tonga, Fiji,
New Caledonia, northeastern Australia, Melanesia, Bismarck Archipelago,
New Guinea, and north to the Philippines, Sumbawa, and Borneo; also
Annam (fide Tanaka).
This species was described, under the name M. glabrescens,
in 1843 by Bentham from material collected in the Friendly Islands (the
type locality) by Barclay, as follows: "Young leaves and inflorescences
finely tomentose, leaflets 10-12, obliquely ovate-acuminate, minutely
crenulate, adult leaves glabrous; calyx very short, 5-toothed; fruit
oblong, very obtuse. This is evidently very near M. pubescens
Blume; does not quite agree with his [Blume’s] very short
description. The leaflets are quite smooth, except in a very
young state. The inflorescence is a dichotomous
many-flowered terminal cyme. The flowers appear very small,
but are as yet unexpanded in the specimen before me. The
fruit is about 4 lin. [8 mm] long. The foliaceous cotyledons
are very broad, deeply emarginate and twisted, with rather a long
straight radicle." An examination of material from the type
locality (Tonga Islands), from Samoa, and from the Solomon Islands shows
the following characters in the dry state. The specimen
from the Tonga Islands (coll. by H. E. Parks, No. 16281, June-July,
1926, at Eua Island, now in U.S. Natl. Herb., No. 1528543) has very
short pistils, only 2 mm long; the ovary is 1.3 mm long, sparingly
covered with short gray hairs; the style and stigma measure 0.8 mm, the
style is glabrous above, somewhat hairy below. The specimen
from the Solomon Islands (coll. by Kajewski, No. 2371, December 15,
1930, now in Herb. Arnold Arbor.) shows pistils 3.5 mm long, with the
ovary 1.5 mm long, style and stigma 1.5 mm long. The ovary
is fusiform, narrowed at both ends, where it joins the disk below and
the style above, and has scattered yellowish hairs that soon fall
off. The style is sparingly hairy, not evidently furrowed
longitudinally, sharply constricted at the base and expanded into the
flattened, discoid stigma, about 0.6 mm wide and 0.3 mm
tall. The specimens from Tutuila, Samoa (coll. by W. A.
Setchell, No. 257, now in Herb. Arnold Arbor.), show pistils 3 mm long;
ovary 1.25 mm long, covered with rather sparse, short, gray or yellowish
hairs; style and stigma 1.2 mm long; style with similar hairs at the
base concealing the constriction at the base, if present; stigma
subglobose, 0.7 mm. diam.
This species has the smallest flowers
and, in particular, the shortest pistils of any species of the
genus. It ranges farther east in Polynesia than any other
species belonging to the orange subfamily. It alone reaches
the Tonga and Samoan Islands. It also ranges far to the
north, from northeastern Australia through New Guinea, Celebes, the
Philippines, and reaches North Borneo and Sumbawa, but not Java and
Sumatra according to Tanaka (1931b, p. 2), who stated, moreover, that Annam (Vietnam) is its westernmost limit.
As is to be expected from its very wide
distribution, this species varies considerably even in such important
organs as the pistil. Only two varieties have been published
as yet, but others could probably be made with equal justification.
8a. Micromelum minutum var. tomentosum Tan. Trans. Nat. Hist. Soc. Formosa 22:419. 1932.
Type.—Timor (Forbes, No. 3753). Herb. Brit. Mus.
Distribution.—Timor; Philippines: Mindoro and Luzon islands.
Tanaka's original description of this variety, translated, reads as follows: "Similar to Micromelum minutum in the appearance and size of its flowers and fruits but all parts completely covered with soft, golden yellow tomentum."
8b. Micromelum minutum var. curranii (Elm.) Tan. Trans. Nat. Hist. Soc. Formosa 22:419. 1932. Micromelum curranii Elmer, Leafl. Phil. Bot. 2:480. 1908; M. caudatum Merr. Phil. Jour. Sci. 27:26. 1925.
Type.—Philippines, Luzon Island, Baguio (Elmer, No. 8530). Herb. Bur. Sci., Manila.
Distribution.—Philippines: Bontoc, Benguet, and Union provinces of Luzon Island, at 1,200-1,450 m altitude (fide Merrill, 1923, vol. 2, p. 335).
Elmer's original description of his M. curranii (now reduced to a variety of M. minutum)
reads as follows: "Shrub, with rather numerous branchlets; wood hard,
covered with grayish-white mottled bark. Leaves crowded on
the young twigs, numerous, alternate, ascending, the peduncle [petiole]
short yellowish pubescent when young but soon becoming glabrous;
leaflets alternatingly scattered along the rachis, glabrous when mature,
unequal in size, ovate to broadly lanceolate, submembranous, entire or
obscurely apiculate, apex gradually acuminate, base obliquely rounded to
subacute, drying brown, paler beneath, the larger blades 7 cm long by 2
cm wide; petioles [petiolules] 3 to 5 cm long, when young short
yellowish pubescent but becoming glabrous; nerves 3 to 5 pairs,
ascending, more prominent beneath, reticulations not
visible. Corymbose panicle terminal, 6 cm wide across the
top, about as long; peduncles and pedicels strict, suberect, pubescent
when in flower, becoming glabrous when in fruit, the latter about 3 to 5
mm long; calyx truncate or obscurely 5-apiculate, rim-like or
saucer-shaped, pubescent when young, persistent and glabrous in fruiting
state; petals 5, ligulate, rather thick, glabrous or sparsely pubescent
on the outer side, 4 mm long, at least 1 mm wide, apex acute,
deciduous; stamens in one series, about 9, inserted upon a prominent
disk at the base of the ovary, easily detached; filaments subglabrous,
fleshy and more or less flattened, pointed at the apex, subequal in
length, the longer ones 4 mm in length; anthers basifixed, broadly
cordate or subelliptic, nearly as wide; style thick, 1 mm long, bearing a
terminal subcapitate stigma, easily detached from the ovary; ovary
glabrous, oblong in outline or clavate, blunt at apex, base narrowed,
immature fruits 1 cm long, thicker above the middle, prominently
punctate [of] lemon color, its [seeds have the] cotyledons folded, dark
green.…It is a form intermediate between M. tephrocarpum Turcz. [M. compressum] and M. pubescens Blm., but can be distinguished from either by its numerous, much smaller and glabrous mature leaves."
9. Micromelum diversifolium Miq. Ann. Mus. Bot. Lugd.-Bat. 1:211. 1863.
Type.—East Indian Archipelago, Moluccas, Halmahera Island (Teijsmann). Rijks Herb., Leiden.
Distribution.—Known only from the type locality.
Miquel's original diagnosis reads,
translated, as follows: "Twigs, petioles, and underside of the leaves,
as well as the inflorescence and the flowers, somewhat scurfy, slightly
tomentose-pubescent; leaves either with one pair of leaflets and an odd
one, thus trifoliolate, or unifoliolate leaflets, elliptic or
oblong-elliptic, obovate, acute or somewhat obtuse [at the tip], rounded
or slightly emarginate at the base, 7-8 spreading veins on both sides
[of the mid-rib]; flowers in short-terminal corymbs.
Leaflets 2-4.5 in. [5-11.5 cm long]; calyx with 5 short teeth; petals 5,
valvate, pubescent without; stamens 10, the alternate ones shorter,
anthers ovate-cordate; style distinct, stigma convex; berry ellipsoid,
somewhat stipitate-constricted at the base with 5 locules, with spirally
twisted [radial] walls."
Tanaka (1931b, p. 1), after having
examined type specimens of this species in Holland, both in the Rijks
Herbarium at Leiden and in the herbarium at the University of Utrecht,
stated: "This extremely interesting species is not known outside of the
Moluccas. The most remarkable features are the extreme
reduction of the number of the leaflets, the exceedingly villose floral
organs and the completely tomentose berry."
The origin of a species of Micromelum
found almost in the middle of the area of distribution of the genus,
differing radically from all the others in the great reduction of the
number of leaflets, is of much interest. The unifoliolate
form of the species (and of the variety mentioned below), has reached
the extreme reduction of the originally pinnate leaves to a single
leaflet that has occurred in species belonging to both the tribes of the
orange subfamily. Both tribes, however, still have species
with odd-pinnate leaves.
9a. Micromelum diversifolium var. cuneata Miq. Ann. Mus. Bot. Lugd.-Bat. 1:211. 1863.
Type.—The East Indies, Moluccas, Batjan Island (Teijsmann). Herb. Univ. Utrecht.
Distribution.—Moluccas: Batjan, Obi, and Halmahera islands.
Miquel’s original diagnosis reads,
translated, as follows: "With larger glabrous leaflets [than those of
the species], the terminal one acute or cuneate at the base; the lateral
leaflets somewhat acute at the base with 8-10 ribs on both sides."
Tanaka (1931b, p. 1), after examining the type specimen in Holland, wrote as follows: The "variety cuneata has
a deep cupulate calyx and the reduction of fuzziness is rather
noticeable; it has occasional unifoliolate leaves.
Additional material from Obi and Halmaheira [Halmahera] shows its fairly
uniform nature."
Subtribe 2. Clauseninae: Remote Citroid Fruit Trees
The subtribe Clauseninae contains three genera, Glycosmis, Clausena,and Murraya, having very simple, more or less primitive flower and fruit structures. The flowers of Glycosmis, Clausena,and Murraya are
usually borne in dense, often large, panicled clusters at the tips of
the branches. None of the genera of this subtribe have
spines. The leaflets are alternate on the rachis, which is
not articulated and does not break into segments when the leaves
fall. The flowers are 3- to 5-merous except that the stamens
(always free) are twice as many as the petals. The ovaries
have two to five locules and each locule contains one to two
ovules. The fruits are small berries, either soft and juicy
with few seeds immersed in mucilaginous pulp, or semidry with a clearly
distinguished, gland-dotted peel. The seeds are glabrous.
The three genera, Glycosmis, Clausena, and Murraya,
included in the subtribe range from India, Burma, and Indo-China to
Borneo, the Philippines, New Guinea, and Australia. Clausena also
has a wide distribution in tropical and subtropical Africa and in the
bush forests, at high altitudes, in the mountains of eastern and central
Africa. Three species and two varieties of Clausena are
known from Africa. Plotted on a globe, the distribution of
the Remote Citroid Fruit Trees is very similar to that of the
Near-Citrus Fruit Trees.
Glycosmis and Clausena show
very simple flower and fruit structures much like those found in some
genera of other subfamilies of the family Rutaceae (such as Amyris in the subfamily Toddalioideae). Close analogies to the flower and fruit structures shown by Glycosmis, Clausena, and also Murraya
can be found outside of the Rutaceae in the Simarubaceae and Meliaceae,
two plant families that stand very close to the Rutaceae in the natural
taxonomic system. The absence of oil glands in the leaves
and fruits is almost the only character that separates some of the
plants now classed in the Meliaceae from plants in the
Rutaceae. [A key to the genera of the subtribe Clauseninae is presented.]
The three genera of Remote Citroid Fruit Trees are clearly though distantly related to Citrus. Citrus has been grafted successfully on Clausena and Murraya and vice versa. Such grafts are often short-lived, but sometimes live many years. Grafts between Citrus and Glycosmis have not as yet been successful, but so far only a single species of Glycosmis has been tested, out of the large number known to exist. H. J. Toxopeus (1936, p. 6) made hybrids between Citrus and Murraya, but they were weak and remained stunted.
II. Glycosmis Corrêa
II. Glycosmis Corrêa, Ann. Mus. Hist. Nat. Paris 6:384. 1805. Sclerostylis Blume, Bijdr. Fl. Nederl. Indie 1:133. 1825. Chionotria Jack, Malay. Misc. 2(7):53. 1822; Dioxippe Roem. Syn. Hesper 1:33, 45. 1846; Myxospermum Roem. Syn. Hesper. 1:31, 40. 1846.
Type species.—Limonia pentaphylla Retz. (Obs. Bot. 5:24 [1789]) = Glycosmis pentaphylla (Retz.) Corr.
Distribution.—Southeastern Asia, East Indian Archipelago, Philippines, New Guinea, northeastern Australia.
Unarmed small trees or shrubs; new growth
covered with dense, usually ferruginous pubescence; leaves 1-foliolate,
3-foliolate, or odd-pinnate; leaflets with short petiolules, alternate,
long-lanceolate, more or less coriaceous; inflorescences compound,
often densely racemose; flowers small, 5-merous; sepals united to the
middle, with broad imbricate lobes; petals 5, white, long-elliptical or
oval, imbricate; stamens 10, filaments subulate, broadened below,
anthers small, often with oil glands on the back and tip; disk annular
or cylindric; ovary 2-5-locular, with 1 ovule in each locule; style very
short and thick, persistent, stigma simple or disk shaped; fruit a
juicy berry or dry; seeds oval, thick, with a membranaceous testa;
embryo with fleshy plano-convex cotyledons and a very short plumule.
This genus includes a large number of
very closely related thornless shrubs or small trees ranging from
southeastern Asia and the East Indies to northern Australia.
It will probably require careful study of living plants in the garden
and in the laboratory to tell whether or not the very numerous forms
that have been referred to this genus constitute good species or are
merely varieties. Some species are constant, others
variable. Five species have uniformly unifoliolate leaves;
two have regularly trifoliolate leaves; and several have leaves with
five leaflets; two or three species occasionally have as many as 13 to
15 leaflets. Most of the species have very small flowers,
but one (G. macrantha Merr.), native to Borneo, is said by Ridley to have very large flowers. Perhaps the most distinctive feature of Glycosmis is
the fact that the young twigs and leaves are densely covered with
closely-set, rusty-red pubescence, which does not seem to occur on any
other genus of Citrus relatives. The cotyledons of the seeds are thick and fleshy like those of Murraya, Clausena,and most of the other Citrus relatives, and differ widely from those of Micromelum, which are thin and folded.
Glycosmis citrifolia is sometimes
grown in greenhouses in this country, or even out of doors in the
southern states. The fruits are curious small berries having
translucent, slightly pinkish pulp, surrounding greenish-brown rounded
seeds, almost hemispherical when there are two seeds, but nearly
spherical if there is only one.
It is probable that, in addition to G. citrifolia,
other species are to be found in culture in European and American
greenhouses and gardens. Penzig (1887, pp. 194-209, Atl.
pls. 19-21) described and figured in detail the morphology and anatomy
of two forms of Glycosmis cultivated in Italy, one he determined as G. pentaphylla Corrêa, the other with less certainty as G. lanceolata Kurz.
In this latter species, Penzig found the plumule of the embryo, before
germination, to have abundant, rather long, slender, many-septate, brown
hairs with punctate walls. Such hairy plumules are
exceedingly rare and were not known to Penzig anywhere else except in
certain species belonging to the Meliaceae, a plant family closely
related to the Rutaceae.
The species of Glycosmis are still very inadequately described and need study more urgently than those of any other genus of the orange subfamily.
TENTATIVE LIST OF SPECIES OF GLYCOSMIS
The taxonomy of Glycosmis is in
such a state of confusion that it is not yet possible to key out all the
species or even to tell with certainty how many should be recognized as
valid.
Engler (1931, pp. 317-18) listed
twenty-one species as follows (numbers added and geographical names
modernized): (1) G. pentaphylla (Retz.) Corrêa (= G. cochinchinensis [Lour.]
Pierre), very widely distributed; leaves and inflorescences very
variable; leaves one- to two-paired or unifoliolate, with
long-lanceolate, blunt or acuminate leaflets; distributed in the whole
Indian Malayan region through the Malay Peninsula and Timor to northern
Australia, and north to the Philippines (among the many varieties is one
with a single lanceolate leaflet, in the Khasi Hills, Assam and Burma;
another [G. simplicifolia Spreng.] occurs in Java); (2) G. cyanocarpa
(Blume) Sprengel, common in the Malayan region and also found in the
eastern Himalayan region by Hooker fils and Thompson and sent out from
Kew as G. arborea; (3) G. macrocarpa Wight, leaves with 5-1 leaflets; in southern India and Perak; (4) G. ovoidea Pierre, leaves with 5-1 leaflets; in Cambodia; (5) G. erythrocarpa Hayata; leaves with 3-1 leaflets; in Taiwan; (6) G. montana Pierre (= Tetracronia cymosa Pierre, fide Tanaka), leaves with 13 leaflets; in South Vietnam (Cochin China); (7) G. tomentella Ridley, leaves with 15 to 7 leaflets; in Malay Peninsula, Selangor; (8) G. sapindoides Lindley, with a pubescent ovary; in Andamans, Malay Peninsula, Java; (9) G. malayana Ridley, leaves always 5-foliolate; abundant in Malay Peninsula from Singapore to Perak; (10) G. monticola Ridley, leaves always 5-foliolate; rare; in Malay Peninsula, Mt. Ophir, and Gunong Mering at 1,000 m altitude; (11) G. elata Ridley, leaves always 5-foliolate; rare; in Malay Peninsula (Kelantan and Kota Bharu); (12) G. mauritiana (Lam.) Tanaka (= Limonia mauritiana Lam. [Ency., 3:51, 1789] = Limonia pentaphylla Roxb. [Pl. Corom., p. 60, 1795] = G. triphylla Wt. [1833] = G. nitida Wt.
& Arn. [1834]), leaves with three or five leaflets, staminal
filaments flattened; along the Coromandel coast and in other parts of
India and Mauritius Island; (13) G. rupestris Ridley, leaves always trifoliolate; in Malay Peninsula; (14) G. puberula Lindley, leaves always trifoliolate; ovary pubescent; in Malay Peninsula.
The following species (nos. 15-18) all have unifoliolate leaves: (15) G. dinhensis Pierre, South Vietnam (Cochin China); (15a) G. bonii Guillaumin [= Murraya stenocarpa], North Vietnam, Tonkin; (15b) G. pseudoracemosa [Guill.] Swingle [= G. cyanocarpa (no. 2 above)], North Vietnam, Tonkin; (16) G. crassifolia Ridley, Malay Peninsula; (17) G. lindleyana Swing. nom. nov., G. macrophylla Lindley (non Miquel) ex Ridley [Fl. Malay Penin., 1:349
(1922)], leaves unifoliolate, thin, elliptical, acuminate, 8 by 3.5
inches; ovary conic, on a large disk; type, Wallich, No. 6377, Penang
local; (18) G. parkinsonii Tanaka, Burma, Tenasserim.
Tanaka (1930a, pp. 47-49) reported fifteen species in Indo-China and Thailand, among them: (19) G. pierrei Tanaka (= Thoreldora cochinchinensis Pierre), South Vietnam (Cochin China); (20) G. craibii Tanaka (= G. singuliflora Craib, non Kurz), Thailand; (21) G. longipes (Craib) Tanaka, Thailand. Ridley (1930, p. 79) reported one new species from Borneo (21a, G. oliveri Stapf [= G. macrantha Merr. (no. 29)]) with very large flowers. Engler includes these species in his list.
In addition to the foregoing list given by Engler (1931, pp. 317-18), Tanaka (1928b, 1930a, 1930b, 1931b, 1932e, 1937) has restored some old species and made a few new combinations and new species as follows: (22) G. esquirolii (Lév.) Tanaka, China, Kweichow Province; (23) G. parva Craib, Thailand; (24) G. winitii Craib, Thailand; (25) G. bilocularis Thwaites, Ceylon and peninsular India; (26) G. citrifolia (Willd.) Lindley, southern China, North Vietnam, South Vietnam, Laos, Cambodia, Thailand; (27) G. chlorosperma Blume, Java, Malay Peninsula; Borneo; Balabac Island, P.I.; (28) G. clemensii, Tanaka, North Borneo, Mt. Kinabalu; (29) G. macrantha Merrill, Borneo, Tawau; (30) G. angularis Elmer, Leyte Island, P.I.; (31) G. greenii Elmer, Philippines, Borneo, Moluccas, New Guinea, Australia; (32) G. platyphylla Merrill, Leyte and Samar islands, P.I.; (33) G. singuliflora Kurz, India, upper Assam; (34) G. macrophylla (Bl.) Miquel, Moluccas, Kei Islands; (35) G. boreana Narayanaswami, India, Assam.
Tanaka also transferred G. bonii (no. 15a above) to the genus Murraya (as a synonym of M. stenocarpa) and considered G. pseudoracemosa (no. 15b) to be a synonym of G. cyanocarpa (no. 2) and G. oliveri (no. 21a) a synonym of G. macrantha
(no. 29). This makes the tentative list total thirty-five
supposedly valid species. There are also many varieties both
old and new not listed here.
To show how many apparently good species
can be made out of a single species of the older authors, Kurz (1876,
pp.-33-40) made ten species that he thought good out of what had been
called G. pentaphylla (Retz.) Corrêa by Oliver (1861) and Hooker
(1875). Kurz described all ten and illustrated
seven. His key gives an excellent idea of the characters
shown by the species of Glycosmis; it is reproduced with slight emendations:
Of the foregoing ten species segregated by Kurz from G. pentaphylla (fig. 3-3), as understood by Oliver (1861) and Hooker (1875), four are listed by Kurz as having named varieties: (a) G. cyanocarpa and (d) G. trifoliata, each with four varieties; (e) G. triphylla and (h) G. arborea, each with two varieties in addition to the typical form. Seven of these segregates, a, b, c, e, f, g, h, of the key presented are figured in two plates.
Of these ten species, Kurz considered f, i, and k as distinct species "beyond any doubt," but was undecided whether d, e, and g should not be thrown "all into one species." In the preceding numbered list, six of Kurz's species are included: a = no. 2; c = no. 1; e = synonym of no. 12; f = no. 33; g = no. 14; k = no. 17. One species reduced to varietal rank by Kurz (var. beta of species a) was considered a good species by Engler (no. 8 above).
It is very necessary that all the species and varieties of Glycosmis be
subjected to a critical revision and then be fully described and
provided with a workable key. The descriptions of the older
species do not suffice to separate these species from the many new ones
now recognized, some of which are also inadequately described.
One or more illustrations of the following eleven species of Glycosmis are cited in Stapf (1929-1931, vol. 3, p. 298, and vol. 6, p. 554): G. arborea var. insularis Kurz; *G. cochinchinensis Pierre (no. 1); G. cyanocarpa Spreng. (no. 2); G. cymosa Kurz; G. lanceolata Spreng.; *G. madagascariensis Corrêa; G. montana Pierre (no. 6); G. pentaphylla Corrêa (no. 1), "(sub nomen Limonia pentaphylla)"; G. puberula Lindl. (no. 14); G. singuliflora Kurz (no. 33); *G. triphylla
Wight (no. 12). (The species names preceded by an asterisk
have colored illustrations and those followed by a number in parentheses
are thereby assigned to the species in the numbered list above.)
Glycosmis citrifolia (Willd.) Lindl. Trans. Hort. Soc. Lond. 6:72. 1826. Limonia citrifolia Willd. Enum. 448. 1809; L. parviflora Sims, Bot. Mag. pl. 2416. 1823; Glycosmis pentaphylla, var. beta, subvar. 2 (chinensis) Oliv. Jour. Linn Soc. Bot. 5(2):37. 1861. Illus. Sims, loc. cit. pl. 2416; Tillson & Bamford, Amer. Jour. Bot. 25:782, figs. 12, 13, 1938; Everett, Addisonia 21:pl. 687. 1940.
Type.—(Willdenow, No. 8116), Herb. Bot. Mus., Berlin-Dahlem.
Distribution.—Southern China, North Vietnam, South Vietnam, Cambodia, Laos, Thailand; widely cultivated in the Old and New Worlds.
Common name.—Chinese glycosmis.
A small tree or shrub with slender,
glabrous, greenish twigs with nodes 2-4 cm apart; leaves 1-, 2-, or
3-foliolate, rarely 4- or 5-foliolate; leaflets (or the single blade)
elliptical or oblong-elliptical, 6-17 X 2-5 cm, usually acute at the tip
and narrowly cuneate at the base, rarely somewhat rounded at base, more
rarely at tip, more or less covered with rusty-brown, short pubescence
when very young but soon glabrescent, lateral veins very numerous,
12-15, visible on both surfaces, variable in size, only the stronger
ones running nearly straight about 3/4 of the way to the margin, at an
angle of 50°-60° with the midrib; petioles 1.5-2.5 cm long, articulated
with the blade in simple leaves; petiolules of lateral leaflets 4-8 mm
long, with a channel on the upper side made by the decurrent leaf
margins, articulated only at the base with the rachis; the terminal
leaflet of pinnate leaves often articulated with a free portion of the
rachis 1-2 cm long; inflorescences small, axillary, usually 2-3,
sometimes 4-5 cm long, rarely terminal, sparingly branched, pedicels
very short, all parts of the inflorescence covered, when young, by a
dense rusty-brown pubescence; flowers small, white, 4-5-merous; sepal
lobes small, subtriangular, with more or less ciliate margins; corolla
campanulate, petals white, small, 3.5-4.5 mm long, bluntly cuneate at
the tips, soon falling; stamens 10, filaments filiform, slightly dilated
upward; ovary short, ovoid, 1.5-2 X 1.3-1.6 mm, rough or tubercular,
merging into a short, thick, persistent style, 0.4-0.5 mm long, tapering
upward and ending in a depressed cushion-shaped, persistent stigma, 0.5
mm wide and 0.2-0.3 mm high; fruits subglobose, translucent white or
pinkish, 11-13.5 mm diam.; seeds 1-3, oblong, cotyledons green.
This species, the Chinese glycosmis,
although widely cultivated in all tropical countries and in greenhouses
in the temperate zones, is still inadequately studied. The
description above was based on the type specimen (leaves only) preserved
at the Berlin-Dahlem herbarium, and on material from southern China
determined as this species by Tanaka. The Chinese glycosmis
is often labeled G. pentaphylla (Retz.) Corrêa in gardens or
herbaria, as many authors have considered it as being merely a form of
that species. It has also been called G. cochinchinensis Pierre
by some botanists. These three species, and all the others
for that matter, should be introduced into the United States and grown
side by side so that they can be properly distinguished, adequately
described, and tested as possible rootstocks for Citrus and as ornamental plants for greenhouse culture or for planting in subtropical gardens and parks. Glycosmis citrifolia has become naturalized in the hammocks of Key West, according to Small (1933, p. 759) and Everett (1940, p. 29).
III. Clausena Burm. f.
III. Clausena Burm. f. Fl. Ind. 87, 243. 1768. Cookia Sonner, 1782; Fagarastrum G. Don. 1832; Gallesioa Roem. 1846; Myaris Presl. 1849; Quinaria Lour. 1790; Piptostylis Dalz. 1851; Polcyema Voigt. 1845.
Type species.—Clausena excavata Burm. f.
Distribution.—Southwestern Asia,
East Indian Archipelago, Philippines, New Guinea, Australia,
northeastern tropical Africa from Abyssinia south to Natal and Pondoland
in Cape Province of the Republic of South Africa, central tropical
Africa, and western Africa from Angola to Sierra Leone.
Trees or shrubs without spines; leaves
odd-pinnate, leaflets alternate, usually 3-7 sometimes 19-32; rachis
usually not winged; inflorescences terminal or axillary, paniculate or
laxly racemose, flowers often in cymose clusters, flower buds small,
subglobose or short-oval or oblong, never long-cylindric; flowers small,
calyx 4-5 lobed; sepals fused into a cup below; petals free, 4 or 5
imbricate in the bud, usually elliptical; stamens 10, in 2 whorls, the
outer row opposite, the sepals usually longer, filaments more or less
dilated or flattened below, often geniculate where the filiform apical
portion joins the flattened and expanded basal portion, anthers ovate or
elliptical, rarely short and subglobose; gynophore well developed,
usually a perfectly glabrous hourglass-shaped column resting on an
annular nectary below and supporting (sometimes clasping) the base of
the ovary above; ovary with 2-5 locules, often pubescent or glandular,
ovules 2 in each locule (rarely 1); style deciduous, often shorter than
the ovary or equaling it in length (rarely longer), thick, sometimes
merging gradually into the ovary, often sharply delimited and narrowed
where it joins the ovary, stigma inconspicuous, sometimes subcapitate
after the style shrivels; fruits small, subglobose or ovate, with 2-5
segments, sometimes only 1 seed maturing; all flower parts usually
showing many (not all) cells strongly impregnated with tannin residues.
The most distinctive morphological character of the genus Clausena is
the gynophore, which in the typical species is a large, well-developed,
hourglass-shaped structure supporting the ovary. It is
perfectly glabrous and rests upon and merges into a short annular
nectary below and sometimes expands above into a thin-lipped cup-like
structure that encloses the base of the ovary. However, the
gynophore varies greatly in the different groups of species and in some
is so modified by expansions caused by development of oil glands that it
is difficult to recognize. Nevertheless, it is present in
all species of Clausena and separates them from the species of other related genera.
RELATIONSHIPS OF THE SPECIES OF CLAUSENA WITH ONE ANOTHER
The numerous species of this genus, still
only imperfectly studied with respect to the minute flower characters,
cannot be arranged now in natural sections or subgenera. It
is clear to any taxonomist who looks over carefully a large collection
of the species of Clausena that they can be classified into
obviously related groups, some small, some large.
Unfortunately, these groups are not clearly distinguished from one
another but, on the contrary, seem rather to merge into allied groups
without any sharp line of demarcation.
The study of the flower characters and in
particular of the gynoecium by means of serial microtome sections has
shown that important characters are found in the pistil that may help to
define the natural groups of species.
The type species of the genus, C. excavata,
has a striking hourglass-shaped gynophore which is completely
glabrous. It arises from the annular nectary below and,
after contracting, again expands and may even be slightly flaring where
it joins the ovary, which is strongly hirsute. The ovary,
which is 5-locular, merges into the style without any clear line of
demarcation, and the style is not narrowed where it joins the tip of the
ovary.
On the other hand, in C. indica
the style is abruptly contracted and countersunk into a conical
depression at the tip of the ovary, which has two to five
locules. This species was made the type of the genus Piptostylis and belongs to a large group which includes many other species.
The species C. pentaphylla at
present prevents a clear separation of the two groups outlined
above. The pistil shows no sharp boundaries of gynophore,
ovary, and style; the gynophore is as broad as the ovary—not
hourglass-shaped—and is more or less lobed, often having short processes
each ending in an oil gland. The style may be slightly
contracted where it joins the top of the ovary but is frequently more or
less swollen with oil glands just at this junction.
Clausena lansium
stands apart from all the other species of the genus in having a
star-shaped bud (due to its five strongly carinate petals) and a
5-angled ovary, corresponding in position to the five petal keels in a
cross section of the bud. The pistil is unusually large; the
ovary is very strongly hirsute and merges into the style, which is
slightly contracted at the base. It is hourglass-shaped as
in C. excavata. Furthermore, the twigs show a central
gum canal, doubtless formed by a lysigenous breakdown of the
tissues. The locules of the ovary contain scattered but
well-developed hairs which arise on the dorsal and outer portion of the
lateral walls and usually grow more or less toward the axis of the
ovary. One much longer hair arises at the base of each
locule and grows vertically upward, nearly to the top of the locular
cavity (Penzig, 1887, p. 179, pl. 16, figs. 11, 12, 16). The
fruits are apparently the largest in the genus and the locules of the
ripe fruits are almost filled with a pulpy tissue which Penzig found to
arise from the hypertrophy and multiplication of layers of cells nearest
to the endocarp. This species was the type of the genus Cookia, but no other species having similar characters are yet known.
Clausena lenis also
stands alone in the genus, having leathery petals and a most peculiar
gynophore, no longer hourglass-shaped as in almost all the other
species. Just above the thin annular nectary there is a
narrow constriction followed by a cylindrical gynophore evidently
swollen by a ring of 12 to 15 oil glands at its very base; it merges
above into the ovary. The style is slender, two to three
times as long as the ovary, by far the longest of any species in the
genus, and contracted below, where it joins the ovary. The
leaflets are subdentate, and the largest ones are lateral leaflets
attached about two-thirds of the way up the rachis.
Clausena guillauminii has leaves
showing dimorphic oil glands, the larger ones being 1/3 to 1/2 mm in
diameter, and deep red by transmitted light; the flower
parts show a single large oil gland at the tip of each sepal, each
petal, each anther, and each locule of the ovary. C. wallichii has almost the same distribution of the oil glands in the flower parts. C. papuana
shows great variation in the size of the oil glands in the leaflets and
has the oil glands similarly distributed in the flower
parts. These species may be closely related; certainly C. guillauminii, C. wallichii and C. luxurians are. The last-named species have the rachis slightly winged, unlike all other species of Clausena.
THE SPECIES PROBLEM IN CLAUSENA
Of the twenty-three species of Clausena
recognized here, ten were published from 1900 to 1930 and one as late
as 1940. Of the others, one was published in 1892 and eleven
from 1768 to 1875. It now appears that many of the older
species, although they were described adequately enough to distinguish
them from the other species known at the time, were nevertheless not
described fully enough to separate them clearly from the many species
recently discovered. Then, too, the range of the older
species has been extended steadily as new botanical collections have
been made. Very widely distributed species like C. excavata and C. anisata show, as might be expected, very many variations in their characters in specimens collected from widely different localities.
For these reasons a clear-cut definition of the species of Clausena will require a great amount of work which can be done only by using all the material in the leading herbaria of the world.
Tanaka, who assiduously studied Clausena (and
also the other genera of Aurantioideae) from 1927 to 1937 in the
herbaria of Europe, Asia, and America, has done much to clarify the
species of this genus. He has published notes on them in all
his valuable papers included in the series "Reviso aurantiacearum."
Swingle was permitted to borrow nearly a thousand sheets of material of Clausena from many of the leading herbaria of the Old World and the New, including all the Clausena
material in the herbariums of the Royal Botanic Gardens at Kew and the
Royal Botanic Garden at Calcutta. Thanks to these loans he
was able to make a close study of many of the actual type specimens of
the species of Clausena. In the study of this rich
material he used a modification of Juel's method of softening herbarium
material, after which it was fixed, dehydrated, imbedded, cut into
serial microtome sections, double-stained, and finally mounted
permanently on glass slides (Swingle, 1939b, p. 270).
In this work, Swingle had the skillful assistance of Dr. Albert H. Tillson. Figure 3-4, which shows longitudinal microtome sections of nine species of Clausena,
makes clear how helpful this method is in studying herbarium material,
especially the pistil just after the petals and stamens have
fallen. It has not, however, been possible to work out all
the species satisfactorily. Some species, like C. anisata,
vary so greatly that months of work should be needed to study its
numerous forms adequately, and other species are not well enough
represented in herbaria for any complete study.
GEOGRAPHICAL DISTRIBUTION AND USES
The geographical distribution of Clausena
is of interest since it has the widest range of any genus included in
the orange subfamily, species being found all the way from northwestern
India to China and Taiwan, south through the East Indian Archipelago to
Timor, northern Australia, and New Guinea. Moreover, there
is a group of three species that covers a wide range in Africa, from
Ethiopia (Abyssinia) to Cape Province and through western Africa from
Angola north to Sierra Leone.
There are wide differences in the
character of the growth and the height of the species; they range all
the way from shrubs 20 to 40 cm high in Indo-China to trees reaching a
height of 20 m (66 feet) in Africa.
Several species of Clausena produce edible fruits, but up to now only one of them, the Chinese wampee, C. lansium,
is cultivated (in southeastern China) on a commercial scale, with many
varieties, the fruits varying greatly in size, flavor, and time of
ripening. One other species, the Indian wampee, C. dentata var. dulcis,
is gathered on a large scale from wild trees in the state of Madras in
southern India, where it is a highly appreciated fruit, said by the
British experts who have studied it to be of excellent
flavor. At least two other forms are said to produce edible
fruits, C. indica of India and Ceylon and C. dentata var. henryi of southwestern China.
The Chinese wampee, C. lansium, can be used as a rootstock for Citrus, provided a few twigs of the wampee are left growing below the graft. Other species of Clausena should be tested as stocks for Citrus and also for the edible-fruited species of Clausena.
Clausena anisum-olens, a species
common in the Philippines from Luzon Island to Mindanao Island, grows in
the forests from sea level to 1,500 m altitude. It is a
small tree 3 to 6 m tall and has leaves with a strong odor of anis
oil. West and Brown (1920, pp. 211-12) stated that the
suggestion had been made that the leaves could be used locally in
preparing anisado, a favorite alcoholic beverage among the
Filipinos. The essential oil of the leaves was found by
Brooks (1911, p. 344) to consist very largely (from 90 to 95 per cent)
of methyl chavicol, which is easily converted into anethol, the true
anis oil. The leaves yield about 1.2 per cent of oil after
five hours’ distillation over steam. This essential oil is
not known to occur in such a large proportion in any other plant of the
family Rutaceae.
It is highly probable that other species
of this large and very widely distributed genus, when studied carefully,
will be found to be of value for their fruits, for use as rootstocks,
for their essential oils, or for planting as ornamentals because of
their abundant white flowers and handsome foliage.
The following four keys covering the species native to the four principal regions where Clausena is indigenous will help in giving an idea of the differences between the species.
1. Clausena excavata Burm. f. Fl. Ind. 87. 1768. Murraya burmanni Spreng. 1825; Amyris sumatrana Roxb. 1832; A. punctata Roxb. 1832; Gallesioa graveolens Roem. 1846; Clausena lunulata Hay. 1911; C. tetramera Hay. 1916; C. moningerae Merr. 1923. Illus. Burmann f. loc. cit. pl. 29, fig. 2; Guillaumin, in Lecomte, Fl. Gén. Indo-Chine 1:664, fig. 70(8-10). 1911; Tillson & Bamford, Amer. Jour. Bot. 25:782, fig. 15. 1938; fig. 3-4,A-B, and fig. 3-5 this work.
Type.—Java (Burmann, Dauhon Kongeere, No. 29). Herb. Van Royen, in Rijks Herb., Leiden, sheet "908, 203-…1051" (fide Tanaka, 1932e, p. 422).
Distribution.—India: Coromandel
and northern districts to Bhutan; Burma; Thailand; southern China; North
Vietnam; South Vietnam; Laos; Cambodia; Malay Peninsula; Sumatra; Java;
Borneo; Philippines; New Guinea.
Hooker (1875 vol. 1, p. 504) described
this species, with slight rearrangement, as follows: "A [small] tree,
branchlets as thick as a crow-quill and, as well as the inflorescence
and leaflets, more or less softly tomentose; leaves 15-30 foliolate,
6-12 in. [15-30 cm] long; petiole slender, cylindric, more tomentose
than the leaflets, which are very oblique at the base, petioluled, 2-3.5
in. [5-8 cm] long, ovate or lanceolate, acuminate, membranous, crenate,
upper ones often falcate. Panicle 4-12 in. [10-30 cm] high,
pyramidal, branches spreading, alternate. Flowers 4-merous,
shortly pediceled, 1/6 in. [4 mm] diam., white, buds
globose. Petals oblong, glabrous. Ovary ovoid or
elliptic, sub-4-gonal stipitate, hairy or hirsute; style stout, about
equaling the ovary. Fruit 3/4 in. [18 mm] diam., broadly
oblong."
Burmann’s original description of C. excavata
(l.c.) covers the stamens, in translation, as follows: "Staminal
filaments 8, subulate, shorter than the corolla, the inferior part
dilated and thickened, hollowed out (‘excavata')2 within."
Guillaumin (1911, p. 661) described the
stamens, in translation, as follows: "Stamens 8, one-third or a half
shorter than the petals; filaments awl-shaped above, then suddenly
dilated, concave and papillose at the base with a hump at the upper
part; anthers oval, apiculate." He also figured the
stamens (1911, p. 664, fig. 70 [9-10]), showing the lower expanded and
papillose part of the filament to be strongly curved outward and the
upper slender, smooth portion to be even more strongly curved outward,
almost into a semicircle.
The gynoecium of this species, as studied
from serial microtome sections, shows the following structure: pistil
3.2-4.2 mm long; gynophore very strongly developed, completely glabrous,
hourglass-shaped, usually with a basal annulus 1-1.2 mm diam., then
contracted to 0.7-0.8- mm diam., then expanded into a more or less
cupulate top, 1-1.2 mm diam., embracing the base of the ovary, with
edges often showing small oil glands; ovary cylindrical or conoid,
usually strongly hirsute, 1-5 mm long, 1-1.2 mm wide, often with a few
small oil glands where the style is attached; style cylindrical, not
narrowed at point of attachment, but merging into the top of the ovary,
glabrous, 1-1.2 mm long, 0.5-0.8 mm wide, stigma very short,
flat-topped, only slightly wider than the style. (fig. 3-4,A-B.)
This species is the type of the genus Clausena
and has the widest distribution of any species, ranging through the
East Indian Archipelago to southeastern Asia. As would be
expected from its very wide range, the species has undergone many
variations, until the forms from Sumatra and Taiwan do not at first
sight seem to belong together in a single species. However,
the pistil of this species is distinctive, and is much the same in all
these forms and very different from that of the other species of the
genus Clausena. It has a rather full, smooth,
hourglass-shaped gynophore supporting the more or less strongly hirsute
ovary. The ovary tapers gradually into the thick style,
which shows no constriction at its base as do the styles of many other
species.
Only one variety is here recognized, but
it would be easy to designate three or four equally well characterized!
1a. Clausena excavata var. villosa Hook. f. Fl. Brit. Ind. 1:505. 1875.
Type.—Burma, Rangoon (McLelland, No. 1854). Herb. Kew.
Distribution.—Upper Burma; also Thailand, Indo-China, Malaya, and rarely in Nepal (fide Tanaka, 1937, p. 231).
Whole plant clothed with soft spreading hair: petals hirsute.
This hairy form is found near the northcentral part of the range of the species.
2. Clausena lansium (Lour.) Skeels, U.S. Dept. Agri. Bur. Pl. Ind. Bul. 168:3. 1909. Cookia punctata Sonner. Voy. Ind. Or. 2:231. 1782; Quinaria lansium Lour. 1790; Cookia wampi Blanco, Fl. Filip. ed. 1. 358. 1837; Clausena wampi Oliv. Jour. Linn. Soc. Bot. 5(2):34. 1861. Illus. Sonnerat, loc. cit. pls.
130, 139; Jacquin, Pl. Rar. 1:pl. 101 (col.). 1797; Penzig, Studi Bot.
Sugli Agrumi, Atl. pls. 15, 16. 1887; De Wildeman, Icon. Sel. Hort.
Then. 6:pl. 226. 1908; Mill Tsen, Yuan I, Hort. 2:596-97. 1936, 2 text cuts with 6 figs. of fruits and 6 of leaflets; fig. 3-4,E,F,I, and fig. 3-6 this work.
Type.—China, Canton (Loureiro). Herb. Mus. Hist. Nat., Paris.
Distribution.—Native in southern China and Indo-China; widely cultivated in tropical and subtropical regions.
Common name.—Wampee.
Oliver (1861, p. 34) gave a Latin
diagnosis of this species that, translated, reads as follows: "Tree or
shrub; branches at first pubescent or puberulous; leaves
5-7-9-foliolate, 20-25 cm long; leaflets ovate-elliptic, lanceolate or
ovate, with petiolules 2-6 mm, more or less oblique at the base, apex
obtuse or subemarginate, sometimes almost mucronulate, slightly
acuminate, margin undulate-crenate or slightly serrulate, becoming
glabrous or glabrescent, the midrib and veins often sparsely scabrous,
glabrescent below; terminal leaflet often 6-10 cm long; flowers
subsessile or shortly pedicellate, in many-flowered cymose panicles;
calyx-5- (rarely 4-) merous, lobes triangular or ovate; stamens 10,
alternate ones shorter, filaments dilated above the middle, flattened,
subulate above, anthers oblong or elliptic, cordate-sagittate at base,
with a dorsal gland; ovary shortly stipitate, glandular, very often
5-locular, ovules in pairs [in each locule], superposed, the upper one
peltate on the side or toward the base, the lower one subpendulous;
style very short, distinct, glabrous above, stigma 5-lobed, slightly
wider than style; fruit usually with 5 locules, 5-seeded, or by abortion
1-seeded, or sterile, ovoid-globose, pubescent, 1 in. [25 mm] or less
diam.; cotyledons fleshy, equal."
This species differs widely from all the other species of the genus, as has been noted.
The wampee is a highly esteemed fruit tree in southern China, where
sour, subacid, and sweet varieties are known. The white or
yellow fruits are ovoid or subglobose, about the size of a pigeon’s egg,
but varying in size and shape with the variety cultivated.
The inflorescences are large panicles at the ends of the branches, so
the fruits occur in rather openly-spaced clusters. In
texture, the wampee fruit is much like a loquat and is a berry without a
tough peel. An illustrated treatise in Chinese by Mill Tsen
[Ts’êng Mien-chih, in Mandarin transliteration] (1936) described in
detail six varieties and figured the fruit and a leaflet of each
variety. (Mill Tsen mentioned another variety [no. 6 below],
which is not figured.) Table 3-1
shows the principal characters of the fruits of these Foochow varieties
(the leaves vary almost as much as the fruits but are omitted from the
table).
According to Mill Tsen, Professor Wên
Wên-kuang of Sun Yat-sen University at Canton, China, listed eight
varieties of the wampee grown in Kwangtung Province. These
varieties are not described in detail but are given long descriptive
names such as "white-hairy-chicken-heart-sweet-wampee";
"long-chicken-heart-sour-wampee";
"yellow-hairy-chicken-heart-sour-wampee," etc.
Although the wampee is only remotely related to Citrus, it can be grafted on a Citrus
rootstock, and is thereby forced into early flowering and
fruiting. The rough lemon can be grafted on the wampee and
will grow for many years if a small branch of the wampee is allowed to
grow just below the graft. Any desired Citrus fruit
can be top-grafted on the rough lemon and may live for many years and
may even be made to fruit. However, the graft union of the
rough lemon on the wampee is poor and badly overgrown.
Wampee on Citrus seems to make a much better and more permanent union.
3. Clausena pentaphylla (Roxb.) DC. Prodr. 1:538. 1824. Amyris pentaphylla Roxb. Fl. Ind. 2:247. 1832. Illus. fig. 3-4,C.
Type.—British India, United
Provinces, Cawnpore, a living plant sent to Calcutta Bot. Gard. and
grown there (Roxburgh). Herb. Brit. Mus., London.
Distribution.—India: western Himalayan region, from Garhwal to Sikkim, northern Uttar Pradesh and Oudh.
Brandis (1906, p. 114) gave a condensed
description of the species as follows: "A strongly aromatic shrub, young
shoots and inflorescences silky-tomentose, full-grown leaves
pubescent. Leaflets 5 or 7, nearly opposite, 4-6 in. [10-15
cm] long, secondary nerves prominent beneath. Flowers
yellowish, in terminal panicles. Berry verrucose, pale
orange, 1/3-1/2 in. [8-13 mm] long." Duthie (1905, p. 138)
in his Flora of the Upper Ganghetic Plain, a region where this is the only native species of Clausena,
described it as follows: "A deciduous shrub; young parts
silky-tomentose. Leaves large, 3-7-foliolate.
Leaflets subopposite or alternate, 2-6 in. [5-15 cm] long, ovate or
lanceolate, acuminate, entire, shortly stalked, softly tomentose
beneath; main lateral nerves prominent. Flowers 4-merous,
1/4 in. [6 mm] across, yellowish, in erect terminal downy
panicles. Sepals triangular, acute. Petals
oblong, concave. Filaments short, broad. Berry
1/2 in. [13 mm] diam., ovoid, papillose, pale orange."
Good flowering material collected by J.
F. Duthie in the western Himalayan region at Gonda Dun (No. 21613, Herb.
Arnold Arbor.) shows the following gynoecium characters: The pistil,
2-2.2 mm long, shows no sharp boundaries of disk, ovary, style, and
stigma. The 3- or 4-locular ovary is 1-1.2 mm wide and 0.9-1
mm long, irregularly tuberculate and sparingly pilose; the style is
cylindrical above, 0.35-0.45 mm wide, with no obvious stigma; below, it
may be slightly contracted where it joins the top of the ovary, but very
often it is swollen with rather large oil glands at or just above its
junction with the tip of the ovary and in consequence may be nearly as
wide as the ovary. The disk is most irregular, usually as
broad as the ovary but more or less lobed and even having short
processes each ending in an oil gland. The locules of the
ovary run deeply into the disk, which in longitudinal section is not
clearly separated from the base of the ovary.
This species, remarkable for its
deciduous foliage and shrubby habit, has even more remarkable pistils
that depart widely in their characters from those of all other species
of the genus. Its nearest analogue in gynophore morphology
is the anomalous C. lenis, which has a more or less syncopated gynoecium.
4. Clausena indica (Dalz.) Oliv. Jour. Linn. Soc. Bot. 5(2):36. 1861. Piptostylis indica Dalz. Hook. Jour. Bot. & Kew Gard. Misc. 3:33. 1851; Bergera nitida Thw. Enum. Pl. Zeyl. 46. 1858. Illus. Dalzell, loc. cit. pl. 2; Engler, Die Nat. Pflanzenfam. 3(4):187, fig. 108,L-O. 1896; ibid. ed. 2. 19a:321, fig. 146,L-O. 1931; Talbot, Forest Fl. Bomb. Presid. 1:195, fig. 119. 1909; fig. 3-4,K this work.
Type.—British India, Bombay Ghats, Kanara (Dalzell). Herb. Kew.
Distribution.—India: western peninsula, Bombay Ghats to Anaimalai Hills, Madras State, eastern coast, Tranquebar; Ceylon.
Hooker (1875, vol. 1, p. 505) gave a
description that may be summarized as follows: "A glabrous shrub or
small tree; leaves 9-11-foliolate, 4-10 in. [10-25 cm] long; petioles
slender…glabrous or puberulous; leaflets polymorphous, very oblique
oblong-ovate, elliptic or lanceolate, rarely almost rounded, tip
rounded-obtuse and notched or acute or acuminate, margins crenulate,
very dark with raised glands on both sides when dry; inflorescence a
peduncled panicle, corymbosely branched above; flowers 1/6 in. [4 mm]
diam., very shortly pediceled; ovary 2-5 celled, glabrous, papillose;
ovules 2 in each cell; fruit 1/2 in. [13 mm] diam., globose, yellow,
edible." Talbot (1909) added a few details that can be
condensed as follows: Leaflets subcoriaceous, 2-4 X 1-2 in. [5-10 X
2.5-5 cm]; petiolules 1/4 in. [6 mm] long; petals broadly ovate; stamens
with filaments broad, as long or longer than the versatile anthers;
ovary usually 3-loculed; fruit pulpy, edible. Dalzell (l.c.)
described and figured the style as much shorter than the ovary, thick,
cylindrical, with the stigma scarcely wider than the style, which is not
expanded at the base where it is situated in a depression at the tip of
the ovary and wholly caducous. He described the flowers as
4- or 5-merous but did not see any but 3-locular ovaries.
Clausena indica is a shrub or
small tree, 2 to 2.3 m high, common in the evergreen rain forests of the
Ghats of western peninsular India. In spite of its rather
limited distribution, it shows great variation in the shape of the
leaflets which differ greatly in outline, being "very oblique" in
Ceylon, according to Trimen (1893, p. 221), but only slightly if at all
oblique at the base in the type locality in the Bombay Ghats, as is
shown by Dalzell's careful drawing (and even more by his type specimen
in the Kew herbarium) as well as by Talbot's sketch. The
ovary varies even more strikingly than the leaflets, having regularly
three locules in the type locality, according to Dalzell (l. c.) and Talbot (1909), whereas in Ceylon it always has two locules, fide Dalzell (l. c.)
and Trimen (1893, p. 221). A specimen from Ceylon sent by
the Royal Botanic Garden at Peradeniya to the herbarium of the Arnold
Arboretum (Tanaka's "Det. A-229") has 2-, 3-, and 4-locular ovaries in
the same inflorescence. Oliver and Hooker both found forms
with 4- or 5-locular ovaries.
As this species bears edible fruits, it
should be hybridized, if possible, with the Chinese wampee and with
other species that yield edible fruits.
5. Clausena heptaphylla (Roxb.) Wt. & Arn. Prodr. 96. 1834; and in Wall. Cat. 8508. 1848. Amyris heptaphylla Roxb. Fl. Ind. 2:248. 1832; Clausena forbesii Engl. 1896. Illus. Guillaumin, in Lecomte, Fl. Gén. Indo-Chine 1:664, fig. 70(11-12). 1911; Tillson & Bamford, Amer. Jour. Bot. 25:782, fig. 14. 1938; fig. 3-4,D this work.
Type.—British India, "about Calcutta" (Roxburgh). Herb. Brit. Mus., London.
Distribution.—India, Burma, Thailand, North Vietnam, South Vietnam, Laos, Cambodia and Sumatra (also Java, fide Tanaka).
The description of this species given by
Guillaumin (1911, p. 662) reads, translated, as follows: "A shrub;
leaves 30-50 cm long; leaflets 7-11, unequal-sided at base (except the
terminal one), membranaceous, rigid, long-oval or lanceolate, 4.5-16 X
2.5-7 cm, acute at base, acuminate at apex, entire, glabrous except the
midrib on the under surface, with 6-7 pairs of lateral veins which are
raised on the under surface; petioles cylindrical, with very short
pubescence, glandular. Inflorescences terminal, paniculate,
pyramidal, shorter than the leaves, with alternate, slightly and shortly
pubescent branches; pedicels very short with 2 basal, shortly pubescent
bracts articulated at the very base. Sepals 4, triangular, 1
mm long with ciliate margins. Petals 4, obovate, glabrous
but papillose, twice as long as the sepals. Stamens 10,
slightly shorter than the petals; filaments filiform at base then
abruptly dilated below the anther; anthers attached dorsally along the
middle, almost rhombohedral, without horns. Disk very short,
glabrous. Ovary cylindric, quadrangular glabrous, as long
as the stamens, 4-locular, each with 2 superimposed ovules; style
cylindrical, as long as the ovary. Fruit ovoid, 2 X 1 cm,
very glandular, with 1 or 2 seeds."
Hooker (1875, vol. 1, p. 504), who
described the species from material from a wide range of localities,
noted that it is a "branching bush, smelling strongly of aniseed.…Leaves
6-16 in. [15-40 cm long]…leaflets sometimes 8 in. [20 cm
long]…membranous, ovate or lanceolate, acuminate, very obscurely
crenulate, pale beneath, nerves and costa slender.…Flowers 1/6 in. [6
mm] diam., pedicels slender, buds glabrous, yellow-white.…Berry 1/2 in.
[12 mm] long, oblong, white-reddish or pale yellow, glandular."
Engler (1931, p. 321) mentioned in his notes on Clausena: "C. forbesii [from
Sumatra] with leaves nearly one meter long, having eight paired
leaflets," the longest leaves yet reported in the genus.
Probably it is merely an unusually vigorous growing form of this
polymorphic species.
This species, in spite of its abundance,
needs renewed study to determine its limits of distribution in the East
Indian Archipelago. Tanaka (1937, p. 231) even reported it
from the Sunda Islands and Timor. It has not been reported
from Ceylon or from Borneo or the Philippines.
5a. Clausena heptaphylla var. engleri (Tan.) Swing. Jour. Wash. Acad. Sci. 32:26. 1942. Clausena engleri Tan. Med. Rijks Herb. Leiden 69:6. 1931; (?) C. platyphylla Merr. Pap. Mich. Acad. Sci. 23:182. 1938.
Type.—Sumatra (Lörzing, No. 6825). Rijks Herb., Leiden.
Distribution.—Known only from Sumatra.
Tanaka's original description reads,
translated, as follows: "A robust plant; rachis of leaf 36 cm long,
7-foliolate; leaflets ovate, acuminate-caudate, pointed at the base,
with conspicuous veins, when dry chartaceous, very green on the upper
surface, pallid below, margins serrate, veins rufescent, with very short
petiolules, entirely glabrous. Inflorescence terminal, 28
cm long, branched into many-flowered panicles. Flowers
small, 5-merous, short-pedicellate. Calyx thin, scutellate,
with triangular pilose lobes having ciliate margins. Petals
5, caducous. Stamens 10, filaments dilated, anthers
large. Ovary cylindrical, pilose; style linear, straight or
curved, stigma somewhat capitate."
Tanaka, in his remarks following the
Latin description, stated that this plant resembles the robust form of C. heptaphylla,
but the latter has 4-merous flowers, glabrous ovary, and entire
leaflets." The photograph of Tanaka's type specimen shows it
to have large leaflets, 11 to 19 by 5 to 8 cm, at the apex, cuneate and
only slightly unequal-sided at the base, with 10 to 12 pairs of lateral
veins. C. platyphylla, recently described as a new species from Asahan in northeastern Sumatra, seems likely to prove to be a synonym of C. heptaphylla var. engleri
once a comparative study is made of the type specimens of these two
plants. Both of them have leaflets of about the same size,
of similar shape, with the same number of lateral veins, and even share
the peculiarity of the dried leaves being dark, shining green above and
much lighter, pallid green below. The ovary of var. engleri is pilose, whereas that of C. platyphylla shows scattered pubescence; the ovary of the species C. heptaphylla is glabrous.
6. Clausena dentata (Willd.) Roem. Syn. Hesper. 44. 1846. Amyris dentata Willd. Sp. Pl. 2:337. 1799, Clausena willdenowii Wt. & Arn. 1834. Illus. Wight, Icon. Pl. Ind. Or. 1:pl. 14/339. 1838; Beddome, Fl. Sylv. Anal. Gen. pl. 7. 1871.
Type.—British India (Willdenow, No. 7293). Herb. Bot. Mus., Berlin-Dahlem.
Distribution.—Ceylon; India: western peninsula, eastern Himalayan region, Sikkim to northwestern Burma; Thailand; southwestern China.
This species was described by Hooker fils
(1875, vol. 1, p. 506), with some transpositions, as follows: "A large
shrub, glabrous or…pubescent; branchlets slender. Leaves
5-13-foliolate, 6-16 in. [15-40 cm] long; petiole slender, terete;
leaflets 1-2 in. [2.5-5 cm] long, oblique, oblong-ovate or
ovate-lanceolate, obtuse, acute or obtusely caudate-acuminate,
crenulate, membranous. Racemes slender, axillary, 3-10 in.
[7.5-25 cm] long, branches or pedicels divaricating. Flowers
fragrant, usually 4-merous, 1/3 in. [8 mm] diam., whitish; buds
globose. Petals oblong, concave, glandular, ovary stipitate,
4-angled or grooved, glabrous, ovules 2, superimposed in each cell;
style short, thick. Fruit globose, from the size of a pea to
a cherry, whitish-green, pellucid."
A specimen from southern India, Madras
State, Hosur Taluk (coll. by Mrs. Kanoth Yeshoda; now in Herb. Arnold
Arbor.), shows the restored flowers in serial microtome sections to have
the following characters: pistil, 3.5 mm long; gynophore short, 0.5-0.6
mm long, narrowed to 0.7 mm just below the flatly rounded, nearly
truncate ovary base; ovary subglobose, 1.3-1.4 mm long, 1.2-1.3 mm wide,
tip abruptly rounded with a slight depression in which the nearly
cylindrical style is attached; style 1.5 mm long, 0.3-0.4 mm wide,
stigma short, cushion-like, 0.5 mm wide. Cross sections show
4-locular ovary with a very short process at the tip of each locule but
with no large oil gland. The pedicels of the flowers are
unusually long (4-6 mm) and slender, with small bracts at the base.
This species, like C. suffruticosa and the three African species, C. abyssinica, C. anisata, and C. inaequalis,
has axillary flower clusters, not terminal panicles as in most of the
other species. The long pedicels of the flowers are unusual
in Clausena.
6a. Clausena dentata var. pubescens (Wt. & Arn.) Tan. Jour. Bot. Brit & For. 68:227. 1930. Clausena pubescens Wt. & Arn. Prodr. 1: 96. 1834; C. willdenowii var. pubescens (Wt. & Arn.) Hook. f. Fl. Brit. Ind. 1:506. 1875.
Type.—Ceylon (Wight, No. 328b). Herb. Glasgow Univ.
Distribution.—Ceylon; India: Mysore State.
Tanaka (1930b, p. 227) described
this variety, in translation, as follows: "Leaves, inflorescences, and
petioles densely villose. Fruits globose, rather small."
Tanaka (1937, p. 230) stated that this variety is very rare in Mysore and Ceylon.
6b. Clausena dentata var. longipes (Craib) Tan. Bul. Soc. Bot. France 75:709. 1928. Clausena longipes Craib, Kew. Bul. Misc. Inform. 1926:340. 1926.
Type.—Mê Lan, Mê Hawng Sawa, Thailand, 700 m altitude, on limestone rock (Kerr, No. 5486-A). Herb. Kew.
Distribution.—Thailand and upper Burma.
Differs from the species in having (1)
very slender, few-flowered inflorescences ending in long, slender
pedicels, 5-15 X 0.2-0.3 mm; (2) slender (1.7-2-5 X 1 mm) ovaries that
merge gradually into the rather long style (2.5-3 X 0.6-0.7 mm); (3) no
oil gland at the tip of each of the 4 locules of the ovary; (4) very
narrow radial locule walls, not swollen where they cross to make an
axial pillar; and (5) few tannin cells in the periphery of the ovary and
none in the axis.
This variety appears at first sight to be specifically distinct from C. dentata,
but some of the material of the species from southern India shows very
slender inflorescences and almost equal-sided leaflets very like those
of var. longipes. Craib (1926, p. 234) considered this plant to be related to C. dentata and to C. suffruticosa.
6c. Clausena dentata var. dulcis (Bedd.) Swing. Jour. Wash. Acad. Sci. 28:532. 1938. Cookia dulcis Bedd. Madras Jour. Lit. Sci. 2 ser. 22:73. 1861. Clausena willdenowii var. dulcis Bedd. Fl. Sylv. 44. 1871.
Type.—British India, Madras Presidency, Anaimalai Hills (Beddome). Herb. Kew.
Distribution.—India: Anaimalai Hills south to Travancore.
Common name.—Indian wampee.
Beddome (1861, p. 73) described his new
species in general terms as follows: "A tree with a delicious fruit not
uncommon on the Anamallays up to 3,000 feet both in the moist woods and
in the drier forests—it flowers in April and the fruit begins to ripen
at the end of June—the fruit is more grateful to the taste than that of
the Whampee (Cookia punctata). The tree is well known
to the hill tribes and called 'Mor Koorangee.’ I have often
met Kaders carrying home on their backs basket loads of this and the
fruit of Pierardia sapida, which is also abundant in these
jungles." He also noted that the "fruits are globose, size
of a large cherry." Beddome in a later publication (1871, p.
44) stated: "This is a tree 30 feet high, with a trunk several feet in
girth, bearing a very delicious fruit as large as a large cherry, as
succulent as a grape, and somewhat of the flavour of the black
current…it is abundant about Toonacodava (elevation 2,000-3,000 ft.),
both in the moist and dry forests, and is in fruit from June till
August; specimens in flower were sent to Prof. Oliver, who pronounces it
only a form of [Clausena] Willdenowii [= C. dentata], so I will not attempt to separate it, but I believe it quite a distinct species…in comparison with true C. Willdenowii it has leaves that are more membranaceous, highly odoriferous, more prominently dotted, and very erose toward the apex."
This variety is not as yet clearly
distinguished from the species, and most taxonomists have not recognized
it as valid. It should be noted, however, that
investigations by Rao and Subramaniam (1935) have shown that the two
forms of C. willdenowii [= C. dentata] growing in southern
peninsular India (Madras State) differ strikingly in the composition of
the volatile oil in the leaves. Oil from the leaves of one
form was shown to consist of alpha-, beta-, and di-alpha-clausenan belonging to the furfural group, of which the major constituent was alpha-clausenan. Oil from leaves from a different locality was found to contain not alpha-clausenan but gamma-clausenan, an isomeric substance.
Abundant good herbarium specimens from Madras State, lent to Swingle with other material of Clausena by
the Director of the Royal Botanic Gardens at Kew, show a decided
variation in the shape of the ovary and in the relative length of the
style. A specimen collected by J. S. Gamble (No. 16420,
July, 1885, the Chingleput district of Madras State) shows abundant
flowers with a slender, often conical ovary, 1 to 1.2 mm long and 0.6 to
0.7 mm wide, merging into a cylindrical style distinctly longer, 1.2 to
1.8 mm (all measured dry). Another specimen collected by
Gamble (No. 16190, Barliyár, Nilgiris, at alt. 3,000 ft. [915 m], May,
1885) shows equally abundant flowers with a more or less cubical,
4-angled ovary about 1 by 1 by 1 mm with a prominent oil gland at the
tip of each of the four locules. The cylindrical style does
not merge into the tip of the ovary but is inserted between the four
prominent oil glands; it is only slightly longer than the ovary, 1.1 to
1.2 mm when dry. Another specimen, Wight's No. 354
(collected at Courtallem [Kattalan], July, 1835), has more or less
cubical, 4-angled ovaries with the style distinctly longer, about 1.5 mm
when dry.
Evidently careful research is needed to
distinguish the forms of this and possibly other varieties from the
species. As var. dulcis is of economic importance, it is to be hoped that its taxonomic status can be settled soon.
Other observers agree with Beddome
concerning the delicious character of the fruit of this variety growing
in the western part of Madras State. Thomas A. Bourdillon
(1908, pp. 67, 68), for more than thirty years Conservator of Forests in
the former native state of Travancore, stated: "I agree with Beddome
that the fruit, which very much resembles a grape, is very delicious,
and is well worthy of attention." He found it "common in the
evergreen forests of Travancore at an altitude of 1,000-4,000 ft.
[305-1,220 m] where the rainfall is light. It is a small
tree, 30 ft. [9.14 m] high and 9 in. [23 cm] in diameter, that is
leafless in March, flowers in April and fruits in May and June."
J. S. Gamble, in his Flora of the Presidency of Madras (1915, p. 155), referring to C. willdenowi [= C. dentata], probably in large part this var. dulcis,
stated: "A small tree with glabrous or pubescent leaves, black bark and
white, close-grained wood. The fruit is good and worth
cultivation!"
6d. Clausena dentata var. dunniana (Lév.) Swing. Jour. Wash. Acad. Sci. 30:82 1940. Clausena dunniana Lév. in Fedde, Repert Sp. Nov. 11:67. 1911.
Type.—China, Kweichow Province, Pin-fa (Cavalerie, No. 1072). Herb. Univ. Edinburgh.
Distribution.—China: Kweichow Province.
Leaves 5-11-foliolate; leaflets
elliptical, bluntly pointed at apex, 5-10 X 2.5-3.5 cm, very blunt
(almost truncate) at base, more or less unequal-sided, inconspicuously
crenulate; petiolules unusually long (3-7 mm); inflorescences axillary,
slender; flower buds globose, small, 2 mm diam.; petals glabrous; pistil
2.5 mm long, glabrous; gynophore 0.8 mm long, 0.6 mm wide; ovary
tuberculate, 1 X 1 cm, with 1 or 2 small or medium-sized oil glands in a
tubercule that tips each locule; style cylindric, 0.8-0.9 X 0.5 mm,
narrowed at base; fruits subglobose or short-ovoid, 7-8 X 6-7 mm, black.
Little is known about this shrubby
variety that grows at altitudes of from 200 to 1,200 m. It
may prove to be a good species as yet inadequately
described. The oil glands in the apical tubercles of each
locule of the ovary are somewhat like those of C. dentata,
although usually only one medium-sized oil gland is found in the
species. For the present we are considering this Chinese
plant as a variety of C. dentata, which also has axillary inflorescences.
6e. Clausena dentata var. robusta Tan. Jour. Bot. Brit. & For. 68:228. 1930.
Type.—China, Yunnan Province, Szemao; altitude 1,372 m (Henry, No. 13028). Herb. Kew.
Distribution.—China: Yunnan Province.
Tanaka's original description reads, in
translation, as follows: "A vigorous plant, leaflets large, broadly
oval, unequal-sided rather thick. Inflorescences suberect,
robust. Berry globose, pustulate-punctate."
Tanaka cited two numbers as types: Henry, Nos. 11914D and 13032, both in the herbarium at Kew. The senior author could find only No. 11914D,
which consists of the tip of a fruiting branch with a single leaf and 4
axillary inflorescences, 12-18 X 3.5-4.5 cm. The leaflets
are 8.5-9 X 3-3.8 cm and are acuminate; the berries are subglobose, 7-8
mm diam., borne on a twig 5-7 mm diam., with elongate heart-shaped leaf
scars, 6 X 3 mm. Another sheet in the Kew Herbarium is
Henry's No. 13028, also from Szemao, with flowering twigs with 11
foliolate leaves, 32-37 X 12-14 cm; lateral leaflets 5.5-9 X 3.5-4.5 cm,
terminal 10 X 5 cm; inflorescences 12-14 X 2.5-3 cm; flower buds
globose or obovoid, 2.5 mm long, 2.5-3 mm wide; pistil glabrous, 3 mm
long; gynophore 0.7-0.8 X 0.5 mm; ovary tuberculate, 0.7-0.8 mm wide;
style cylindric, 1.5 X 0.6 mm, stigma depressed, slightly wider than the
style. The leaflets are widely spaced on the rachis (2-4
cm) like those of C. dentata var. dunniana, from which var. robusta is not adequately separated by the brief original description.
6f. Clausena dentata var. henryi Swing. Jour. Wash. Acad. Sci. 30:81. 1940.
Type.—China, Hupeh Province, Ichang (Henry, No. 4122). Cotype: Ichang (Henry, No. 3127). Both in Herb. Kew.
Distribution.—China: known only from western Hupeh and Yunnan (?) provinces.
Differs from C. dentata var. robusta
Tan., from Yunnan, in having hirsute petals, ovate black fruits, and
more densely hirsute young leaves. A small tree, 2-6 m high;
leaves persistent, 25-35 cm long, 13-17-foliolate; leaflets lanceolate,
acuminate at tip, blunt at base, which is often strong (and always
somewhat) unequal-sided, 5-12 X 2-4.5 cm; largest leaflets often
laterals, attached near upper third of rachis; rachis, midribs, veins,
and whole surface of young leaflets pubescent, but leaflets glabrescent
above; inflorescences axillary, sometimes short, 8-10 cm, often longer,
20-25 X 4-6 cm, pubescent when young but soon glabrescent; fruits black
when ripe, ovoid, 9-12 X 6-8 mm.
The fruits of var. henryi are
considered edible in central China, according to Rehder and Wilson
(1914, p. 140). It has been thought by some botanists that
this plant is sometimes cultivated in Hupeh Province. It
should be introduced into culture in other regions and hybridized with
species that produce edible fruits.
7. Clausena harmandiana (Pierre) Guill. in Lecomte, Not. Syst. 1:219. 1910. Glycosmis harmandiana Pierre, Flore Forest. Cochinch. 4(18):text to pl. 285. 1893. Illus. Guillaumin, in Lecomte, Fl. Gén. Indo-Chine 1:664, fig. 70(4-5). 1911.
Type.—French Indo-China, Cambodia (Harmand, No. 3875). Herb. Mus. Hist. Nat., Paris.
Distribution.—Cambodia and Laos. According to Tanaka (1937), it was collected once at Margui, Burma.
The original description by Pierre reads,
translated, as follows: "Branches rounded, pubescent.
Leaves imparipinnate, with 6-9 opposite or alternate leaflets, which are
subdeltoid, ovate-acuminate, obtuse at both ends, 5-14 cm long, 5-8 cm
wide, submembranous, coriaceous, with 7-8 pairs of small lateral
veins. Inflorescences terminal, pubescent, 10-20 cm long,
much branched with rather large (5-6 mm diam.), sessile
flowers. Sepals 1 mm long, very coriaceous, pubescent on the
outside and ciliate. Petals 3.5-4 mm long, very concave,
obovate, veinless, red spotted. Stamens 7-10, 2.5 mm long,
with the filaments flattened below and subulate above, longer than the
anther, which is oval and without an apical gland. Disk
cupuliform. Ovary 2.5 mm long, with 5 locules, each carrying
on the outside 2 large glands. Ovules 2 in each locule."
The description of the disk by Pierre as
cupulate is difficult to credit. A photograph of the
flowering type specimen (Harman, No. 3875) in the Paris herbarium,
placed at Swingle's disposal by Tanaka, led him to think that Pierre
mistook a ring of small bracts at the base of the very short pedicel
(only about 1 mm long) for the calyx and the calyx itself for the
disk! The length of the flower from the base of the calyx to
the stigma measures about 3 mm, the calyx flattened-rotate, about 2 to
2.5 mm wide, tapering rapidly into a very short pedicel about 1 mm long
(including the bluntly conical base of the calyx); at the base of the
pedicel are several small bracts and sometimes one or two small flower
buds which may develop later, or more often abort and fall
off. These bracts and buds are borne on a slender terminal
branchlet of the inflorescence 3.5 to 8 mm long. The ovary
is subglobose or broadly oval, about 1.2 to 1.5 mm long and 1 mm wide;
the style is cylindrical, 0.4 to 0.5 mm long and 0.2 to 0.3 mm wide, not
contracted at the base where it joins the ovary tip. The
gynophore is shorter than in most species of Clausena, but seems to be otherwise normal.
7a. Clausena harmandiana var. contracta Tan. Med. Rijks Herb. Leiden 69:7. 1931.
Type.—Java (Horsfield). Herb. Kew.
Distribution.—Known only from Java.
The type specimen of this variety has 5-7
leaflets varying in size, the lower ones 3-4 X 2-2.5 cm, the larger
laterals 7-9 X 3-3.5 cm and the terminal one 10 X 4 cm, all nearly
equal-sided, broad-elliptical, blunt at both ends, all parts pubescent,
even the upper surface of the leaflets slightly so; inflorescences
terminal, very short, 8 X 3 cm; flower buds globose, 2 mm diam.,
yellowish to reddish-brown when dry; petals without large oil glands at
tips; gynophore 1 mm long; ovary 1 mm long, 1.5 mm wide, jet black,
glabrous; style 0.5 mm long, glabrous, black.
Another specimen in the herbarium at Kew,
identified by Tanaka as this variety (coll. by Zollinger, second Java
voyage, No. 2878), has more glabrous leaves; ovary jet black, very
prominently tuberculate; gynophore subcylindric, abruptly expanding into
the ovary base; style 0.6 mm long, 0.5 mm wide, stigma
depressed-capitate, 0.7 mm wide.
This variety is apparently known only
from these two specimens and is not well understood. Tanaka
(1931b) stated that it resembles somewhat C. dentata var. robusta of China, but differs in having terminal, not axillary, short inflorescences and in having a shorter style and a thicker ovary.
8. Clausena macrophylla Hook. f., Fl. Brit. Ind. 1:504. 1875. Clausena heptaphylla var. (?) pubescens Oliv. Jour. Linn. Soc. Bot. 5(2):30. 1861; C. hirta Ridl., pro parte (?) 1920. Illus. fig. 3-4,G.
Type.—Burma, Trogla, banks of Saluen River (Wallich, No. 6367). Herb. Kew.
Distribution.—Burma; Thailand: Phuket, Tasan; Malay Peninsula.
Hooker (1875, vol. 1, p. 504) described
this species, with some transpositions as follows: "Branchlets as thick
as a goose quill and, as well as the petiole and panicle, clothed with a
soft, spreading, close-set velvety tomentum. Leaves
5-foliolate, 1 ft. [30 cm] long, leaflets 5-7 in. [12.5-17.5 cm] long,
equal or suboblique with very short petiolules, acuminate, obscurely
toothed, small, rather distant teeth, pale on both surfaces, tomentose
beneath, nerves strongly arched, midrib stout, common petiole stout,
terete. Panicle stout, erect, with the peduncle 1 ft. [30
cm] long; branches strict, erecto-patent, secondary branches
short. Flowers glabrous, crowded, 1/10 in. [2.5 mm] diam.,
shortly pediceled, buds globose. Calyx lobes 4, minute,
rounded-acute. Petals broadly oblong, concave, membranous,
covered with large glands. Stamens equal; filaments much
dilated below, very short; anthers large, oblong. Ovary
stipitate, glabrous, 4-lobed, tuberculed with very large glands; ovules
2, collateral in each cell; style as long as the ovary and as broad as
the stigma. Fruit immature, oblong, tip obscurely 4-angled
and truncate."
Ridley mentioned in his description of C. hirta that
the leaflets are "thickly covered with translucent glands and dotted
over with larger, sparser dark brown ones." This description
recalls the dimorphic oil glands of C. guillauminii and makes it very desirable to reexamine all material of C. hirta to see if any confusion has arisen with C. guillauminii, a species which also occurs in Thailand.
9. Clausena anisum-olens (Bl.) Merr. Phil. Gov. Lab. Bur. Bul. 17:21. 1904. Cookia anisum-olens Blanco, Fl. Filip. 359. 1837; Clausena warburgii Perk. Frag. Fl. Phil. 162. 1905; C. loheri Merr. Phil. Jour. Sci. 27:27. 1925.
Type.—Lacking. Substitute type: Rizal Province, Luzon, P.I. (Merrill, Species Blancoanae, No. 1012). Herb. Bur. Sci., Manila.
Distribution.—Philippine Islands: Luzon, Masbate, Basilan, Mindanao islands.
Perkins (l.c.) has drawn up the only full
description of this species yet published. It reads,
translated, as follows: "Shrub or tree, with glabrous…twigs 5 mm thick;
leaves 15-30 cm long, 2-paired…very sparsely gray-pilose; leaflets
ovate, or obovate-oblong or ovate-lanceolate, 6.5-10 cm long, 2.5-3 cm
wide, apex long, narrowly acuminate, the apex itself obtuse or often
subincised, base oblique, papyraceous, glabrous, veins and veinlets
sparsely pilose…lateral veins 8-12 [pairs], veins and veinlets
indistinct above, prominent below. Inflorescences terminal,
paniculate, 18-22 cm long, branchlets numerous, sparsely pilose,
spreading, bractlets ovate, sparsely pilose; flowers 8 mm diam., with
pedicels 5-8 mm long; calyx 5-merous with short lobes…ovate-acuminate,
very sparsely pilose without; 1 mm long; petals with lobes…5 mm long, 2
mm wide, ovate, membranaceous, glabrous on both sides; stamens 9, as
long as the petals, filaments jointed (geniculate) near the middle, the
joint pubescent; disk small, smooth, ovary stipitate, glabrous,
5-locular, 1 mm diam.; style as long as the ovary, stigma sessile,
5-lobed."
Serial microtome sections of the pistil
of a specimen in the Bureau of Science Herbarium at Manila (coll. by E.
D. Merrill, No. 2509, Bur. of Agric., at Lamao River) show the following
characters: Pistils 5-locular, each locule ending in a short process,
bearing at the end a rather large oil gland; ovary broad-oval, about 1.5
mm long, 1-1.2 mm wide; style strongly contracted at base, which is
inserted into a cavity at the tip of the ovary, the rest of the style
unusually broad, nearly 0.8-1 mm wide; the gynophore is long and not
abruptly narrowed, about 1-1.2 mm long, 0.7-0.8 mm wide at the narrowest
place, and about 1 mm at the base and the top.
This species is confined to the main
islands of the Philippines. It has geniculate staminal
filaments, bent at an angle near the middle, slender above the bend and
broader below, resembling somewhat the filaments of C. excavata, but it is much less bent and much less swollen below the bend.
It is related to C. laxiflora of Mindanao Island, Philippines, but shows important differences in the characters of the pistil and the inflorescences.
10. Clausena mollis Merr. Phil. Jour. Sci. Bot. 5:181. 1910.
Type.—Philippines, Luzon Island,
near Bontoc, at 915-1,220 m attitude (Curran, For. Bur., No.
16530). Herb. Bur. Sci., Manila.
Distribution.—Philippines: known only from Luzon Island.
Merrill's original short diagnosis,
translated and supplemented with data from the longer description (in
brackets), reads as follows: "A shrub about 5 m high, all parts densely
and softly pubescent; leaves 20-30 cm long; leaflets alternate or
subalternate, 5-8 on each side, margins entire, base strongly
inequilateral, apex shortly acuminate or…blunt, [lateral veins about 8
on each side of the midrib]. Panicles subterminal, narrowly
pyramidal, flowers 5-merous, sessile or subsessile, subglomerate [on the
ultimate branches]…Sepals broadly ovate, 1.2 mm long, free, densely
pubescent outside. Petals elliptic or broadly
elliptic-oblong, concave, about 4 mm long, 2.5 mm wide, acute at both
ends, imbricate, with few, rather large glands, the back in the upper
third slightly pubescent. Stamens 10, the filaments broad,
abruptly narrowed just below the insertion of the anthers, about 1 mm
long, anthers 2 mm long. Ovary ovoid or ellipsoid, about 1.5
mm long, glabrous, prominently 5-sulcate, 5-celled, each cell with two
superimposed ovules; style 1 mm long and anthers 2 mm long.
Ovary ovoid or ellipsoid, about 1.5 mm long, glabrous, prominently
5-sulcate, 5-celled, each cell with two superimposed ovules; style 1 mm
long and thick [5-sulcate]. Fruits globose, white or
greenish-white, 1-seeded. [Seeds about 5 mm diam.,
surrounded by a gelatinous pulp, with a strong odor and taste of pine
pitch.]"
This species is doubtless related to C. anisum-olens
but differs from it, not only in being densely soft-woolly all over
(except the petals and the flower parts they enclose), but also in
having pistils with a rather short gynophore (somewhat like that of C. laxiflora).
The filaments of the stamens are abruptly expanded from the middle
down, and somewhat geniculate where the slender apical portion joins the
expanded base. Each locule of the ovary is capped by a
single large oil gland. The flowering twigs of this species
are often unusually thick; a specimen collected by Ramos and Edaño (Bur.
Sci., No. 7876), at Mount Masapilid, Bontoc Province, Luzon Island, in
March, 1920, now in the herbarium of the Arnold Arboretum, has twigs 5
to 7 mm in diameter, with reddish-brown pith 2.5 to 3 mm in diameter.
11. Clausena laxiflora Quis. & Merr. Phil. Jour. Sci. 37:154. 1928. Illus. fig. 3-4,M.
Type.—Philippines, Mindanao
Island, Davao Province, Mati (Ramos and Edaño, Bur. Sci., No.
48983). Herb. Univ. Calif., Berkeley.
Distribution.—Known only from the type locality.
Merrill's original diagnosis, translated
with additions from his longer English description (enclosed in
brackets), reads as follows: "A shrub 3-4 m high, scarcely aromatic,
glabrous, or nearly glabrous. Leaves [26-] 39 cm long,
Leaflets 7-9, membranaceous, up to 16 cm long and 6.5 cm wide, ovate,
elliptic, strongly inequilateral [at the base], obtusely
[acuminate]. Inflorescences lax, 30-35 cm long, slightly
pubescent. Flowers 5-merous, about 5 mm diam.
[Calyx shallow, 1.5 mm in diameter, 5-lobed, the lobes broadly ovate,
acute, glabrous, margins sparsely and minutely puberulent.
Petals 5, imbricate, oblong, obtuse, 3.75 to 4 mm long, 2 to 2.5 mm
wide, glandular, glabrous. Stamens 10, about 3 mm long;
anthers oblong, apiculate, about 1.5 mm long; filaments somewhat
enlarged below. Ovary globose, glabrous.]"
This species, so far found only on Mindanao Island, P.I., is obviously related to C. anisum-olens, a species distributed in the Philippines from Luzon Island to Mindanao Island. However, C. laxiflora, besides having larger flower clusters, with longer, more slender branches and much larger leaflets than C. anisum-olens,
shows important differences from the species in the structure of the
pistil, as follows: (1) in having the processes at the tips of the five
ovary locules without large oil glands; (2) in having a much
shorter gynophore, which shows a very short basal annular portion only
about 0.2 mm high and 1 to 1.1 mm wide just below the constriction; (3)
in having locular cavities which descend deeply into the gynophore,
reducing its length to 0.6 to 0.8 mm (instead of 1 to 1.2 mm, as in C. anisum-olens);
and (4) in having a large subglobose ovary, nearly filling the flower
bud, which at this stage has almost no distinct gynophore.
Tanaka (1932e, p. 422) reduced this species to a synonym of C. anisum-olens, but, in view of the striking differences in the ovary and gynophore characters noted above, it is evident that C. laxiflora should be retained as a good species.
12. Clausena todayensis Elmer, Leafl. Phil. Bot. 8:2805. 1915.
Type.—Philippines, Mindanao Island, Davao, Todaya (Mt. Apo) (Elmer, No. 10530). Herb. Bur. Sci., Manila.
Distribution.—Known only from the type, collected on a densely wooded ridge south of the Sibulan River at 1,500 ft. [457 m] altitude.
Elmer's original description reads, in
part, as follows: "Tree, with a 10 m high and 3 dm thick stem…twigs
roughened with lenticels, puberulent when young. Leaves
imparipinnate, thinly coriaceous, paler green beneath, dark green on the
upper conduplicate surface, the acute to acuminate tips strongly
recurved…5 to 7-foliolate…leaflets punctate beneath, slightly
unsymmetric, oblongish…obscurely crenate or undulate, the base obtusely
rounded, the terminal leaflet the larger, the basal pair subopposite and
much reduced, the larger ones 7.5 cm long by 3 cm wide at the middle,
sparsely pulverulent or puberulent on both sides; lateral pairs of veins
5 to 9, divaricat…petiolules only a few mm long, the terminal leaflet
upon a 1 to 1.5 cm long rachis extension. Inflorescence
ascending, terminal, paniculate, 10 to 20 cm long; all the stalks
terete, green, brown puberulent…the ultimate branchlets subtended by
minute bracts; flowers solitary or usually in small terminal clusters,
subtended by a bract…finely ciliate along the margins; pedicel 1 mm
long, relatively thick; sepals 4, cremeus, caducous, elliptically
oblong, 3.5 mm long by one-half as wide across the
middle…glabrous…stamens 8, erect; filaments 2 mm long, fleshy,
compressed, purplish-brown sprinkled, pointed at the apex only…anther
1.5 mm long…emarginate at the apex…ovary more or less rugose, 2 mm long,
short stipitate, obscurely 4-angled and with some large glands,
terminated by a circular stigma."
Tanaka (1932e, p. 423) did not follow Merrill (1923, p. 337) in reducing this to a synonym of C. anisum-olens because, as he stated, C. todayensis has a 4-merous "small ovary, with only 8 large oil-glands somewhat like that of C. harmandiana. The plant is, however, very gracile and not like the above [C. harmandiana]." Pending further study, the species is here retained.
13. Clausena cambodiana (Pierre) Guill. in Lecomte, Not. Syst. 1:219. 1910. Glycosmis cambodiana Pierre, Flore Forest. Cochinch. 4(18):text to pl. 285. 1893.
Type.—French Indo-China, Cambodia,
Knang-Krêpeuh Mountains at 1,500 m altitude (Pierre, No.
832). Herb. Mus. Hist. Nat., Paris.
Distribution.—Known only from the type locality.
The description given by Guillaumin
(1911, p. 665) reads, translated, as-follows: "A small tree 5-8 m
tall. Branches glabrescent. Leaves 15-20 cm
long, with 5-11 alternate, glabrous, membranaceous leaflets, equilateral
at the base, oval or oblong-lanceolate, 9-15 X 3-5 cm, cuneiform at the
base, cuspidate at the apex, with 6-9 pairs of lateral veins, which
like the veinlets are visible above and are raised below; petioles
cylindrical, pubescent; petiolules cylindrical, about 5 mm
long. Fruiting inflorescence a terminal panicle, as long as
the leaves, pyramidal, pubescent. Fruit spherical,
red-violet, about 8 mm diam., punctate because of the oil glands, very
fragrant."
In the original description Pierre
mentioned that the lower leaflets are smaller and that the fruiting
inflorescences are 20 cm long.
A photograph of the type specimen
(Pierre, No. 832) preserved in the Paris herbarium, made by Tanaka,
shows the leaves taper to a very sharp tip 0.9 to 2 mm wide, and are
very flat and entire-margined. The fruits are borne on
slender pedicels about 4 to 6 mm long, arising from nearly straight,
rather stiff lateral branches of the inflorescence, 7 to 8 cm long below
but much shorter above. Most of the other species of Clausena having caudate leaflets have the margins of the leaflets minutely dentate or crenulate (as in C. dentata) or else have curved tips and very unequal-sided bases (as in C. wallichii).
14. Clausena brevistyla Oliv. Jour. Linn. Soc. Bot. 5(2):31. 1861.
Type.—Australia, Queensland, Hope Islets (MacGillivray, July 18, 1848). Herb. Kew.
Distribution.—Australia: Queensland.
Oliver's original description reads:
"Leaves 10-15-foliolate, leaflets very oblique; ovary more or less
obovate, narrowed at the base, 4-lobed above, glabrous or almost
glabrous; style distinct from the ovary, very short, half shorter than
the ovary, equal to the stigma [in diam.] Shrub (?). Leaves
5-8 in. [12.5-20 cm] long. Petiolules about 2 lin. [4 mm]
long. Leaflets oblique or rhomboid-oval or ovate, apex
scarcely acuminate, margins undulate-crenate or dentate, glabrous or in
young leaves pubescent near the midrib, 1-4 1/2 in. [2.5-11.5 cm] long,
10 lin. to 1 1/2 in. [20-38 mm] wide. Calyx 4-5 parted,
lobes widely ovate. Petals 4-5, thin, broadly elliptical or
rounded. Stamens often 10, filaments thicker below and
dilated, somewhat arched. Ovary glabrous, or with few hairs,
4-5-locular. Ovules 2 (superimposed?). Stigma
equal to the style [in diam.]. Fruit not seen.
Resembles C. heptaphylla very closely, differing in the
conspicuous obliquity of the leaflets and the very short style, inserted
in both species in the central apical depression of the
ovary. The flowers are often pentamerous."
This species is the only one native to
Australia and thus occupies the extreme southeastern portion of the
range of the genus Clausena.
14a. Clausena brevistyla var. halmaheirae (Miq.) Swing. Jour. Wash. Acad. Sci. 30:82. 1940. Clausena halmaheirae Miq. Ann. Mus. Bot. Lugd.-Bat. 1:211. 1863.
Type.—East Indian Archipelago; Moluccas, Halmahera Island (Teijsmann and De Vriese), Rijks Herb., Leiden.
Distribution.—Known only from the original collection.
The original description by Miquel reads,
translated, as follows: "Branches, petioles, and midribs (on lower
side), along with the inflorescences, covered sparingly with a thin
adpressed pubescence; leaves long, with rather widely separated
leaflets; leaflets (on the stronger leaves up to 11, or fewer) with
short petiolules, lower ones nearly opposite, broadly obovate and
shortened, the others not opposite, narrowly sublanceolate-oblong,
acutely pointed toward the base, one side cut off, the other obtusely
unequal-sided, chartaceous with even or slightly repand margins;
sometimes very minutely subserrate, pale, black glandular-punctate
below, with 10-15 spreading veins; fruiting inflorescences axillary, 1/2
longer than the leaves, with lax few-flowered branchlets; calyx
4-lobed; immature berries, 1-seeded. Near to the species
which I listed in Fl. Ind. bat., Suppl. I, p. 501, doubtfully under the
name C. excavata. Sufficiently distinct from all
described species, but recalling several of them. Leaves
1-1.5 ft. [30-45 cm] long. Lower leaflets 3 in. [7.5 cm]
long, upper ones 6-6.5 in. [15-17 cm] long."
Tanaka (1931b, p. 6) who examined
the type specimen at Leiden and other type material at Utrecht and Kew,
concluded that this plant "is closely related to C. harmandiana,
but is different in having narrower leaflets with distinct black dotting
and a long branched panicle bearing [a] decidedly smaller
berry." With respect to the last-named character, Miquel
noted that the type material (all that is known as yet) has immature
fruits.
This variety is characterized by having
large fruiting inflorescences with widely spreading primary branches and
sturdy terminal pedicels 2 to 4 mm long. It has very small
pistils, only 1.4 to 1.5 mm long (in dry state), with a very slender
gynophore, only 0.2 to 0.3 mm in diameter, and an ovary only 0.8 mm long
and 0.6 mm wide, rough with oil glands, and a cylindrical style,
shorter than the ovary. The leaflets are only slightly
unequal-sided. This variety is very distinct from C. harmandiana.
15. Clausena anisata (Willd.) Hook. f. Niger Fl. 1:256. 1849. Amyris anisata Willd. Sp. Pl. 2:337. 1800. Illus. De Wildeman, Ann. Mus. Congo, Bot 5 sér. 2: pls. 52, 53. 1907.
Type.—Western Africa, "Guinea" (coll. ?). Herb. Bot. Mus., Berlin-Dahlem.
Distribution.—Western Africa:
Sierra Leone to Angola; central Africa: Bahr-el-Ghazal and Pemba through
Usambara to northern Malawi and Tanzania on Masai plateau, reaching
3,000 m altitude.
This Species was described by Oliver
(1861, p. 34) from Nigerian material as follows: "Leaflets 10-20,
panicles lax, elongate, shorter than the leaves or longer, lateral
branches divaricate in a cymose manner, slender, pubescent; ovary
4-furrowed, 4-loculed; ovules paired [in each locule], obliquely
superimposed or almost collateral.…Small shrub 3 ft. [92 cm] high with
white flowers. Leaves 6-12 in. [15-30 cm] long; leaflets
unequal-sided, obliquely ovate or ovate-oblong, obscurely crenulate,
sometimes slightly acuminate or emarginate, pubescent.
Inflorescences paniculate, 6-9 in. [15-23 cm] long, borne in the axils
of the upper leaves. Pedicels 2/3-1 lin. [1.2-2 mm]
long. Bractioles minute, ovate or lanceolate.
Calyx 4-merous, lobes ovate. Stamens with filaments abruptly
dilated in the middle, subulate above. Ovary
short-stipitate, glabrous. Style rather long, rather thick,
4-furrowed, separating at the base."
This species is the only one found in
western Africa, but in eastern Africa it shares the central part of the
range of the East African C. abyssinica. All three African species vary greatly and have ill-defined varieties.
Engler (1931, p. 322) reported that in western Africa C. anisata
is found in the scattered bush forests of the hinterland of Cameroons
(now Cameroon), where it is a tree 15 to 20 m high at an altitude of
2,100 m. Engler found that in eastern Africa it reaches the
very considerable altitude of 3,000 m (9,840 feet), where it grows in
the mountain meadows as a beautiful tree of medium height with a broad
crown. This is by far the highest altitude yet reported for
any member of the orange subfamily, but since Mount Kilimanjaro is
situated only 30° 37' south of the equator, even at high altitudes no
severe cold in winter is experienced there.
Clausena anisata and C. inaequalis were separated by Engler (1931, p. 322) by the length of the inflorescences in relation to the length of the leaves: in C. anisata the flower clusters are much longer than half the length of the leaves; in C. inaequalis they are never more than half the length of the leaves. De Wildeman and Durand (1901, p. 743) found the leaves of C. anisata to be 15 to 40 cm long, those of C. inaequalis to be 7.5 to 25 cm long; and the flowers of C. anisata to occur in many-flowered paniculate cymes, but those of C. inaequalis in
three-flowered clusters or singly along the racemes. These
two species have similar, more or less obovate or pyriform ovaries, with
a large gland at the tip of each locule.
15a. Clausena anisata var. multijuga Welw. ex Hiern. Cat. Welw. Afr. Pl. 1:116. 1896.
Type.—Africa, Angola, Golungo Alto (Welwitsch, No. 1320, in part; coll., Nov. 1855). Herb. Brit. Mus., London.
Distribution.—Angola: reported only from Golungo Alta and Pungo Andongo, in elevated stations up to 2,200 ft. [670 m].
Differs from the species chiefly in
having leaves with more numerous leaflets (17-32). A shrub
or "small tree 7-12 ft. [2-3.6 m] high, with slender, far-reaching,
almost sarmentose branches, with a very short, closely-set
pubescence." Leaves 3-10 in. [7.5-25 cm] long; leaflets
1/2-2 X 1/6-5/8 in. [1.2-5 X 0.4-1.5 cm]; inflorescences 4-9 in.
[10-22.5 cm] long.
It is doubtful whether this small-leaved
multifoliolate form deserves taxonomic recognition. No
mention is made of tubercules on the ovary such as are found in a form
growing a few hundred kilometers to the north in the Congo Valley;
presumably the ovary in var. multijuga is smooth.
This Angola form is said to make a small,
elegant tree. It should have value as an ornamental tree
for cool subtropical regions. The leaves are "fragrant when
rubbed, emitting a very agreeable aroma like that of oranges and
lemons." The flowers are white but small.
15b. Clausena anisata var. mollis Engl. Die Pflanzenwelt Ost-Afrikas C:228. 1895; also in Die. Nat. Pflanzenfam. ed. 2. 19a:322. 1931.
Type.—Africa (locality doubtful). Herb. Bot. Mus., Berlin-Dahlem.
Distribution.—Africa: forest and
bush steppes of Cameroon hinterland; the Lake Region; Tanzania, Mount
Kilimanjaro, western Usambara, coastal region; northern Malawi.
Leaves soft-pubescent and with blunter leaflets than the species.
An inadequately known plant that needs study.
16. Clausena inaequalis (DC.) Benth. in Hook., Niger Fl. 1:257. 1849. Elaphrium inaequalis DC. Prodr. 1:724. 1824; Amyrisinaequalis Spreng. 1825; Fagarastrum inaequalis Don. 1832; Myaris inaequalis Presl. 1840. Illus. Wood & Evans, Natal Pl. 1(2):54, pl. 66. 1899; Sim, For. Fl. Cape Col. pl. 26. 1907.
Type.—South Africa (coll. ?). Herb. De Candolle, Geneva.
Distribution.—Southeastern Africa: Cape Colony, Pondoland, Natal, with transition forms to C. abyssinica (fide Engler, 1931, p. 322).
This species was described by Wood and
Evans (1899, p. 54) as follows: "A shrub or small tree with dark
coloured bark, which is usually thickly studded with
lenticels. Leaves unequally pinnate, 6-8 in. [15-20 cm]
long; leaflets alternate or subopposite, in 4-6 pairs, petiolulate,
glabrous, lateral ones very unequal-sided, the lower portion of the
lamina being much smaller than the upper portion, terminal one subequal,
broadly lanceolate, margin unequally crenate, attenuate to an obtuse or
subacute apex; 1 1/2-2 in. [3.8-5 cm] long; 1/2-3/4 in. [13-18 mm]
broad, petiolules 2-3 lin. [4-6 mm] long, pubescent, terminal one 6-9
lin. [12-18 mm] long, swollen and bent below the lamina.
Flowers paniculate, white. Calyx small, 4-parted, sepals
lanceolate, pubescent. Petals 4, concave, free, spreading,
imbricate in bud, deciduous. Stamens 8, hypogynous,
filaments free, subulate, flattened. Anthers
sagittate. Ovary on a short cylindrical fleshy torus,
obtusely 3-lobed, 3-celled, ovules 2 in each cell,
collateral. Style short, thick, deciduous.
Stigma 3-lobed. Berry fleshy, dark purple, the epicarp
thickly studded with minute glands; 1-2 seeded by abortion."
Clausena inaequalis varies greatly, as do the other African species, C. anisata and C. abyssinica.
The first two differ in the length of the leaves, the obliquity of the
leaflets, the length of the inflorescence compared to the length of the
leaves, and the number of flowers arising in the ultimate division of
the inflorescence; C. abyssinica is discussed below.
17. Clausena abyssinica Engl. Die Pflanzenwelt Afrikas 3:757. 1915. Clausena inaequalis var. abyssinica Engl. Die Pflanzenwelt Ost-Afrikas C:229. 1895. Illus. fig. 3-4,H.
Type.—Abyssinia, plateau up to 2,300 m altitude (coll. ?). Herb. Bot. Mus., Berlin-Dahlem.
Distribution.—Eastern Africa: Ethiopia; Tanzania, Mount Kilimanjaro (up to 2,800 m alt.); southern Malawi; Zambia.
The brief original description of the
variety reads, translated, as follows: "leaflets less unequal-sided,
more acuminate [than in the species C. inaequalis].—3 [Abyssinian
plateau] (2,300 m).—15 [Mount Kilimanjaro, Tanzania] (2,700 m).—A tree
up to 10 m high in mountain forests." The laconic
description of the species in Engler's account of Clausena (1931, p. 322) characterizes C. inaequalis as having "very unequal-sided, rhombic-ovate, mostly blunt pointed" leaflets, and C. abyssinica as having "usually oblique-lanceolate leaflets and larger flowers."
Clausena abyssinica was reported
by Engler (1931, p. 322) as growing up to 2,300 m in the Abyssinian
plateau and up to 2,800 m in the upper girdle-forests of Mount
Kilimanjaro in Tanganyika (now Tanzania). This altitude is
exceeded only by C. anisata, which on Mount Kilimanjaro attains
3,000 m. These two species hold the altitude record for the
orange subfamily, and they must be able to grow at lower mean and
maximum temperatures than any other Citrus relatives.
A critical comparative study of C. inaequalis and C. abyssinica is urgently needed. The original description of C. abyssinica as a species contradicts the original description of it as a variety in stating that the leaflets are more oblique than those of C. inaequalis instead of less oblique! As a matter of fact, all three African species of Clausena (nos. 15 to 17 above) and their varieties are exceedingly variable and as yet inadequately described.
Engler (1915, p. 757) noted the difficulty of separating the African species and varieties of Clausena in
an eloquent sentence to the effect that it is as hard to separate the
species as it is easy to recognize the genus, which is spread over
Africa from Ethiopia to Cape Province and from upper Guinea to Angola.
18. Clausena papuana Lauterb. Bot. Jahrb. 55:259. 1918.
Type.—Northeastern New Guinea, at
the foot of the Bismarck Mountains (Schlechter, No. 18476).
Herb. Bot. Mus., Berlin-Dahlem; fragments in the Lanterbach Herbarium in
the Herb. Bot. Inst., Univ. Breslau.
Distribution.—Known only from the original collections made by Schlechter.
Lauterbach's original description of this
species reads, translated, as follows: "Small tree with rounded twigs,
the young shoots tomentose. Leaves alternate, imparipinnate,
rachis tomentose. Leaflets alternate…petiolulate,
oblique-ovate, obtusely subacuminate, the upper half rounded at the
base, the lower half acute at the base, membranaceous, punctate, showing
veins on both sides in the dried material, margins inconspicuously
crenulate, lateral veins (8 pairs) oblique, curving and fusing together
near the margins; midrib slightly elevated below. Panicles
axillary, subterminal, as long as the leaves, main stems tomentose,
branches more or less separated, ending in aggregated apical branchlets,
flowers short-pedicellate, in heads (‘capitulate’). Sepals
4, connate at the base, acutely triangular, tomentose without; petals 4,
elliptic-acute, glandulose, glabrous, reflexed in anthesis; stamens 8,
nearly equal in length, filaments thickened at the base, anthers
elliptical, emarginate; gynophore glandulose; ovary glabrous, cylindric,
somewhat quadrangular, locules 4, each with 2 ovules; style short,
stigma dilated. A small tree with twigs 4 mm diam., having
gray-brown bark. Leaves 30 cm long; rachis 3 mm diam. at
lower end; petiolules 4-5 mm long. Leaflets 5-11 cm long,
3-5 cm broad, smallest at the base of the leaf.
Inflorescence 30 cm long, stem 7 cm, branches 2-3 cm, and flower stalks
1-2 mm. Flower buds 2.5 mm diam.; calyx lobes 0.5 mm long,
petals 4 X 2 mm. The tip of each petal bears a large oil
gland which, in the bud seen from above, forms a cross with those of the
other petals. Stamens 4 mm long, of which the anther
measures 1.5 mm. Gynophore 0.5 mm high, ovary 1 mm high, the
style with the stigma 1 mm long."
Lauterbach noted at the end of the original description that "this species approaches [C.] brevistyla
Oliv. from Queensland. It differs from it in its hairiness,
larger leaves with broader, blunter leaflets and much larger flower
clusters arising in the axils of the uppermost leaves."
Tanaka (1928c, p. 141) reduced this species to a variety of C. harmandiana
(see p. 177), but, as he pointed out, this latter species has fewer
leaflets (5 to 7 instead of 10 to 11, or more) and a less hairy
rachis. Swingle found the leaflets of C. harmandiana much less unequal-sided at the base than those of C. papuana. The flowers of C. harmandiana have remarkably short pedicels, only about 1 mm long, whereas the pedicels of C. papuana are usually about 2 mm long. Clausena harmandiana
has a very short, inconspicuous gynophore (Pierre apparently did not
see it!), probably only 1/3 to 1/2 mm long, whereas the gynophore of C. papuana
is better developed, about 1/2 to 3/4 mm long, and is easily
seen. Serial microtome sections made from the type material
(Schlechter, No. 18476) preserved in the Lauterbach Herbarium and kindly
lent Swingle by the Botanical Institute of the University of Breslau
show that each locule of the ovary is tipped by a single large oil gland
(not two as in C. harmandiana); each anther, each petal, and each sepal also has a large oil gland at the tip.
19. Clausena guillauminii Tan. Bul. Mus. Hist. Nat. Paris, 2 sér. 2:161. 1930. Illus. fig. 3-4,L.
Type.—Thailand, Udawn, Lôti, Wang Sapung (Kerr, No. 8782). Herb. Kew.
Distribution.—Thailand, Laos.
Tanaka's original description reads, in
translation, as follows: "Shrub; branchlets and leaf veins
pellucid-dotted and puberulous. Leaves 1-5-foliolate, rachis
narrowly winged; leaflets alternate, thick, obovate or oblong, base
acute or rather obtuse, apex cuspidate, obtuse or rather acute, lateral
leaflets smaller, nearly equal-sided, terminal leaflet sometimes much
wider, all sparsely black-dotted, conspicuously reticulate, slightly
crenate-serrate. Inflorescences terminal, paniculate,
lateral peduncles short, about equal in length. Flowers
small, 5-merous, petals and calyx lobes pellucid-spotted at the
tips. Filaments subulate, anthers
glandulose-tipped. Ovary ciliate, with 2 series of
glandulose spots, short-stipitate; style long, stigma subcapitate."
The type and cotype material collected in
Thailand by A. F. G. Kerr (his Nos. 8782 and 8388, listed by Tanaka),
which was lent to Swingle by the Director of the Royal Botanic Gardens
at Kew, shows the following dimensions: Compound leaves (No. 8782),
5-7-foliolate, 17-20 X 9-13 cm, rachis 9.5-11 cm long, 1-1.5 mm diam.,
narrowly margined (0.2-0.5 mm) between the leaflets; terminal leaflets
7.5-9.5 X 4.3-5.7 cm; lateral veins 9-12 pairs, nearly straight; lateral
leaflets 3-8 X 2-4.2 cm. Unifoliolate leaves (No. 8388),
7.5-10.5 cm long, usually long-elliptical, blunt or subacute at both
ends, petioles 1-3.5 cm long, very narrowly margined; inflorescences
3-10 cm long, but only 1-2.5 cm wide. This plant has stems
only 20-30 cm high and 3.5 mm diam., springing from a root 1 cm diam.,
yet they were flowering freely and were bearing a few fruits when
collected February 3, 1924.
Craib (1926, p. 233) stated concerning
this material: "The glands on the leaves are by far the largest of any
Siamese rutaceous plant seen. The sepals and petals all have
one prominent gland much larger than the others and the ovary has five
conspicuous glands at the apex and usually a few longish spreading
hairs."
Serial microtome sections of a specimen
collected by Kerr (No. 8782) at Me Chan, Chien Sen, Thailand, show that
there are smaller irregularly placed oil glands around the side of the
ovary about at the point where the gynophore ends; there are 7, 8, or
more of them, and they, along with the much larger oil glands that are
borne in processes at the tip of each locule, must be what Tanaka had in
mind in describing the ovary as "marked with two series of glands."
This species is said to be a shrub
growing only 20 to 40 cm tall by Thorel, who collected it in
Laos. Possibly it is killed to the ground by annual fires
and springs up each year from the root. The oil glands are
dimorphic, most of them being small, but a few, scattered 3 to 4 mm
apart, being much larger, l/3 to 1/2 mm in diameter, pale on young
leaves but dark brown or nearly black on old leaves. By
transmitted light, such glands are bright, clear red in color, about
Jasper Red of Ridgway (1912, pl. 13). These large oil glands
are often conspicuously convex and stand above the leaf surface; they
are sometimes surrounded by many small veinlets that radiate out from
the oil gland.
This astonishing species merits careful
study as it differs widely from almost all the others of the
genus. Two other species, C. papuana and C. wallichii,
have the same distribution of oil glands on the floral organs, viz., a
single, rather large oil gland on the tip of each calyx lobe, on each
petal apex and another [sic] tip, as well as a short-stalked oil gland at the top of each locule of the ovary. C. papuana has very different leaves with about twice as many leaflets and a wingless rachis, whereas C. wallichii has acuminate, crenulate or denticulate leaflets about twice as large.
20. Clausena wallichii Oliv. Jour. Linn. Soc. Bot. 5(2):35. 1861. Illus. Swing. Jour. Wash. Acad. Sci. 30:81, fig. 2. 1940.
Type.—Burma, Chapedong Hill (Wallich, No. 6370). Herb. Kew.
Distribution.—Burma: eastern Himalayan region, Tenasserim; Thailand.
The original description by Oliver (1861,
p. 35) reads, translated, as follows: "Leaves with the rachis narrowly
winged; leaflets rhomboid-lanceolate, or oblong, acuminate, glabrous,
margins crenulate. Inflorescences paniculate, many-flowered,
branches close together, flowers few. Calyx 5-merous, lobes
ovate. Petals 5, margins slightly imbricate in the bud,
thin. Stamens 10, free, filaments thickened at the middle,
at first slightly arched below. Ovary short and narrowly
stalked, 5- (or 4-) locular, ovules obliquely superimposed.
Style very short, furrowed, equaling the stigma in width."
The brief diagnosis adds the following characters: "Leaves 13-17
foliolate…Style distinct from the ovary, shorter or almost as long…"
Hooker (1875, vol. 1, p. 505) added a few
characters as follows: "Leaves 8-12 in. [20-30 cm] long; leaflets 2-3
in. [5-7.5 cm] long, alternate, oblique, caudate-acuminate, with an
obtuse notched tip, narrowed into a cuneate base. Panicle
3-5 in. [7.5-12.5 cm] long, and broad, much branched…Flowers subsessile,
1/8 in. [3 mm] diam.…ovary glabrous."
An examination of the type specimen and
much other material of this species lent to Swingle from the Kew
Herbarium and from the Calcutta Botanic Garden enabled him to add
several characters, as follows: Leaves 20-30 X 7-12 cm; leaflets 6-10 X
2-4 cm, crenulate or denticulate, very unequilateral, turning brown on
drying, with numerous evenly distributed oil glands varying greatly in
size (about 0.04-0.2 mm diam.); flowers 4.5-5 mm long from base of calyx
to tip of stigma, flower parts all heavily impregnated with tannin
residue, glabrous, except ovary; calyx lobes, petals, anthers, and 5 (or
4) locules of the ovary each tipped with a single large oil gland;
ovary tuberculate, often bearing a few rather long hairs, about 1.8-2 X
0.8-1.2 mm; style 1.8-1.9 X 0.4-0.5 mm; gynophore 0.7-0.8 mm long,
0.5-0.8 mm diam. at narrowest part; pedicel of flower 1-2 mm long with
minute ciliate bracts at base; fruits subglobose or round-ovoid, 5-6 X 5
mm (immature?), borne on pedicels 2-3 mm long and 0.8-1 mm thick.
This species has the rachis very narrowly
winged (wings 0.3 to 1 mm wide), a peculiarity it shares with C. guillauminii, which usually has the rachis merely margined rather than winged, whereas in C. luxurians the
rachis is plainly winged (wings 1 to 2.5 mm wide). The
floral organs, calyx lobes, petals, anthers, and ovule locules, are each
tipped with a single large oil gland, in this character resembling C. guillauminii and C. papuana. The great variation in the size of the oil glands of the leaflets resembles but does not equal that found in C. guillauminii. There can be little doubt that C. wallichii, C. luxurians, and C. guillauminii are rather closely related species, and all of them may be distantly related to C. papuana.
21. Clausena luxurians (Kurz.) Swing. Jour. Wash. Acad. Sci. 30:79. 1940. Clausena wallichii var. luxurians Kurz, Jour. Asiat. Soc. Bengal 44(2):133. 1876. Illus. Swing. loc. cit., 30:80, fig. 1.
Type.—Burma, Pegu, Choungmenah
(Kurtz. No. 1995). Herb. Bot. Gard., Calcutta. A
sheet marked with Swingle and Tillson's serial microtome sections No.
519.
Distribution.—Southern Burma: known only from Pegu and Tenasserim.
A shrub, with large leaves, 30-50 X 20-27
cm, 5-7- (often 6-) foliolate; leaflets small and broad at base of
rachis, 6.5-7.5 X 4-5 cm, larger, lanceolate-acuminate near tip of
rachis, 15-21 X 6.5-8.5 cm, base acuminate and decurrent on petiolules,
entire-margined, only slightly unequal-sided, terminal leaflet
symmetrical at base, largest of all, 15-21 X 6.5-9.5 cm, lateral veins
varying greatly in prominence, heavier ones few (7-9), arising at angles
of about 70°-75° with the midrib, smaller intermediary lateral veins
usually arising at a much greater angle (often 80°-85°) with the midrib,
margins entire or subcrenate, surface covered with numerous oil glands
varying in size from 0.04 to 0.2 mm, rachis narrowly but clearly winged
except the segment below the lowest leaflet, wing broader (1.2-2.5 mm)
at top of each rachis segment where leaflet is attached, smaller (0.8-1
mm) at the base of the rachis segment; inflorescences usually terminal,
short, about 8-12 X 4-6 cm; flowers white, small, about 4-5 mm diam.,
2.5-3.5 mm long from base of ovary to stigma; flower buds subglobose,
all flower parts glabrous, free from tannin, pale amber-colored when
dry; calyx lobes, anthers, and ovary locules each tipped with a single
large oil gland; pistil small, about 2.5-3 mm long; gynophore well
developed, hourglass-shaped, 1 mm long, 0.6-0.8 mm wide at narrowest
point; ovary tubercular at base, 1-1.1 mm long, 1-1.3 mm wide, with one
large oil gland at top of each locule, not blending with the style,
which is narrowest at base, 1.1-1.3 X 0.4-0.6 mm; fruits (immature)
subglobose, 5-6 mm diam.
The abundant material of this plant
collected by S. Kurz at Choungmenah, Pegu (under No. 1995), was labeled
by him C. wallichii var. luxurians. A
collection made by A. Meebold (No. 15090), at Wagôn, Tenasserim (in
Herb. Bot. Gard., Calcutta, and also in Herb. Bot. Gard., Breslau), has
somewhat smaller leaves than the Pegu material and even smaller
inflorescences (6 by 3 cm). The fact that both C. wallichii and C. luxurians
have leaves with a winged rachis, an unusual character in the tribe
Clausenae, has probably operated to cause most taxonomists to class them
as mere forms of one and the same species.
Serial microtome sections of the pistils
show several important differences between these two species in the
absolute and relative size of the flower parts; moreover, C. wallichii has abundant tannin deposits scattered through the tissues, whereas C. luxurians shows none. The leaflets of C. luxurians are decidedly fewer and much larger than those of C. wallichii and differ also in shape and margination. The flowers of C. luxurians, however, are decidedly smaller than those of C. wallichii and the petals are not each clearly tipped by a single large oil gland.
22. Clausena lenis Drake, in Morot, Jour. Bot. 6:276. 1892. Clausena kerrii Craib, Kew Bul. Misc. Inform. 1913:67. 1913. Illus. Guillaumin, in Lecomte, Fl. Gén. Indo-Chine 1:664, fig. 70(6-7). 1911.
Type.—French Indo-China, Tonkin, Tu-phap (Balansa, No. 3667). Herb. Mus. Hist. Nat., Paris.
Distribution.—North Vietnam: Tonkin; Laos; Thailand: Pâyap; China: Yunnan Province.
A rather full description of this species
by Guillaumin (1911, p. 663) reads, in translation, as follows: "A
shrub completely covered by soft pubescence (except the upper surface of
the leaflets). Leaves 35-40 cm long, with 11-17 alternate
leaflets, very unequal-sided at the base (except the terminal one),
membranaceous, oval (2.5-12 X 2.5-6 cm), acute at the base, obtuse at
the tips with the margins indistinctly denticulate, glabrous above
(except the midrib and lateral veins), completely soft-pubescent below,
lateral veins 5-8 pairs, slightly raised on the underside; veinlets not
visible, petiolules about 1 cm long, petiole cylindric, slightly
glandular. Inflorescence a pyramidal, pubescent, terminal
panicle shorter than the leaves, with alternate branches, pedicels
soft-pubescent, as long as the flower, without visible articulations;
flowers 3-4 mm long, flower buds ovoid. Sepals 4, small,
oval-obtuse, slightly pubescent without, ciliate at the
margins. Petals 4, glabrous, oval, glandular.
Stamens 8, equal, almost as long as the petals, anthers lanceolate, with
2 linear locules each ending in a point, staminal filaments flattened
and broadened, very short, glabrous. Ovary glandular, almost
completely glabrous, locules 2, with 2 superposed ovules in each, style
cylindrical, as long as the ovary. Fruit unknown."
In his description of C. kerrii, now considered a synonym of C. lenis,
Craib (l.c.) added a few details to Guillaumin's description, as
follows: "Shrub up to 3 m high, twigs up to 5 mm diam., with soft short
white pubescence…Leaves 50 cm long, petiole up to 6.5 cm long, lower
leaflets 4.6 cm long, 3.2 cm wide, upper leaflets up to 14 cm long and 6
cm wide…Inflorescences…bracts about 1.5 mm long…Petals white (fide
Kerr), oblong-ovate, 5 mm long, 2.7 mm wide. Stamen
filaments 0.75 mm long, anther 3 mm long. Ovary 1.25 mm
high, style 2.5 mm long, provided with a very few hairs, here and
there."
The Chinese form may be described as
follows: Small tree, 2-3 m high; twigs stout, 5-6 mm diam., at first
angled, soon becoming terete, finely puberulent, soon glabrescent;
leaves large, 30-65 cm long, with 11-15 leaflets (usually 13-15), rachis
minutely puberulent; leaflets very unequal-sided at base,
oblong-lanceolate and acuminate or even subcaudate, cuneate at base,
varying greatly in size on the same leaf, lower ones sometimes only
2-2.5 X 1.5-2 cm, those in the middle of the leaf largest, 10-13 X 3.5-5
cm, terminal leaflets 8-10 X 2-3.5 cm, lateral veins 6-8 on apical half
and 5-6 on basal half on the larger leaflets, margins dentate, except
near the base, midrib and lateral veins minutely puberulent, petiolules
2-4 X 1 mm, leaf margins more or less decurrent on sides; inflorescences
terminal, or axillary among reduced leaves at the end of the flowering
branch, 15-28 cm long and 10-15 cm wide when terminal, 5-15 X 2-4 cm
when axillary, ultimate branchlets bearing pedicels 4-8 X 0.5 mm in dry
state, entire inflorescence minutely puberulous; flower buds ovoid,
light coffee brown in dry state; calyx very small, 4-lobed, lobes
semicircular, 0.8-0.9 mm wide, 0.5-0.6 mm long, puberulous; corolla
4-merous, petals thick, coriaceous, entire, incurved at tips, 4-5 X 3-4
mm, glabrous, dotted with small oil glands; pistil 4 mm long in the
flower bud, 5-6 mm long after petals and stamens fall; gynophore 1 mm
high with a short annulus at the base 1.2 mm wide, 0.35-0.5 mm high,
narrow constriction above annulus 0.8-0.9 mm wide, upper part of
gynophore cylindrical, 1.2 mm wide, 0.7-0.8 mm high, merging with the
equally wide base of ovary at top but with a complete ring of 12-15 oil
glands at the base just above the constriction; ovary cylindrical below,
1.2 mm diam., slightly narrowed and rounded at top where a pit, 0.5 mm
wide and 0.2-0.3 mm high, bears the style, slightly narrowed where
attached, surface covered with numerous slightly prominent oil glands
and sparingly hirsute, style cylindrical, 0.5-6 mm diam., and 3.5-3.8 mm
long with no clearly marked stigma, ovules collateral, 2 in each
locule. Staminal filaments very short, anthers very long
(4-5 mm), slender with a single elongated oil gland at back where
filament is attached; fruit (immature) subglobose or slightly ovoid,
strongly dotted with oil glands, 5-8 mm diam.
In Thailand, this species has scattered
hairs toward the base of the style. The ovary is said to be
entirely glabrous, but in Tonkin, North Vietnam, it is apparently
occasionally slightly hairy, to judge from Drake's
description. In Yunnan Province, the ovary usually bears
scattered, rather long hairs which often fall away as the young fruit
develops, but the style is usually completely glabrous. The
type specimen from Tonkin shows rather blunt-pointed leaflets with
undulate margins; the Siamese material (C. kerrii Craib) has
acutely pointed or acuminate leaflets with faintly and distantly
serrulate margins; and the Chinese plant shows acuminate or caudate
leaflets with rather strongly dentate-serrulate margins. The
length of the style varies somewhat also, being shortest in the Tonkin
type and longest in the Chinese material.
This remarkable species is very different from any others of the genus, as noted above;
it has evidently gone some distance on an independent line of evolution
distinct from that followed by any other known member of the tribe
Clauseneae.
23. Clausena suffruticosa (Roxb.) Wt. & Arn. Prodr. 96. 1834. Amyrissuffruticosa Roxb. Fl. Ind. 2:250. 1832.
Type.—None found; type plant sent from Chittagong, northwestern Burma, to Calcutta Bot. Garden.
Distribution.—India: eastern Himalayan region, Khasi Hills; Burma: Chittagong.
An undershrub with simple stems, often
only 1-2 ft. [30-60 cm] tall, with all the younger parts softly
pubescent; leaves 30-40 cm long; leaflets 11-17, densely soft-pubescent
when young, when older glabrescent, lower ones ovate, equal-sided,
subopposite, 2-4 X 1-2 cm, with entire margins, upper ones alternate,
slightly unequal-sided, ovate-oblong to rhomboid-elliptical, more or
less accuminate, sometimes acute, sometimes blunt at the tip;
inflorescences axillary simple or slender panicles, shorter than the
leaves; flowers 4-merous, small, greenish-white, borne on rather long
(3-4 mm), slender, hairy pedicels; petals about 4 mm long; pistil 3-4 mm
long; ovary ovoid, 1.5-2 mm long, 1.1-1.6 wide, not borne on a slender
stipe, 4-locular with small oil glands but no large one at the top of
each locule; style short, cylindrical, 2 mm long, 0.4-0.8 mm wide, tip
truncate, stigma not marked; fruits oblong or fusiform, nearly 2.5 cm
long by 0.8-1 cm wide, drooping, glandular, orange-colored, succulent, 1
seeded.
C. suffruticosa is a remarkable
undershrub that needs further study. It is evidently
deciduous in the Chittagong Hills in northwestern Burma, as the young
leaves and flowers appear together in early spring. The
twigs are often stout, 7 to 8 mm in diameter, with pith 4 to 5 mm in
diameter; the leaf scars of the previous year are heart-shaped, 6 to 7
mm long and 5 to 6 mm broad. Apparently the simple short
stems arise from creeping rootstocks, perhaps because of annual fires
killing the older wood to the ground.
The pistil of this plant when studied in
detail by means of serial microtome sections made by the modified Juel
method (see Swingle, 1939b, p. 270) shows that it differs strikingly from most of the other species of Clausena in
having no well-developed gynophore on which the ovary is borne and no
cells filled with tannin residues scattered through the
tissues. In this latter character, C. suffruticosa resembles C. luxurians,
which does, however, have a definite, though small,
gynophore. It also differs in several other important
characters.
Clausena dentata var. longipes has a pistil resembling that of C. suffruticosa
in general morphology; i.e., it has a poorly developed gynophore and a
rather long style merging gradually with the apex of the
ovary. However, cells containing tannin residues are found
sparingly in the peripheral tissues of the ovary of C. dentata var. longipes and abundantly in the integuments of the ovules.
The fruits of C. suffruticosa,
which were described by Kurz (1877, vol. 1, p. 190) as "oblong,
drooping, nearly an inch long, one-seeded, orange-coloured, succulent,"
are very different from those of any other species of Clausena.
IV. Murraya Koenig
IV. Murraya ("Murraea") Koenig ex Linn. Mant. Pl. 2:554. 1771; nomen conservandum, Regles Intern. ed. 2. 91. 1912. Chalcas L. 1767; Bergera Koen. 1771; Murraya Koen. 1774; Marsana Sonner. 1782.
Type species.—Murraya exotica L. = M. paniculata.
Distribution.—India; Indo-China;
Thailand; southern China: Hainan; Taiwan; Malay Peninsula; Andaman
Islands; Sumatra; Java; Borneo; Philippines; Celebes; New Guinea; New
Caledonia; northeastern Australia.
Common name.—Orange jessamine (or murraya).
Unarmed trees with odd-pinnate leaves
with alternate leaflets; inflorescences, rather large panicles, either
axillary or terminal; flower buds cylindrical or long-ovoid; flowers
rather large, 5-merous; calyx of 5 ovate or lanceolate sepals united at
the base or only in the lower third; petals 5, rather large, lanceolate
or linear, imbricate; stamens 10, free, elongate, filaments flattened in
some species, anthers small, broadly elliptic or oval; disk annular,
cushion-shaped or cylindrical, short; ovary ovoid, with 2-5 locules,
each with 2 (or 1) superimposed or almost collateral ovules; style
rather long and slender, finally falling off, stigma capitate; fruit a
small berry, ovoid or subglobose, with mucilaginous pulp; seeds
medium-sized, with a thin testa, cotyledons plano-convex.
Murraya is a genus containing
eleven species, of which all but three are rather closely related
species that fall into two or three groups not as yet adequately
studied. The only relationship of Murraya that appears clear is with Clausena, a genus that is difficult to distinguish at first sight from Murraya
except by its having, as a rule, much shorter styles and smaller
flowers with larger anthers. Careful study of the genus Clausena has, however, shown that all the species have an hourglass-shaped gynophore of a character not found in Murraya. The tissues of all the flower parts in Clausena
are usually highly impregnated with tannin residues deposited in some
but not all of the cells. The curious species M. alternans, which seems to be related to M. alata, has a stalked ovary unique in Murraya but of different morphology from the gynophore found in Clausena.
The anomalous species M. stenocarpa, having unifoliolate leaves, is still too inadequately known to permit discussion of its relationships.
It is clear that Murraya is not closely related to Citrus; nevertheless Citrus has at least once been successfully grafted on M. paniculata,
a vigorous species easily propagated from cuttings. Dr.
Toxopeus, working in Java (1936, p. 6), reported having crossed Citrus and M. paniculata, but he obtained only stunted hybrids.
Tanaka (1929a) published a monographic study of the species of Murraya (under the genus name Chalcas) which has greatly helped in understanding this genus. He was the first taxonomist to transfer Micromelum glabrum Guill. and Atalantia stenocarpa Drake to the genus Murraya.
A key to the eleven species of Murraya is presented.
1. Murraya paniculata (L.) Jack, Malay. Misc. 1:31. 1820. Chalcas paniculata L. Mant. Pl. 68. 1767; C. camuneng Burm. f. 1768; Murraea exotica L. 1771; Murraya exotica L. 1774; Marsana buxifolia Sonner. 1782; Limonia lucida Forst. 1786; Murraya sumatrana Roxb. 1832; M. odorata Blanco, 1845; M. scandens Hassk. 1866; Chalcas exotica (L.) Millsp. 1895; Murraya banati Elmer, 1915. Illus. Murray, Comment. Soc. Reg. Göttingensis 9:186-91, pl. 1. 1789; Bellenden-Ker, Bot. Reg. 5:pl. 434 (col.). 1819; Hooker, Exot. Fl. 2:pl. 134. 1825; Wight, Icon. Pl. Ind. Or. 1:pl.
96. 1840; Beddome, Fl. Sylv. Anal. Gen. pl. 7, fig. 2. 1871; Penzig,
Studi Bot. Sugli Agrumi, Atl. pl. 17, fig. 15; pl. 18, figs. 12-16.
1887; Guillaumin, in Lecomte, Fl. Gén. Indo-Chine 1:665, fig. 69(5). 1911; and many others (see Stapf, Index Londinensis 4:333 [1930]); fig. 3-7 this work.
Type.—British India. Linn. Herb. London (substitute type not labeled by Linnaeus, fide Jackson, 1912, p, 106).
Distribution.—India, Ceylon,
Burma, Indo-China, China, Taiwan, Malay Peninsula, East Indian
Archipelago, Philippines, Australia, New Caledonia, Melanesian islands.
Common name.—Orange jessamine.
Kurz (1877, vol. 1, p. 190) described
this species as follows: "An evergreen tree, 15-25 ft. [4.6-7.6 m] high,
trunk 6-8 ft. [1.8-2.4 m] high, 1 1/2-2 ft. [46-61 cm] diam., the young
shoots puberulous; leaves unpaired-pinnate or occasionally pinnately
3-foliolate, glossy, glabrous, or sometimes the rachis puberulous;
leaflets alternate, cuneate-obovate or almost obliquely rhomboid,
shortly petioluled, blunt or bluntish acuminate, 1-1 l/2 in. [2.5-3.8
cm] long, coriaceous; flowers rather large, white, in dense but small,
almost sessile terminal corymbs; petals about 1/2-3/4 in. [13-18 mm]
long, recurved; stamens 10, alternately shorter; ovary 2-celled, the
style long with a capitate glandular stigma; berries ovoid-oblong,
bluntish acuminate, nearly 1/2 in. [13 mm] long, orange-coloured,
1-2-seeded; seeds villous."
This species is very widely distributed
and doubtless extremely old. However, it has evolved at a
very slow rate, as is shown by the small morphologic differences that
distinguish it from var. ovatifoliolata (noted below), which has been separated from the other forms of the species for many millions of years ever since Australia lost all land connections
in the Eocene period. The wood of this species—particularly
that of the roots—is much valued by the Malays for making kris handles,
Burkill (1935, vol. 2, p. 1507) noted that the trunks split unless
carefully seasoned and that few pieces are larger than 8 inches (20 cm)
in diameter.
The orange jessamine is a handsome
greenhouse ornamental that blooms profusely. It has large
white fragrant flowers that are succeeded by small red fruits (see fig. 3-7).
In warm subtropical climates it thrives out of doors. It
grows vigorously and can be propagated easily from cuttings.
Citrus cannot as a rule be grafted on it, although one strain of
lemon (an unidentified seedling) made a good growth on it in the
greenhouses of the former Bureau of Plant Industry at Washington,
D.C. There are many varieties and strains of M. paniculata in the Old World; possibly some of them would support Citrus better than the strain now grown in the United States, probably originally introduced from India.
1a. Murraya paniculata var. ovatifoliolata Engl. Die Nat. Pflanzenfam. 3(4):188. 1896. Murraya ovatifoliolata (Engl.) Domin, Bibl. Bot. 89:296. 1927. Illus. Bailey, Compr. Cat. Queensl. Pl. fig. 61 bis. 1909.
Type.—Queensland (F. M. Bailey). Herb. Bot. Gard., Brisbane (?).
Distribution.—Australia: Queensland.
Engler distinguished this variety from
the species as having broadly oval or ovate leaflets. Bailey
(l.c.) described this form as follows: "This, our indigenous form, is
of a more straggling habit with more numerous and larger oil-dots, and
is often decidedly hirsute and tomentose, thus very distinct from the
two Indian ones of our gardens." The leaves are
3-9-foliolate; the twigs, calyx, petals, and ovary hirsute.
The essential oil in the leaves of var. ovatifoliolata from
Queensland was compared with that from the species growing at Dehra
Dunn, India, by Penfold and Simonsen (1925, pp. 146-55). The
oil of both species and the variety was found to consist chiefly of
sesquiterpenes and sesquiterpene alcohols, but "the chief constituent of
the Indian oil was found to be l-cadinene…whilst bisaboline was
similarly identified as one of the sesquiterpenes present in the
Australian oil." The other constituents were not identified
as they did not yield any crystallizable derivatives.
Significant differences were also found in the saponification value of
the two oils. The leaves of the species grown in India
yielded on steam distillation 0.01 per cent of dark-colored oil with a
saponification value of 8.87; leaves of the variety from Queensland
yielded 0.06 to 0.15 per cent of oil having saponification values of
from 19.37 to 26.18. There were also differences in the
rotative power of the oils, that of the species being [a]D-78.2°; that of the variety from -10.2° to -12.2°.
1b. Murraya paniculata var. zollingeri Tan. Jour. Ind. Bot. Soc. 16:232. 1937. Chalcas paniculata var. zollingeri Tan. Bul. Soc. Bot. France 75:709. 1928.
Type.—Bima [or Sumbawa] Island (Zollinger, No. 3351). Herb. Mus. Hist. Nat., Paris.
Distribution.—Central East Indian Archipelago; Bima, Sumbawa, and Timor islands.
Leaflets 3-6, small, chartaceous, margins
much reflexed; rachis thin, declinous, slightly pubescent; fruits not
apiculate, often pendulous, sparsely puberulous.
Tanaka (1929a, p. 27) is uncertain whether this is not the same as M. heptaphylla Spanoghe, in Linnaea 15:178 (1841).
1c. Murraya paniculata var. omphalocarpa (Hay.) Tan. Jour. Soc. Trop. Agr. 1:27. 1929. Murraya omphalocarpa Hay. Icon. Pl. Formos. 3:51. 1913.
Type.—Formosa, Totosho (coll., Kawamakami). Herb. Imp. Univ., Tokyo.
Distribution.—Known only from Taiwan.
Differs from the species in the following
characters: fruits large with attenuate tips, about 21 X 12 mm (when
immature, rostrate, about 15 X 5 mm); flowers larger; petals narrowed at
the base; calyx lobes elongate, ovate to linear-oblong, 3 mm long;
leaflets broad, 5-8 X 4-4.7 cm.
Tanaka (1929a, p. 28) stated that
"these characters may be linked by gradations" with those of the
species, but as the differences are fairly large they can safely be
regarded as varietal but not specific.
2. Murraya gleniei Thwaites ex Oliv. Jour. Linn. Soc. Bot. 5(2):29. 1861. Chalcas gleniei (Thwaites) Tan. Bul. Soc. Bot. France 75:710. 1928. Illus. Trimen, Handbook Fl. Ceylon, Atl. pl. 22. 1893.
Type.—Ceylon (Thwaites, No. 3627). Herb. Kew.
Distribution.—Known only from Ceylon.
This species was best understood by
Trimen (1893, vol. 1, p. 220), who, while he was director of the Botanic
Gardens of Ceylon (where alone the species is found), naturally had
abundant material at his disposal. His description reads: "A
bush, much branched, bark very white, young twigs strongly pubescent;
leaves imparipinnate, 1 1/2-4 in. [3.8-10 cm long]; rachis strongly
pubescent, leaflets 3-7, on short pubescent stalks, upper ones much the
longest, rhomboid-lanceolate, obtuse, emarginate, lower ones rotundate,
all slightly crenate, glabrous; flowers 1/2-3/4 in [13-19 mm] diam.,
about 3-7, in short, racemose, axillary and terminal cymes, pedicels
very pubescent; sepals very small, densely tomentose; petals 1/2 in. [13
mm long]; ovary on a distinct cylindrical stalk, 5-lobed, 5-celled;
berry large, 1 in. [diam.], somewhat pyriform or urn-shaped,
flat-topped, but mammillate in centre, 5-lobed or bluntly 5-angled,
rough with large glands, shining green, 5-celled, the large inflated
cells each containing 1-3 globose green seeds."
This Ceylonese form of the orange
jessamine is much like the normal form of the species except in its
curious inflated star-shaped fruits. It may perhaps be a
mutation which has been able to establish itself as a satellite
species. Engler (1931, p. 320) noted that the ovary is "4-
or 5-locular" and consequently the fruits must be also 4- or 5-lobed.
3. Murraya alternans (Kurz) Swing. Jour. Wash. Acad. Sci. 28:532. 1938. Limonia (?) alternans Wall., in Voigt, Hort. Suburb. Calcut. 139, nomen nudum. 1845; L. alternifolia ("Wall. ap. Voigt") Kurz, Jour. Asiat. Soc. Bengal 42:64. 1873; L. alternans ("Wall.") Hook. f. Fl. Brit. Ind. 1:508, 1875; L. alternans ("Wall.") Kurz, For. Fl. Brit. Burma 192. 1877.
Type.—Burma, Pegu (Kurz, No. 2010). Herb. Kew.
Distribution.—Known only from type
locality. Kurz (1877, vol. 1, p. 192) stated: "Not
unfrequent in the upper mixed and occasionally in the moist forests of
the Pegu Yomah [Mountains, about Lat. 18°40'-19° N., Long. 96°35'-97°
E.], sporadical but usually gregarious."
A slender, simple or sparingly branched
shrub, 60-120 cm [2-4 ft.] tall, with deciduous foliage; twigs slender,
glabrous, with numerous shallow, longitudinal furrows and low ridges;
leaves odd-pinnate, completely glabrous, 11-15 foliolate; leaflets
alternate, nearly sessile, oblong-lanceolate to lanceolate, 2.5-4 cm
long, somewhat unequal-sided toward the cuneately narrowed base,
slightly attenuate to a blunt tip, margins slightly crenate above the
middle; rachis narrowly winged; inflorescences small, short-peduncled,
glabrous, axillary cymes, appearing with the new leaves; flower buds
small, oblong or elliptical, 3-5 X 2-3 mm, flowers short-pedicellate;
calyx nearly flat, 5-lobed, lobes triangular, glabrous, 1-1.5 mm long,
1.5-2 mm wide, with numerous oil glands; petals 5, white, upright,
linear, 5-7 mm long, tapering to a point, with many oil glands in the
upper half; stamens free, filaments 10, slightly swollen above,
sparingly short-pilose, anthers small, oblong, 1.2-1.3 mm long; pistil
glabrous, 4.5-5.5 mm long; ovary borne on a long, slender, nearly
cylindrical stipe, 0.8-1 mm long and 0.4-0.5 mm wide, arising from flat
top of the disk (said to elongate after flowering), the ovary itself
obovate, 1.8-2 mm high, 1.1-1.2 mm wide, bluntly rounded or obcordate at
top because of 2 large oil glands, 1 over each locule; locules 2, each
with 2 ovules suspended from the top; style slender, subclavate, 2.2-2.6
mm long, 0.2-0.5 mm wide, stigma at tip not clearly delimited; disk
annular, as broad or broader than the ovary, 1.8-2 mm wide, 0.5-0.6 mm
high, fruits ovoid, glabrous, short-stalked, about 4 mm long.
This species was assigned, somewhat doubtfully, to Limonia
by Kurz and Sir Jose Hooker, but has apparently never been studied
since the 1870's. It is no longer mentioned in lists of
plants covering Burma, and even the genus Limonia, to which it
was assigned when discovered (and from which it has never been removed),
is no longer in use (see Swingle, 1914-17, pp. 327-28).
This extraordinary plant, frequently
producing only a single slender stem, 2 to 4 feet high, is unique in the
genus Murraya in having deciduous foliage. This species together with Clausena pentaphylla, C. dentata var. dulcis, and C. suffruticosa are
the only members of the tribe Clauseneae having deciduous
foliage. The leaves drop off during the hot, dry season,
which in Pegu begins toward the end of February and lasts until
May. When the summer rains come on, new leaves push out on
the bare stems, and with them clusters of small white flowers appear in
the axils of the leaves.
The type specimen of this species,
collected in Pegu in 1872 by Kurz, was kindly lent to Swingle by Sir
Arthur Hill, director of the Royal Gardens at Kew. A study
of the flower anatomy from serial microtome sections made from this
Herbarium material by the modified Juel method shows clearly that it
belongs in the genus Murraya and is a species near to M. alata,
which occurs not far to the eastward in Indo-China and which also has
leaves with a winged rachis. It differs from all the other
specie of Murraya in having the ovary borne on a slender, nearly cylindrical stipe.
Kurz, in publishing his first description
of this species in 1873, mistakenly used the specific name "alternifolia," although he professed to recognize the specific name "alternans"
first printed (but not adequately published) by Wallich in Voigt in
1845. Hooker corrected this misspelling in 1875 and Kurz
accepted the correction in 1877.
4. Murraya alata Drake, in Morot, Jour. Bot. 6:276. 1892. Chalcas alata (Drake) Tan. Jour. Soc. Trop. Agr. 1:35. 1929.
Type.—French Indo-China, Tonkin, Tan-keuin (Balansa, Nos. 1118, 1119).
Distribution.—North Vietnam: Tonkin (Tan-keuin, Kien-khé, and Bac-bat), Annam.
The brief original description reads, in
translation, as follows: "Shrub, 1 m high. Leaves up to 10
cm long, completely glabrous; petiole and rachis alate; leaflets 7, 3-4
cm long, 1-2 cm wide, oblong or rhomboid, acute or subacute at the tip,
obscurely crenate; petiolule very short and inconspicuously
puberulous. Cymes axillary, 2-3 cm long, few-flowered,
puberulous. Sepals acute. Petals
oblong. Staminate filaments linear. Berry
ovoid."
This description was based on the type
material from Tan-keuin, Tonkin, North Vietnam (Balansa, Nos. 1118,
1119). Guillaumin (1911, p. 659) added a few characters not
mentioned by Drake del Castillo, since he had additional material at his
disposal from Kien-khé and Bac-bat, Tonkin, collected by
Bon. The more important characters first noted by Guillaumin
are described, in translation, as follows: "…Branches glabrous, with
yellow bark. Leaflets 5-7…coriaceous, entire or undulate on
the margins, lateral veins scarcely visible.
Inflorescences…2-3 cm long, branches 15 mm long, pedicels 9 mm
long. Sepals…triangular, acute, 1.5 mm long, pubescent
without. Petals glabrous, erect, obovate, 10-15 mm long,
with parallel veins. Stamens 10, the 5 longest a little
shorter than the petals, and reaching to the stigma; filaments glabrous,
subulate; anthers very small, attached at the base…terminated by a
small grand, not easily visible. Disk annular.
Ovary glabrous, ovoid; style subulate; stigma capitate; locules 2 each
with a single ovule. Fruits red, grouped in corymbs, fleshy,
with 1 or 2 seeds which have a parchment-like testa and a
single-straight embryo with fleshy plano-convex cotyledons."
Like M. alternans, which it
resembles in having leaves with a narrowly winged rachis, this species
is reported as being a shrub only 1 m high. M. alata differs from M. alternans in having persistent instead of deciduous leaves, and flowers with petals about twice as long. The calyx lobes of M. alata are pubescent without and the staminal filaments are glabrous, both conditions being just the opposite of what is found in M. alternans.
4a. Murraya alata var. hainanensis Swing. Jour. Wash. Acad. Sci. 32:26. 1942.
Type.—China, Hainan Island, strand, Haichow (McClure, No. 7611). Herb. Natl. Arbor., Washington, D.C.
Distribution.—China: known only from Hainan Island.
This variety differs from the species
found in Tonkin and Annam in North Vietnam in having the leaflets when
young minutely puberulent on both surfaces and on the
margins. As they mature, the leaflets often become nearly
glabrous, but the petiolules and the rachis remain more or less
pubescent even on mature leaves, and often scattered, short cilia may be
still seen along the margins near the base of mature
leaflets. The calyx lobes are pubescent and the staminal
filaments are glabrous as in the species. The leaflets seem
to be rather more variable in shape (especially in width) than those of
the Indo-Chinese typical form. The fruits are ovoid, about
9-11 X 6-8 mm in herbarium specimens.
This variety is a shrub growing from 1 to
2.5 m high along the beaches, and in the forests of Hainan from sea
level to 1,300 m altitude. The fruits are said by one
collector to be "lustrous deep red" when ripe.
5. Murraya koenigii (L.) Spreng. Syst. Veg. 2:315. 1825. Bergera koenigii L. Mant. Pl. 563. 1771; Murraya foetidissima Teijsm. & Binn. 1864; Chalcas koenigii (L.) Kurz, Jour. Asiat. Soc. Bengal 44(2):132. 1875. Illus. Wight, Icon. Pl. Ind. Or. 1:pl. 13/334. 1838; Guillaumin, in Lecomte, Fl. Gén. Indo-Chine 1:655, fig. 69(4). 1911; figs. 3-8 and 3-9 this work.
Type.—Eastern British India (Koenig, suppl. type). Linn. Herb., London.
Distribution.—Indian peninsula;
northeastern and northwestern India; Ceylon; Burma; North Vietnam; South
Vietnam; Cambodia; Laos; China: Hainan Island, Yunnan, and Kweichow.
Common name.—Curry leaf.
Kurz (1877, vol. 1, p. 190) described
this species as follows: "An evergreen tree, 15-20 ft. [4.6-6.1 m] high,
trunk 4-10 ft. [1.2-3 m] high, 1/2-1 1/2 ft. [15-46 cm] in circum.,
glabrous or slightly puberulous; leaves unpaired-pinnate, the rachis
usually more or less pubescent, rarely quite glabrous; leaflets in 5-10
pairs with an odd one, on a short puberulous petiolule,
oblong-lanceolate or ovate, almost falcate, oblique at base, about 1-1
1/2 in. [2.5-3.8 cm] long, acuminate, more or less serrulate,
membranous, glabrous, except on the midrib, which is often puberulous;
flowers small, white, in terminal corymbs; petals oblong-lanceolate,
acute, about 2-3 lin. [4-6 mm] long; stamens 10, alternately shorter;
ovary 2-celled, the style short and thick; berries oblong, somewhat
acute, the size of a small pea, l-2-seeded, bluish-black."
This species was said by Trimen (1893,
vol. 1, p. 219) to be "extremely like the small-leaved form of Micromelum pubescens [= M. ceylanicum],
from which it may be distinguished by its more numerous more pubescent
and small leaflets, and more compact corymbose terminal
inflorescence." The pistil is much shorter than the stamens.
Dr. David Fairchild reported (Bur. Pl.
Ind., Inventory 88, No. 68351) that "the fresh leaves form a constant
ingredient of the Ceylonese curries and give them a very agreeable
flavor." He stated further (1930, p. 284) that the fresh
leaves of this species are "deemed essential to all the curries of
Ceylon." They are "boiled with the curry but thrown out of
it before serving." Dr. Fairchild had a fine fruiting tree
of M. koenigii growing in his tropical garden, "The Kampong," at
Coconut Grove, Florida, where it was one of the most prized of his
collection of citrus fruits and their wild relatives (see fig. 3-8). He regularly used the fresh leaves in making curry.
Trimen stated (1893, vol. 1, p. 221):
"This is the familiar 'curry-leaf,' a constant ingredient in curries and
mulligatawny." He reported the species as rather rare in
the wild state in Ceylon but "very much cultivated," doubtless for use
in curries.
Dr. David Fairchild obtained seeds of
this species in 1926 in Ceylon. Plants grown from this seed
have thrived on the peculiar soil (a very sandy loam intermixed with
porous limestone fragments of rock that often occupy half or more of the
bulk of the soil) found in Miami and vicinity in the extreme
southeastern part of Florida.
6. Murraya microphylla (Merr. & Chun) Swing. Jour. Wash. Acad. Sci. 32:26. 1942. Clausena microphylla Merr. & Chun, Sunyatsenia 2:251. 1935. Illus. Merrill & Chun, loc. cit. fig. 27. 1935.
Type.—China, Hainan Island, Sunchuen (Chun and Tso, No. 43323). Herb. Arnold Arbor., Harv. Univ., Cambridge.
Distribution.—China: known only from Hainan Island.
Common name.—Small-leaved murraya.
The original description by Merrill and
Chun reads, condensed and translated, as follows: "A shrub or small
tree, branches glabrous, branchlets with a dispersed white
pubescence;…leaves imparipinnate…5-7 cm long, petiole and rachis with
scattered white pubescence of short curved hairs; leaflets, 5-10 on each
side, alternate or subopposite…oblong or oblong-ovate or
oblong-lanceolate, upper ones usually larger up to 2 cm long…lower ones
subopposite, 3-4 mm diam.; intermediate ones 5-18 mm long, 3-6 mm wide,
all of them crenulate, obtuse…base usually inequilateral; lateral veins
3-6 pairs…inflorescences terminal, sparingly
pubescent…short-pedunculate, 2-2.5 cm long and wide; [flowers unknown];
fruits few, ellipsoid or ovoid-ellipsoid, up to 1 cm long, glabrous,
glandular-punctate…persistent sepals 5, oblong-ovate, punctate,
glabrous, obtuse or subacute, 1 mm long; pedicels scatteringly
pubescent, 2-2.5 mm long."
A specimen collected by C. Wang (No.
32740), July 4, 1933, on the Fourth Hainan Expedition of Sun Yatsen
University (in Herb. Arnold Arbor.) has good flower buds, 4-5 X 2.5 mm:
petals show scattered, very dark oil glands. Serial
microtome sections show the pistil to be 4 mm long, disk very short and
not delimited from the ovary, which is 1.2-1.5 mm long and 0.9-1 mm
wide, with 1 or 2 locules, with 1 or 2 large oil glands at the top of
the locule (not in a locular process), merging into the broad style,
about 3 X 0.4-0.5 mm, slightly swollen at the top into a subcapitate
stigma, 0.7-0.9 mm diam., which shows a few small oil
glands. The tips of the petals also show several fairly
large oil glands. The stamens are about as long as the
pistil, with linear subulate filaments.
The finding of flowers of this interesting plant shows clearly that it is a species of the genus Murraya,
of which it is a striking member, very different from any other species
because of its small leaves and tiny leaflets. The
collector's notes on the Hainan specimens show that it may reach 6 m in
height, and have a trunk diameter of 15 cm. It bears white
fragrant flowers.
7. Murraya siamensis Craib, Kew Bul. Misc. Inform. 1926(8):340. 1926. Chalcas siamensis (Craib) Tan. Bul. Soc. Bot. France 75:710. 1928.
Type.—Thailand, Lampang, Mê Kat, alt. 250 m (Winit, No. 849). Herb. Kew.
Distribution.—Thailand. Reported from four administrative districts by Craib (1926, vol. 1, p. 230).
Craib’s original description, translated,
reads as follows: "Small tree, trunk with fuscous bark having high
ridges (fide Winit); young twigs with curly pubescence, year-old
twigs puberulous, then fuscous, with small lenticels. Leaves
15-24 cm long (including the petiole, 1-2.5 cm long), petiole and
rachis almost terete with dense curly pubescence; leaflets 17-25,
alternate or rarely subopposite, inequilateral (one half oblanceolate or
lanceolate, narrowed at the base; the other half ovate, subtruncate at
the base), apex obtuse, subacuminate, 2-7 cm long, 1-2.7 cm broad,
chartaceous, above curly pubescent, very soon more or less glabrescent
below, chiefly pubescent at the midrib, lateral veins 5-7 pairs,
anastomosing near the margin above, later conspicuous, somewhat
prominent below, veinlets somewhat conspicuous above, below forming a
delicate rather prominent reticulation, margin subentire or more or less
obscurely crenulate, petiolule about 2 mm long, covered with dense,
curly pubescence. Panicles terminal, subcorymbose, 15 cm
long; pedicels 3-4 mm long with short curly pubescence.
Sepals 5, ovate, lanceolate or deltoid, obtuse, 1.25 mm long, covered
with short, curly pubescence without. Petals 5,
linear-oblanceolate, incurving-apiculate, 6.5 mm long, 1.75 mm wide,
glabrous, thickened at the middle, imbricate. Disk fleshy,
glabrous, slightly shorter than the calyx. Stamens 10,
alternate ones longer, filaments 4-5 mm long, narrowed toward the apex,
the lower half slightly broader but scarcely complanate, anthers about 1
mm long, papillate. Ovary slightly oblong, scarcely 1.5 mm
long, glabrous, shortly stipitate; style 3-5 mm long, articulated at the
base, glabrous, stigma capitate. Fruit (immature), 1 cm
diam."
Tanaka (1929a, p. 34) gave a
redescription of the material cited by Craib which adds a few points to
Craib's diagnosis. The leaves are clearly dotted on the
upper surface; the terminal inflorescence is small, bearing 10-15
flowers; "flower buds small, oblong-ovoid, about 5 mm long, without
glandular dots, pedicels short, about 6 mm, densely pubescent…ovary
cylindric, notched, continuous with the cylindric style."
Tanaka reported that the fruit clusters are as much as 9 cm wide; the
fruits are large, "black, somewhat 4-angled, indistinctly divided by
shallow longitudinal grooves"; oil-dots large, more or less indistinct,
pustulate; calyx lobes persistent, with long soft hairs; "pedicel about
1.5 cm long, continuous to branch of peduncle…about 2 cm
long." He found that the fruits, usually about 1.5 cm diam.
may attain 2 cm, and the fresh fruit may measure still more.
Tanaka (1929a, p. 34) stated: "This species is closely allied with C. [Murraya] koenigii,
but dots on the petals are nearly indistinct, filaments are less
subulate, petals much narrower, and fruit much larger and
4-grooved. The pubescence of the plant is more pronounced
than C. [Murraya] koenigii, and sometimes the whole
plant is covered with white curved hairs, even…the upper surface of the
leaflets." Winit noted on his label on the type specimen
that the plant is decidedly shrubby, blackish with deeply cracked bark,
and has greenish-white, scented flowers.
A specimen from Thailand, collected on
December 31, 1928, by Dr. A. F. G. Kerr (No. 9740) has apparently
mature, globose, or slightly depressed-globose fruits, about 1.5 to 1.7
cm in diameter in the dry state, that do not show any distinct
longitudinal grooves but merely very broad, very shallow depressions
between the slightly protuberant locules.
8. Murraya euchrestifolia Hayata, Icon. Pl. Formos. 6:11. 1916. Clausena euchrestifolia (Hay.) Kanehira, Formos. Trees 97. 1917; Chalcas euchrestifolia (Hay.) Tan. Jour. Soc. Trop. Agr. 1:32. 1929. Illus. Kanehira, Formos. Trees 104. 1917, and ibid. rev. ed. 309, fig. 263. 1936.
Type.—Formosa, Nantôchô, (T. Itô). Herb. Imp. Univ., Tokyo.
Distribution.—Taiwan.
Tanaka (1929a, p. 32) described
this species as follows: "Shrub; leaflets up to 8, rachis fine,
puberulent; leaflets elliptic, acuminate at both ends, shiny above,
largest 9.5 X 3.4 cm, nearly glabrous, lower surface of the midrib
slightly puberulent, margin entire. Inflorescence [a]
terminal, many-flowered cyme, buds small, about 4 X 1.4 mm, black
dotting few on the upper half. Calyx well lobed, about 1.5
mm diam., lobes triangular, black, glabrous down to the base, margin not
pilose; pedicel slender, 4-5 mm long, pilose with soft, golden, curved
pubescence. Petals 5, oblong-oboval, about 4.5 X 1.5 mm,
obtuse at the apex, not much narrowed at the base, with approximately 10
dots on outside. Stamens 10, one shorter after the other,
[longer and shorter ones alternating], longer ones about 4.5 mm, nearly
as long as the petals when fully expanded, filaments linear, flat,
gradually narrowed and acutely pointed; anther small, roundish, slightly
cordate, about 2-3 mm diam. Pistil slightly shorter than
the stamen; ovary oval, constricted at the base toward the broad end;
style cylindric, terete, often slightly curved, stigma obscure,
altogether about 3.5 mm long. Berry globose, not apiculate,
largest about 1 cm across, smooth, rather sparingly large
pellucid-dotted, dark colored."
Tanaka (1929a, p. 32) stated that this plant most closely resembles M. crenulata in
appearance, but the calyx lobes are acutely triangular, and the
leaflets are not so oblique, lacking crenulation. In this
respect, it approaches M. koenigii more closely, although the
number of leaflets is fewer and they are larger and
glabrous. It differs from both species in having a smaller
flower, an obscure stigma, and a slightly constricted ovary.
9. Murraya crenulata (Turcz.) Oliv. Jour. Linn. Soc. Bot. 5(2):29. 1861. Glycosmis crenulata Turcz. Bull. Soc. Nat. Mosc. 31:250. 1858; Micromelum coriaceum Seem. 1865; Clausena worcesteri Merr. 1910; C. citriodora Merr. 1925.
Type.—Philippines (Cuming, No. 335). Herb., Leningrad.
Distribution.—Java, Philippines, Celebes, New Caledonia.
Tanaka (1929a, p. 30) described
this species as follows: "Shrub; leaves pinnate, composed of about
6-7-paired leaflets; leaflets medium-sized [3-6 X 1-2 or 3 cm], much
oblique, oval or oboval, acuminate or mucronate at the apex with blunt
tip, acute at the base (roundish in the lower leaflets), very short
petiolulate, veins very distinct, irregular, margin more or less
crenulate, semicoriaceous, shining above, drying black, and midrib
always glabrous. Inflorescence a terminal cyme,
many-flowered; flower small, but cylindric, about 5 X 2 mm, apex
rounded; petal narrow, striated, with obscure black dots.
Calyx cupulate, puberulent, lobes broad and rounded, side often
imbricate and ciliate on margin; peduncle slender,
tomentose. Stamens free, unequal in length, filaments long,
linear, more or less dilated at the lower half, very sharp pointed at
the apex, anther globose. Pistil nearly as long as the
filaments; ovary ellipsoid, apex not narrowed, rather broad and more or
less ridged, base somewhat narrowed to a cylindric disk; style long,
terete, cylindric, stigma globose. Berry nearly globose and
minutely apiculate, dark-colored."
Tanaka noted that M. crenulata is allied to M. koenigii but
differs from it in having fewer leaflets, which are thicker, larger,
and attached to a glabrous instead of a pubescent rachis.
The fruit is subglobose and minutely apiculate, whereas in M. koenigii it is short-ellipsoid and apiculate. M. crenulata is often confused in the field with Clausena anisum-olens and with Micromelum minutum var. curranii, but it has long flower buds and long pistils, which are never found in Clausena or Micromelum.
SPECIES OF UNCERTAIN RELATIONSHIPS
10. Murraya glabra (Guill.) Swing. Jour. Wash. Acad. Sci. 28:532. 1938. Micromelum glabrum Guill. in Lecomte, Not. Syst. 1:216. 1910; Chalcas glabra (Guill.) Tan. 1929. Illus. Guillaumin, in Lecomte, Fl. Gén. Indo-Chine 1:646, fig. 68(11-12). 1911.
Type.—French Indo-China, Kien-khé, Tonkin (Bon, No. 2977). Herb. Mus. Hist. Nat., Paris.
Distribution.—Vietnam: Tonkin and Annam.
Guillaumin (1911, p. 650) described this
species as follows: "Small shrub, 1 m high. Branches
entirely glabrous, with very odorous oil glands. Leaves
12-46 cm long; leaflets 3-9, alternate, glabrous, obovate or
oblong-lanceolate, 5-17 X 2-9 cm, inequilateral and pointed at the base,
abruptly acuminate at the tip, very slightly denticulate; lateral
veins, 6-9 pairs, prominent on lower surface; petiolules cylindric,
glabrous, 3-4 mm long; petiole cylindric, glabrous,
glandular. Inflorescences shorter than the leaves, with very
short pubescence; pedicels longer than the flowers, with 2 small bracts
at the base or lower third; flower [buds] 4 mm long, white.
Calyx of 4 connate, indistinct, very shortly ciliate
sepals. Petals 4, length 6 mm, glabrous,
lanceolate. Stamens 8, of which 4 are longer; filaments
dilated and pubescent above; anthers attached by the back, oval, with a
few hairs. Disk extremely short. Ovary
cylindric, warty, glabrous; style longer than the ovary, ending in a
globose stigma."
Tanaka (1929a, p. 36) in his monograph of the genus Chalcas (= Murraya)
made a few additions and changes to Guillaumin's description, among
others the following: "Leaflets 3-11, generally 5…texture thin,
chartaceous…Rachis rather thin [slender?], about 28 cm long…Flower bud
about 6 X 2.5 cm. Ovary…distinctly constricted at about
one-third from the apex…"
This anomalous species was described as " belonging to Micromelum but was transferred to Murraya by
Tanaka "on account of having a large cyme, long flower buds with
prominent dots and elongated style." The specimens from
Annam have, so Tanaka found, distinctly terminal inflorescences which
bear nearly 100 flowers. The fruit is unknown.
11. Murraya stenocarpa (Drake) Swing. Jour. Wash. Acad. Sci. 28:532. 1938. Atalantia stenocarpa Drake, in Morot, Jour. Bot. 6:277. 1892; Glycosmis stenocarpa (Drake) Guill. 1912; G. bonii Guill. 1910; Chalcas stenocarpa (Drake) Tan. Bul. Soc. Bot. France 75:711. 1928. Illus., Guillaumin, in Lecomte, Fl. Gén. Indo-Chine 1:667, fig. 71(3-6). 1911.
Type.—French Indo-China, Tonkin (Balansa, No. 1110). Herb. Mus. Hist. Nat., Paris.
Distribution.—North Vietnam: Tonkin.
The original description of Atalantia stenocarpa by
Drake del Castillo may be translated as follows: "Small tree (up to 1 m
high), spineless, very glabrous; leaves subcoriaceous, shining,
elliptical or oblong-lanceolate (leaf blades up to 15 cm long, 6 cm
wide; petiole about 4 cm long), acute at the base, narrowed at the apex,
obtuse or subemarginate, serrate. Cymes axillary,
few-flowered. Flowers small. Calyx lobes 5,
short, ovate, acute. Petals oblong. Stamen
filaments free, ciliate. Ovary oblong, substipitate, with 2
ovules. Fruit oblong, shortly attenuate at the apex."
A redescription by Guillaumin (1911, p. 671) under the name Atalantia stenocarpa added
a few details "…Leaflets 4-12.5 X 3-5 cm, cuneiform at the base,
attenuate and slightly emarginate at the tip; with 9-10 pairs of lateral
veins, clearly distinct from the veinlets and like them elevated above
the surface below; oil glands easily visible principally on the margins
and in the angles of the teeth; petiole 2-3.5 cm, with a swelling at the
base of the leaf blade; ovary ovoid, borne on a low disk, with 2
locules, each with 1 ovule; style cylindric-pubescent.
Fruits fleshy, reddish, oblong, 15 mm long, attenuated at the tip."
This anomalous species, with unifoliolate
leaves, was placed in this genus by Tanaka, although originally it was
placed in the genus Atalantia. Guillaumin, because of this leaf-character, transferred the species to Glycosmis, but, according to Tanaka, "the plant lacks ferruginous pubescence characteristic to Glycosmis…The ovary…is glandular and somewhat stalked at the base and this character agrees with Clausena and not…Atalantia. The filaments of Clausena,
however, are very much attenuated, ending with a filiform tip, and the
anther is extremely long. In the present species, the
filaments are dilated [at the base] and abruptly pointed [at the tip]
and the anthers are not large; moreover they are pubescent, and [have]
pellucid dots on the surface of the petals and calyx lobes similar to Murraya glabra."
Tanaka (1928b, p. 711) emphasized the "exact coincidence of the characters of the stamens in the present species" with those of M. glabra. However, M. glabra is itself a somewhat anomalous species of Murraya, and both of these species should be studied more fully.
Subtribe 3. Merrilliinae: Large-Fruited Remote Citroid Fruit Trees
The subtribe Merrilliinae contains only one genus with a single species, Merrillia caloxylon native to the Malay Peninsula and to the adjacent coast of Sumatra. Merrillia differs widely from all the other genera of the tribe Clauseneae and has a superficial similarity with the genus Swinglea, one of the aberrant Hard-Shelled Citroid Fruit Trees belonging to the tribe Citreae.
Swingle follows Engler (1931, p. 211) in placing Merrillia next to the genus Murraya,
which it resembles in general aspect and in its hard handsome wood,
although differing greatly in flower and fruit characters.
The flowers are the largest known in the orange subfamily but do not
open fully (as do those of Citrus). They are
trumpet-shaped, becoming completely pendent during anthesis, with only
the upper third of the petals recurved. The petals composing
the corolla are not only the largest known in the orange subfamily, but
they are also slightly unequal in size and shape, i.e., slightly
zygomorphic. The fruits are as strange as the flowers and
have a thick, radially lacunose, leathery exocarp and seeds covered with
abundant, narrow, flattened somewhat deeply laciniate paleae,
characters not found elsewhere in the subfamily.
This subtribe seems to have been derived as an offshoot from the ancestors of Murraya that evolved rapidly in flower and fruit characters while retaining the general facies of a Murraya of the M. paniculata group of species.
V. Merrillia Swing.
V. Merrillia Swing. Phil. Jour. Sci. Bot. 13:337. 1918.
Type species.—Murraya caloxylon Ridl. = Merrillia caloxylon (Ridl.) Swing.
Distribution.—Malay Peninsula: southern Thailand, upper Perak; northeastern Sumatra. Cultivated in Singapore Botanic Gardens.
Common name.—Merrillia.
Swingle's original description, translated, reads as follows: "Genus allied to Chaetospermum [now Swinglea]…from
which it differs chiefly in the 5-6-locular ovary having an irregular
lacunose pericarp; the seeds densely scaly, scales elongate,
membranaceous, slightly laciniate; the leaves sessile, pinnate, the
rachis narrowly winged, and the leaflets alternate.
"Unarmed tree; leaves pinnate, sessile or
subsessile; rachis narrowly winged; leaflets alternate, lower ones
small, the next higher ones gradually increasing in size, the terminal
ones largest; petiolule very short; inflorescence axillary,
2-1-flowered; flowers perfect, rather large, 5-merous; calyx 5-merous,
small, lobes triangular-ovate; petals 5, narrow; stamens 10, free,
unequal; ovary 5- (rarely 6-) locular, stipitate, merging into the
elongate style, stigma capitate, ovules 8 to 10 in each locule; fruit
subglobose, large pericarp very thick, coriaceous, irregularly lacunose
with cartilaginous walls, segments filled with mucilaginous gum, seeds
numerous in each segment (8-10), lenticular, densely scaly, scales
slightly fimbriate, membranaceous, elongate, hilum carinate,
subariloid. Cotyledons hypogeous in germination, first
leaves simple, opposite, broadly ovate-lanceolate."
The very long, trumpet-shaped, slightly zygomorphic flowers of Merrillia,
often 55 to 60 mm long, are unique in the orange subfamily.
The large fruit with its thick, radially lacunose epicarp and seeds
covered with flat, narrow, laciniate paleae are equally
strange. These and other remarkable flower and fruit
characters of Merrillia constitute one of the most striking
examples of rapid divergent evolution to be found among the many that
are seen in the orange subfamily, such as the highly xerophytic Eremocitrus and the anomalous Monanthocitrus with its horned fruits and spotted seeds. The extraordinary fact is that Merrillia not
only has flowers, fruits, and seeds which differ very widely from those
of the other genera of the tribe Clauseneae, but fruit characters
analogous to those of the genus Swinglea, an aberrant member of the Hard-Shelled Citroid Fruit Trees belonging to another tribe.
When Swingle described Merrillia as a genus in 1918, he thought that it probably belonged with Swinglea in
a special group of the subtribe Balsamocitrinae, although he directed
attention to the unusual characters that make it "perhaps the most
aberrant of the citrus fruits." Swingle had the good fortune
to be able for several consecutive years to study in minute detail the
leaf and flower morphology of a healthy, everbloomingtree of this plant
growing in the citrus greenhouse of the former Bureau of Plant
Industry. As a result of these studies Swingle considered Merrillia to be a very anomalous member of the tribe Clauseneae that has probably evolved from a Murraya-like ancestral form.
Merrillia caloxylon (Ridl.) Swing. Phil. Jour. Sci. Bot. 13:338. 1918. Murraya caloxylon Ridl. Jour. Straits Branch Roy. Asiat. Soc. 50:113-14. 1908. Illus. Swingle, loc. cit. pls. 5, 6; Foxworthy, Malay. For. Rec. 3:169, unnumbered fig. 1927; fig. 3-10 this work.
Type.—Upper Perak, Kenering, at 500 ft. elevation (Robinson, No. 5548). Herb. Brit. Mus., London.
Distribution.—Malay Peninsula:
southern Thailand, Patani Province; Federation of Malaysia: Kedah,
Perak, Selangor, Pahang; northern Sumatra: Asahan.
Common name.—Flowering merrillia (or ketengah).
The original description of this species
(Ridley, l.c.) follows: "A tree of considerable size, the branches
covered with a pale flaky bark. Leaves 8 inches [20.3 cm] or
more long, with 13 leaflets; rachis flattened and winged, narrow;
leaflets 3-3 1/2 inches [7.6-8.8 cm] long or less by 1 1/2 inches wide
[3.8 cm], alternate, oblanceolate, obtusely acuminate with a triangular
base, minutely petiolate, inequilateral, thin, bright deep
green. Flowers pale yellowish-green, several together in
small panicles, in the upper axils of a branch, about an inch [2.5 cm]
long. Sepals connate, ovate-acute, 1/10 inch [2.5 mm]
long. Petals and stamens not seen. Ovary
stalked, hairy, style rather stout, hairy, stigma
capitulate. Fruit oblong, rounded at both ends, 4 inches
[10.2 cm] long and three inches [7.6 cm] in diameter, the pericarp
dotted and warty, greenish, eventually becoming yellow, half an inch
[12.7 mm] thick, lemon yellow inside, full of long resin cells narrowed
at the mouth and dilated below, cells 5, with rather thick tough walls,
pulp of transparent flattened sticky fibers, olive green in colour and
tasteless. Seeds numerous, about 5 in a section,
ovate-flattened, half an inch [12.7 mm] long, 1/8 inch [3 mm] thick,
olive gray."
Open flowers of this species were not
seen by Ridley. As Swingle reported in the original
description of Merrillia, petals from flowers of a tree in the
Singapore Botanic Gardens grown from seed from Patani Province, in
extreme southern Thailand, were "35-40 X 5-10 mm, bluntly pointed at the
apex and narrowed gradually to the base." A small tree
grown in the citrus greenhouse at Washington, from seeds of this tree in
the Singapore Botanic Gardens, bore flowers that were even larger,
having petals 4.5-5.5 cm long and 8-11 mm wide. The flowers
were pendent and never opened fully, having the imbricate petals curving
outward at the tips and making a trumpet-shaped flower, greenish-white
on the outside and white within. No other species of the
orange sub-family has flowers of this type. Swingle directed
attention (1918, p. 339, pl. 5) to the curious pair of nearly opposite,
small, broad, and often suborbicular leaflets which are borne very near
the base of the rachis, much nearer than in any other pinnate-leaved
species in the orange subfamily (fig. 3-10).
This remarkable species, called ketenggah in the Malay Peninsula, resembles Murraya paniculata
in its general habit of growth and in its leaves, and even in the
texture and color of its wood. These two species are
sometimes confused by the natives under the name kemuning, which properly applies to Murraya paniculata. The flowers of Merrillia are entirely different, and its fruits are still more unlike those of Murraya, so it stands out taxonomically as a strikingly different plant obviously belonging to a distinct genus.
This tree well deserves to be grown in
greenhouses or out of doors in warm subtropical climates as an
ornamental. When a small tree, 3 to 3.5 m high, it flowers
abundantly at frequent intervals, almost all the year round.
Its curious, pendent, trumpet-shaped flowers, although not
conspicuously colored, are attractive because they are produced in such
abundance and are pleasantly fragrant.
In his notes following the original description of Murraya caloxylon Ridley
stated that it "is famous in the Malay Peninsula for its beautiful
wood," which "is of a bright yellow color ornamented with dark brown
streaks and stains, fairly hard in texture and taking a good
polish." It is said to be highly prized by the Malayans for
making walking sticks, kris handles, and other small
objects. A British official made beautiful furniture, boxes,
etc., out of the wood. Foxworthy (1927, p. 170) considered
it a slow-growing species and thought that it would require about thirty
years to reach commercial size. It is so rare in the wild
state that any considerable supply of wood would have to come from
cultivated plants.
This species, or one very closely related
to it, has been found in northeastern Sumatra directly across the
Malacca Strait from its habitat in the Malay Peninsula. Mr.
B. A. Krukoff, in November-December, 1932, collected good fruiting
material of this tree "in primary forests on ‘red’ soil" at Hoeta
Padang, near Asahan, northeastern Sumatra (Krukoff, No. 4319, in Herb.
Arnold Arbor.). Krukoff noted on the label "tree 110 ft.
[33.6 m] high," i.e., nearly twice the height yet reported for M. caloxylon growing
in the Malay Peninsula! An earlier collection made at the
same place in December, 1930, by Krukoff was from a small tree only 15
cm in diameter. Mr. C. G. G. J. van Steenis collected in
1932 a leafy branch of Merrillia at 120 m altitude on Mount
Maligas, Simeloengoen, eastern Sumatra (van Steenis, No. b.b. 20415, in
Herb. Arnold Arbor.). No other tree in the orange subfamily
has been found to attain the height reported by Krukoff. If
such giant trees produce wood as beautiful as the smaller form growing
in the Malay Peninsula, it would be worth while to test them under
cultivation.
TRIBE II. CITREAE: CITRUS AND CITROID FRUIT TREES
The tribe Citreae includes Citrus and all of its near relatives as well as many more remote relatives that have not yet been hybridized with Citrus or grafted on it. The Citreae may be described as follows:
Small trees or woody, clambering lianas
almost always with single or paired axillary spines at the nodes of the
twigs; leaves persistent (except in three monotypic genera, Poncirus, Aegle, and Feronia), usually simple or 1-3-foliolate (usually pinnately 3-foliolate with a short petiole and the middle leaf larger, but in Luvunga
palmately 3-foliolate with a very long petiole) or sometimes
odd-pinnate with strictly opposite pinnae; petioles often winged;
flowers in axillary clusters, or in terminal or axillary panicles or
corymbs; flowers white or greenish, usually fragrant; calyx with 3-5
sepals or lobes; corolla imbricate in aestivation, with 3-5 (rarely 6)
petals; stamens 2-4 or more times as many as the petals; ovary
2-18-locular, ovules 1-18 (usually 1-12) in each locule (22 or more in Burkillanthus);
fruits usually orange- or lemon-like in external appearance, often
small, sometimes small red or nearly black juicy berries; in the
subtribe Citrinae the locules contain pulp-vesicles filled with juice
but in the other two subtribes (Triphasiinae and Balsamocitrinae) the
locules lack pulp-vesicles, but are usually filled with a mucilaginous
gum; seeds with one or several embryos; if with several, only one
(rarely two) is a true embryos, the others being false embryos that
develop from nucellar buds that grow into the embryo sac; germination
hypogeous or epigeous.
Almost all the species develop single or
paired spines in the axils of the leaves of vigorous shoots, especially
on young trees. The leaves are simple, unifoliolate, or
trifoliolate in most of the genera, but a few genera, Hesperethusa, Feroniella, and most of the species of Citropsis have
odd-pinnate leaves with the leaflets attached to the rachis in strictly
opposite pairs (very different from the alternately attached leaflets
of the tribe Clauseneae). Such odd-pinnate leaves often have
the petioles and the segments of the rachis between the pairs of
leaflets broadly winged. The rachis is articulated at the
point of attachment of each pair of pinnae and these articulated
segments fall apart when the leaf finally falls off. The
leaves of Luvunga are palmately trifoliolate with very long
petioles and pulvini at the bases of the petiolules and of the
petioles. Three genera, Poncirus, Aegle, and Feronia,
have deciduous leaves; all the other genera have persistent (evergreen)
leaves. The species with trifoliolate and unifoliolate
leaves usually have winged petioles, whereas the species with simple
leaves usually have wingless petioles, although the margins of the leaf
blade are sometimes decurrent on the petiole, for part of its
length. The ovary has 2 to 18 or 20 locules, each with 1 to
18 ovules (22 or more in Burkillanthus) in each locule. The ovaries with 2 to 5 locules usually have one or two ovules in each locule (except in Burkillanthus);
those with 6 to 18 locules usually have 4 to 16 or even 18 ovules in
each locule. The fruits are often small, but they are large
or very large in Citrus and in Burkillanthus and in several of the genera of the subtribe Balsamocitrinae.
In the course of an investigation of the
vascular traces of all obtainable genera of the orange subfamily,
Tillson (1938, pp. 12, 25; Tillson and Bamford, 1938, pp. 785, 789, 791)
found that most of the genera of the tribe Citreae studied (21 out of
24) showed fusion of the bundles which arise from the axis and extend to
the sepals and petals; "the sepal midribs carry out the lateral petal
bundles fused to them, and in some species the lateral sepal bundles are
fused in varying degrees to the petal midribs." The three closely related genera Aegle, Afraegle, and Aeglopsis
are without fusions of either kind. None of the many
species belonging to the five genera of the tribe Clauseneae showed
fusions of sepal and petal bundles.
The tribe Citreae is distributed in
southeastern Asia and the Monsoon region to the southeast as far as
eastern Australia, New Caledonia, New Guinea, and the Melanesian
islands; also in tropical (and subtropical) mountainous regions in
eastern, central, and western Africa.
The tribe Citreae contains, as here
treated, twenty-eight genera with 124 species, which fall very naturally
into three subtribes. A key to the subtribes of Citreae is presented.
Subtribe 1. Triphasiinae: Minor Citroid Fruit Trees
Small trees or woody climbers, usually
with single or paired spines in the axils of the leaves, but often
spineless; leaves pinnately 3-foliolate (palmately 3-foliolate in Luvunga),
often 1-foliolate or even simple; fruits small, often orange- or
lemon-like in appearance, rarely small red or black juicy berries; fruit
locules without pulp-vesicles, but usually filled with mucilaginous
gum; ovary subsessile or more or less stalked, borne on a disk or on a
longer cylindrical gynophore with 2-5 (rarely 1) or even 6 or 7 locules,
and 1-6 or 8 ovules in each locule; fruits with gland-dotted peel,
sometimes soft and berry-like, usually firm and often resembling
miniature oranges or lemons but always lacking pulp-vesicles.
Most of the eight genera of the subtribe
Triphasiinae contain species with one or two axillary
spines. However, all four species of the genus Oxanthera are thornless and Wenzelia
has six thornless species (also two with single spines and one with
paired spines). All the species of this subtribe have
persistent evergreen leaves but they vary greatly in the different
genera: Wenzelia, Monanthocitrus, Merope, and Pamburus have simple leaves with very short, wingless, non-articulated petioles; Triphasia has pinnately trifoliolate or simple leaves; Luvunga
has palmately trifoliolate leaves with the leaflets attached by
pulvinoid petiolules to a long petiole with a pulvinus at the base; Paramignya
has unifoliolate leaves with wingless petioles usually pulvinoid at the
junction with the blade (the two last-named genera have petioles
articulated with the leaf blade); Oxanthera has three species
with unifoliolate leaves with articulated petioles and one simple-leaved
species with nonarticulated petioles.
The eight genera of this subtribe are all
native to an area partly superimposed on that in which the True Citrus
Fruit Trees occur, but this area, instead of being barrel-shaped, is
rather a long, obtuse-angled triangle with its acute apex cut off,
having a land base in Asia extending about 4,600 kilometers from western
India to southeastern China and Hainan Island and reaching some 10,000
to 11,000 kilometers to the southeast into Polynesia. This
area falls mostly in the Monsoon region. Its middle portion
is about 3,000 kilometers wide from Sumatra to the Philippines and its
blunted southeastern apex, which is bounded by New Caledonia and the
Fiji Islands, is about 1,800 kilometers wide.
Of the eight genera included in this subtribe, only two, Oxanthera and Monanthocitrus, have a very restricted range, Oxanthera being found only at the very point of the triangle, in New Caledonia (and near-by Art Island), and Monanthocitrus in west-central New Guinea. Merope (which has leaves and petioles resembling Wenzelia)
occurs in brackish coastal swamps from northwestern New Guinea and
Amboyna Island to the southwestern Philippines, Java, Malay Peninsula,
Burma, and Bengal. Wenzelia, Merope, and Monanthocitrus
all include New Guinea in their range and may possibly have originated
there. These three genera and the related genus Oxanthera
are the only ones in the subtribe with more than two (4 to 8) ovules in
each locule. The other four genera (all with one or two
ovules in each locule) seem to have originated in southeastern Asia and
to have spread a greater or less distance into the East Indian
Archipelago: Triphasia and Luvunga range clear through to New Guinea; Paramignya ranges to Sumatra and the Philippines; whereas Pamburus has spread only as far as Sumatra, Java, and Borneo.
The subtribe Triphasiinae contains three
fairly distinct groups of genera, although most of the genera included
differ strikingly from one another. Furthermore, within a
given genus, the species are far from uniform, many of them differing in
characters usually considered to be of high taxonomic
value. The genus Oxanthera, for example, has only four species, but they run the whole gamut of ovarial morphology: O. aurantium has a hypomerous ovary with two locules; O. fragrans has an isomerous ovary with 5 to 6 locules; whereas O. neo-caledonica has
a hypermerous ovary with seven locules. Several other
genera in the subtribe have aberrant species and doubtless others will
be discovered in the future. No other subtribe in the whole
orange subfamily gives such strong evidence of containing species that
have been for ages and probably still are rapidly evolving into new
forms, new species, and new genera.
The three groups of genera within the subtribe Triphasiinae are indicated in the key to the genera and are described briefly in the text. The Wenzelia
group has four genera, all with more than two ovules (4 to 8, usually
6) in each ovary locule and long, simple or unifoliolate leaves, with
very short nonarticulated petioles except in Oxanthera. The Triphasia
group contains two genera, the species of which are all small trees or
shrubs with short nonarticulate petioles. Two species of Triphasia have simple leaves and one has trifoliolate leaves; the other genus in the group, Pamburus, has simple, semicoriaceous thick leaves. The Luvunga
group has two genera, both woody lianas that clamber over trees by
means of recurved or hooked spines, with small or medium-sized ovate or
subglobose fruits that look like miniature limes.
The remote ancestors of our cultivated
citrus trees doubtless were very like some of the plants now found in
this subtribe. Doubtless several tens of millions of years
have elapsed, however, since the subtribe Citrinae arose from some
ancestral species similar to those now classed in Triphasiinae.
The forty-six species known in
Triphasiinae make it the second largest of the three subtribes in the
tribe Citreae. It contains the nearer wild relatives of our
Citrus Fruit Trees, all of which should be introduced into culture,
studied, tested and utilized as rootstocks or in other ways by citrus
growers and citrus experts the world over. It is noteworthy
that no fewer than twenty-nine species (nearly three fifths the total
number!) have been described as new and also that three of the eight
genera have been established since 1900. As the rich flora
of the Monsoon region is more and more actively assembled by competent
collectors and studied by expert taxonomists, there is good reason to
expect that many more species and doubtless some new genera will be
discovered in the future.
GROUP A. THE WENZELIA GROUP
The Wenzelia group consists of four genera: Wenzelia, Monanthocitrus, Oxanthera, and Merope.
The first three have six ovules in each ovary locule and the last one
has four ovules to each locule. The leaves of the plants of
all four genera are simple or unifoliolate. Wenzelia, Merope, and Monanthocitrus all occur in New Guinea and are closely related genera. Oxanthera, found in New Caledonia, in spite of its long isolation in both time and space, is still obviously related to Wenzelia. Merope has leaves very like those of Wenzelia and Monanthocitrus,
but each ovary locule, so far as known, contains four (or by abortion
two?) ovules and its curious flattened seeds, the largest known in the
orange subfamily, are of unusual shape, being more or less
caudate. Merope is doubtless an early offshoot from an ancestral form of the Wenzelia group. Wenzelia and Monanthocitrus
differ greatly from all the other Minor Citroid Fruit Trees in having
large leaves with extremely short petioles not articulate with the leaf
blade.
In Oxanthera the leaves, the ovaries, and the stamens have varied from the primitive pattern found in Wenzelia and Monanthocitrus. In Merope the seeds have evolved along new lines; in Monanthocitrus the seeds have continued to evolve along lines shown by certain flat-seeded species of Wenzelia until they now show characters found nowhere else in the orange subfamily. Clymenia, a True Citrus Fruit Tree, has leaves very like those of Wenzelia but the fruit shows stalkless pulp-vesicles that pave the way to Citrus.
All the plants of the Wenzelia group should be studied attentively to throw all the light possible on the origin of Citrus.
VI. Wenzelia Merr.
VI. Wenzelia Merr. Phil. Jour. Sci. Bot. 10:272. 1915.
Type species.—Wenzelia brevipes Merr., from Leyte Island, Philippines (Wenzel, No. 998). Herb. Bur. Sci., Manila.
Distribution.—Southern Philippines, New Guinea, Bougainville island, Solomon Islands, Fiji Islands.
Common name.—Wenzelia.
Shrubs with unarmed twigs or with single
or paired spines in the leaf axils; leaves large (7-28 cm long), oblong
or lanceolate; petioles very short (2-5 mm long), wingless but channeled
above, not clearly articulated with the leaf blade; flowers often very
large; solitary in the axils of the leaves, white; calyx 5-lobed; petals
5, oblong-lanceolate or ovate, obtuse or subacute, glandular-punctate;
stamens 10, free, anthers long; ovary oblong-ellipsoid, 4-5-locular with
6 (or sometimes 8) ovules in each locule, narrowed below into an
annular or shallow cupulate disk; fruit obovoid or ellipsoid, 3-5 cm
long, with coriaceous, glandular pericarp, segments containing mucilage
without pulp-vesicles.
The Wenzelia genus is very different from all the other Minor Citroid Fruit Trees of the subtribe Triphasiinae except Monanthocitrus in
having large, or very large, simple leaves, with very short wingless
petioles not articulated with the leaf blade, and in having six or eight
ovules in each locule of the ovary. The fruits are
ellipsoid and the locules contain several seeds (up to six or eight)
immersed in a mucilaginous material in young fruits.
Nine species of Wenzelia are
known, six from New Guinea, one from the southern islands of the
Philippines, one from the Solomons, and one (the easternmost
large-seeded member of the orange subfamily) from Fiji.
Seven of the species fall into two groups constituting the two subgenera
described below, leaving two species still inadequately known and of
uncertain relationships.
Wenzelia is the largest and most
widely distributed of the six genera limited to the southern part of the
Monsoon region, Melanesia, and the Fiji Archipelago, the southeastern
area of distribution of the orange subfamily. Three of these
six genera, Clymenia (Bismarck Archipelago), Monanthocitrus (New Guinea), and Eremocitrus (northeastern Australia), are monotypic; Oxanthera (New Caledonia) has four species; Microcitrus (northeastern Australia and southern New Guinea) has six species; Wenzelia (the Philippines, New Guinea, the Solomons, and Fiji) has nine species!
A striking proof of the recent rapid advance of our knowledge of Citrus relatives is provided by the fact that all the nine species now constituting the genus Wenzelia
have been described since 1900. The first species was
published in 1901, the second in 1910, the third in 1915 (when the genus
Wenzelia was established), a fourth in 1918, and the other five were described early in 1940 (see Swingle, 1940a).
It is very probable that still other species of Wenzelia
will be found when New Guinea, the Spice Islands (the Moluccas), and
the Melanesian islands to the east of New Guinea are explored more
thoroughly. Keys to the subgenera and species of Wenzelia are presented.
Subgenus Wenzelia
Subgenus Euwenzelia Swing. in Webber & Batchelor, Citrus Indus. 1:216. 1943.
This subgenus includes Wenzelia brevipes, W. tenuifolia,and W. kambarae. These species occupy the two extremes of the area of distribution of the genus, as well as a midway location in New Guinea: W. brevipes (the type of the subgenus) is native to the southern islands of the Philippines, W. kambarae to the Lau Group of the Fijis, and W. tenuifolia to southeastern New Guinea.
These species probably resemble the ancestral type of the subgenus Wenzelia, whereas those of the subgenus Papualimo represent a more highly specialized type of later origin.
1. Wenzelia brevipes Merr. Phil. Jour. Sci. Bot. 10:272. 1915.
Type.—Leyte Island, Buena Vista near Jaro, Philippines (Wenzel, No. 998). Herb. Bur. Sci., Manila.
Distribution.—Southeastern Philippines: Leyte, Samar, and Bohol islands and eastern Mindanao Island.
Common name.—Philippine wenzelia.
Merrill’s original extended description
in English, following the Latin diagnosis, reads as follows: "An erect,
glabrous, unarmed shrub about 1 m high, the trunk about 3 cm in
diameter. Branchlets slender, terete, greenish-olivaceous
when dry. Leaves alternate, simple, presenting no indication
of a joint between the lamina and the petiole, firmly chartaceous to
subcoriaceous, oblong, pale when dry, shining, 14 to 25 cm long, 5.5 to
6.5 cm wide, distinctly glandular-punctate, entire, apex acuminate, base
obtuse to rounded; lateral nerves about 10 on each side of the midrib,
prominent on the lower surface, arched-anastomosing, the primary
reticulations lax, prominent; petioles 2 to 4 mm long.
Flowers white, fragrant, axillary, solitary, their pedicels about 1 cm
long with 2 basal, oblong-ovate, 2 mm long bracteoles. Calyx
5 to 6 mm long, cup-shaped or somewhat campanulate, 5-lobed,
glandular-punctate, the lobes very broadly ovate, rounded, about 2 mm
long, wider than long. Petals 5, imbricate, up to 3.4 cm
long and at least 8 mm wide, oblong-oblanceolate, obtuse, narrowed
below, prominently glandular-punctate. Stamens 10, free;
filaments linear, 1.4 cm long, equal, rather slender, cylindric; anthers
oblong, basifixed, 2-celled, about 3.8 mm long. Disk
somewhat cup-shaped, 1.5 mm in diameter, forming a short
gynophore. Ovary oblong-ellipsoid, glandular, about 4 mm
long and 2.5 mm in diameter, 4- or 5-celled, narrowed below into the 2
to 3 mm long stalk, and above into the cylindric style, which is about 9
mm long, continuous with the ovary, ultimately deciduous; stigma
subcapitate, very obscurely lobed; ovules 6 in each cell, 2-seriate,
axile. Fruits obovoid, 3-4 cm long, base narrowed, the
pericarp coriaceous-fleshy, glandular; seeds few, apparently 3 or 4 in
each fruit, the cotyledons thick, fleshy, oblong-obovoid, about 1.5 cm
long and 1 cm wide."
Some of the later collections show
broader leaves than those of the type specimen described by
Merrill. For example, a specimen from Bohol, collected by M.
Ramos (No. 43189), has leaves 13.0 to 17.5 by 6.5 to 8.5 cm, acuminate
at the tip, broadly rounded or even slightly cordate at the base,
petioles very short, 4 to 5 mm long, 2 to 2.5 mm in diameter, more or
less longitudinally rugose, not articulated with the leaf blades; flower
buds single, axillary, 15 by 4 to 5 mm, pedicel 1 cm long, slender (0.6
to 0.8 mm diam. at base, 1 to 1.3 mm diam. at tip).
1a. Wenzelia brevipes var. alabatensis Swing. Jour. Arnold Arbor. 21:16. 1940.
Type.—Philippines, Alabat Island (Ramos and Edaño, No. 48054, Bur. Sci.). Herb. Arnold Arbor., Harv. Univ., Cambridge.
Distribution.—Known only from type locality.
Leaves narrow (22-28.5 X 5-6.6 cm), much
narrower than those of the species; oil glands less conspicuous,
especially on lower surface.
This variety occupies the northernmost point of the range of the species W. brevipes. Like the species itself and like all other species of the genus Wenzelia,
it is native in an island on the western boundary of the Pacific
Ocean. There is some variation in the shape of the leaves in
the species of the genus Wenzelia, but no other species shows so
extreme a variation as that represented by this variety with its
extremely long and narrow leaves, also peculiar in their less
conspicuous oil glands. It may prove to be an extreme form
connected with the typical form of the species by intergradations.
2. Wenzelia tenuifolia Swing. Jour. Arnold Arbor. 21:14. 1940.
Type.—Southeastern New Guinea,
Papua, Boridi, forests, alt. about 1,220 (or 3,353) meters, "c[irca]
4,000 [or 11,000] feet" (C. E. Carr, No. 14881, 2 branches, 1 fruit,
February 1, 1935). Herb. Bot. Mus., Berlin-Dahlem;
photographs and serial microtome sections, Herb. Natl. Arbor.,
Washington, D.C.
Distribution.—Known only from the type locality.
A spineless shrub, 2 m high; ultimate
branches slender, 1.1-1.8 mm in diam., internodes 2-3 (rarely 5) cm
long; leaves very thin, brittle when dry, more or less broadly
elliptical 10-13 cm long including petiole, 5-7.2 cm wide, apex bluntly
rounded and often imperfectly developed, the very tip being stunted and
more or less torn, sometimes more or less irregularly emarginate,
broadly cuneate at the base, margins entire, lateral veins, 10-12 pairs,
arising at angles of 65°-80° with the midrib, petioles 4-6 X 1-1.1 mm;
fruit ovate, 3.5 cm long, 3 cm broad, 5-loculate, radial locule walls
thin, 1-1.5 mm thick but expanding into a thick rib of tissue running
longitudinally in the fruit, more or less triangular in cross section,
4-7 mm in radial thickness, dorsal locule walls only 1-2 mm thick midway
between the radial walls; seeds dull brown, ovate, compressed, 17-19 X
12-15 X 3.5-5 mm, more or less wedge-shaped, with a faintly, more or
less concentrically marked and corrugated edge, 1-2.2 mm wide and 1-1.5
mm thick, on one side of the seed, with faint markings 0.2-0.4 mm apart,
1-4 in a locule, often occurring in closely approximated pairs; embryo
monoembryonic.
This species was known to Swingle only
from the rather scanty type specimen, but it is so evidently distinct
from all the other known species that he had no hesitation in making it a
new species. It is somewhat of a connecting link between
the two subgenera Wenzelia and Papualimo but apparently falls in Wenzelia,
as the seeds lack the paper-thin, more or less torn membrane along the
free margins of the seeds found in the species of the subgenus Papualimo.
The fruits of W. tenuifolia are
circular in cross section and show five more or less triangular
peripheral ribs at the distal ends of the radial locule walls, which
fill the spaces between the strongly bulging dorsal locule
walls. In striking contrast to this species, W. archboldiana has
fruits which are bluntly star-shaped in cross section because of the
absence of any tissues filling the interlocular furrows.
The collector’s label on the type
specimen is a carbon copy (the original label was doubtless used for
another specimen of the plant). The altitude given on the
label apparently reads "c. 11,000 feet" but may possibly be "c. 4,000
feet." If the altitude is 4,000 feet (1,220 meters), it
would be far above the usual upper limit for the aurantioid plants in
New Guinea (about 300 meters, or 984 feet). If the altitude
is 11,000 feet (3,353 meters), it would equal the highest altitude as
yet reported for any rutaceous plant from New Guinea.3
As all the other species of Wenzelia grow at low altitudes in tropical regions, it will be of interest to learn more about the distribution of W. tenuifolia.
Perhaps its curious unusually thin leaves may be adapted for growth in
very humid locations, such as occur in the cloud belts of mountains.
3. Wenzelia kambarae Swing. Jour. Arnold Arbor. 21:12. 1940. Atalantia sp. Albert C. Smith, Fijian Plant Studies Bul. 141:77. 1936. Illus. Swing., loc. cit. pl. 3, figs. 6-8.
Type.—Fiji Archipelago, Lau Group,
Kambara Island, limestone formation, alt. 10-100 m (A. C. Smith, No.
1265). Herb. New York Bot. Gard.
Distribution.—Fiji Archipelago:
Lau Group, Kambara Island (A. C. Smith, Nos. 1265 and 1293), and Naiau
Island (Zimmerman). Herb. Natl. Arbor., Washington, D.C.
Common name.—Fiji wenzelia (or moli moli).
A spineless shrub or slender, small tree,
4-7 m high, trunk 4-8 cm diam., twig slender, 1-3 mm diam., glabrous,
at first green but soon turning light brown and showing numerous
irregular, more or less anastomosing, longitudinal, very narrow ridges;
leaves thin, chartaceous, oblong to elongate-elliptical, varying
considerably in size and shape, 6-21 X 3-8.5 cm, bluntly pointed or
rounded at apex, broadly cuneate or rounded at base, margins entire or
irregularly and shallowly crenate (Zimmerman's Naiau material), lateral
veins very distinct on under surface, less distinct above, 8-13 on each
side arising at rather widely varying angles (60°-80°) with the midrib,
branching dichotomously at 3/5-4/5 of the distance to the margin,
petioles 5-7 X 1.5-2 mm, tapering into the leaf blade with a very
shallow channel on the upper side formed by the decurrent leaf margins,
petioles on old leaves often brownish and irregularly ridged or rugose,
as is the midrib on the lower surface; flower buds (coll. by Zimmerman,
Naiau Island, very young) 2.5 X 2 mm, borne on slender pedicels 8-9 mm
long, bearing several minute pointed bracts on the lower portion; fruits
orange colored, 3-4 cm diam., 3- (or 4-?) locular with a gland-dotted
but smooth peel, borne on pedicels 14-16 X 1.8 mm, with a cylindrical
carpophore 1.2-2.5 mm long between the persistent calyx and the base of
the fruit; seeds very large, ovoid, 18-25 X 12-15 mm, testa smooth,
shiny, cream-colored, embryos 1 or 2 (sometimes more?),
greenish-colored.
This species is the easternmost large-seeded Citrus
relative that occurs on any Pacific island. Its seeds are
so large that it is improbable that they would have been carried to Fiji
by birds, especially since the fruits contain no pulp and little if any
mucilaginous matter. It is highly probable that the moli moli reached the Fiji Archipelago from the center of origin of the genus Wenzelia
(probably New Guinea) by slowly spreading eastward over dry land, a
migration that probably required millions of years to
accomplish. Its nearest known relative is W. melanesica,
native to Bougainville Island in the Solomons, about 1,800 kilometers
to the west-northwest. That dry land once extended from the
west as far east as Fiji in the early Tertiary epoch is considered
certain by some geologists ((Brock, 1924, p. 75).
Dr. Edward C. Zimmerman, who obtained
flower buds of this plant by "shooting" the dangerous surf on the atoll
surrounding Naiau Island, thus making identification possible, wrote
Swingle that the natives of the Lau Group know the plant well by the
name moli moli; furthermore, they told him that there were pink and red flowers, perhaps in different stages of development (all other Wenzelia
flowers so far observed are white). The trees on Naiau
Island were taller (5 to 7 m) than those reported from Kambara Island (3
m), but the leaves of the Naiau plants were much smaller (6 to 10 by
2.5 to 5 cm) than those of one of the collections (A. C. Smith, No.
1265) from Kambara (11.5 to 21 by 4 to 8.5 cm). However,
another collection from Kambara Island (A. C. Smith, No. 1293) shows
smaller leaves (8 to 12 by 2.5 to 5 cm). Probably W. kambarae is a variable species showing many forms.
Subgenus Papualimo
The subgenus Papualimo includes four species, W. platysperma (the type of the subgenus) W. paludosa, W. melanesica, and W. archboldiana, all native to New Guinea or the Solomon Islands to the eastward.
Wenzelia paludosa (Lauterb.) Tan., which has very thin seeds (only 1 to 2 mm thick), almost certainly falls in the subgenus Papualimo, although nothing is known about the margination of the seeds, a striking character of the other species of this subgenus.
The species constituting the subgenus Papualimo
represents a striking new evolutionary tendency as shown in the
development of thin seeds with very thin, laciniate membranous
margins—seeds that differ widely from the ancestral type of the genus Wenzelia
and from all the other genera of the orange subfamily. This
evolutionary tendency has apparently reached its highest development in
the very strange monotypic genus Monanthocitrus, also native to
New Guinea, which has still thinner, still more elaborately margined
seeds. The seeds are also spotted, unlike those of any other
species known in the orange subfamily.
4. Wenzelia platysperma Swing. Jour. Arnold Arbor. 21:11. 1940. Illus. Swing. loc. cit. pl. 3, figs. 4, 5.
Type.—New Guinea, Papua, Palmer
River, 2 miles below junction of Black River, alt. 100 m, flood-plain
forest undergrowth (L. J. Brass, No. 7111, branch with fruit), Herb.
Arnold Arbor., Harv. Univ., Cambridge; also found in the ridge forest
undergrowth at the same locality (Brass, No. 7025, branch with fruit),
Herb. Arnold Arbor.
Distribution.—Known only from the two above-cited collections, made very close together.
A thornless, loosely branched, small
tree, 3 m high; twigs slender, 1-2 mm diam., internodes 2-3 cm long,
often bent slightly at each node alternately to the right and left,
glabrous or very minutely and sparingly pubescent; leaves chartaceous,
elongate-elliptical, 10-20 X 2.5-5.5 cm, acuminate or caudate at apex,
cuneate, or broadly rounded at base, margins irregularly crenulate (and
also denticulate in Brass No. 7025), lateral veins 12-14 on each side,
arising at angles of 70°-80° with the midrib, branching dichotomously at
1/4-3/4 of the distance to the margin, petioles very short, 3-4 X
1.4-1.8 mm (1/40-1/60 of the length of the leaf blade), with a shallow
channel on the upper side; flowers not seen, calyx persistent,
subtending the fruit, deeply lobed, lobes 2 X 2 mm, broadly rounded,
minutely puberulent (glabrous and apparently slightly fleshy in Brass
No. 7025); fruits subglobose or ovate, 4-4.8 X 3.5 cm, 4-locular (?),
reddish or pink, borne singly on a slender pedicel 10-12 mm long,
arising in the axil of the uppermost leaf; seeds flattened, light brown,
12-15 X 7-9 X 2-3 mm, testa rugose on edges or else tapering into
irregularly shaped extensions with somewhat torn margins, monoembryonic,
cotyledons greenish.
This remarkable species is known only
from two single fruiting twigs. Both collections show zigzag
slender twigs each with a single fruit borne in the axil of the
uppermost leaf. The seeds are even flatter than those of W. archboldiana,
but otherwise they are much the same. The globose or ovate,
pink or reddish, gland-dotted, aromatic fruits hang down at the ends of
the fruiting branches. There is no trace of pulp or
mucilage between the crowded seeds that lie lengthwise in the carpels.
5. Wenzelia paludosa (Lauterb.) Tan. Jour. Arnold Arbor. 9:139 1928. Citrus paludosa Lauterb. Bot. Jahrb. 55:263. 1918.
Type.—Northeastern New Guinea, in
swampy primeval forest with sago palms and rattan at mouth of Sepik
River (Ledermann, Nos. 7173 [flowers] and 7507a [fruits]). Herb. Bot. Mus., Berlin-Dahlem.
Distribution.—Northeastern New Guinea: known only from the Sepik River.
The original description of Lauterbach,
translated, reads as follows: "Shrub or small tree, with smooth,
slender, terete branches, and stout solitary spines; petioles short,
caniculate above; leaves lanceolate, gradually narrowly acuminate,
acumen obtuse, emarginate [at the tip], slightly rounded or subacute at
base, chartaceous, glabrous on both sides, opaque, dull green when dry,
12-14 lateral veins, oblique, dividing near the margin, many [of them]
arched-anastomosing, prominent above when dry like the midrib, margins
undulate-crenate, minutely subdenticulate; flowers axillary, solitary;
calyx 5-lobed, lobes ovate, rounded, ciliate; petals 5, ovate, subacute,
glandular on outer side; stamens 10, filaments free, anthers linear;
disk annular; ovary flask-shaped, locules many-seeded; style thick,
stigma 5-lobed; fruit ovate, subacuminate, exocarp moderately thick,
glandular, pulp scarcity visible; seeds up to 6 in each locule,
irregularly triangular or quadrangular, much flattened, testa white,
coriaceous, slightly rugose.
"Shrub, 1-2 m high, or small tree, with
light gray bark. Branches 2-3 mm thick; petioles 2-5 mm;
leaves 7-14 cm long, 2-5 cm wide; spines 10-12 mm; flower pedicel 6
mm. There are only 2 not fully developed [flower] buds that
measure 3 mm. Fruit pedicel 10 mm; the ripe fruit, which
smells like an orange, is 4 cm long by 3 cm diam.; the seeds 10-12 mm
long, 1-2 mm thick."
A later collection (Ledermann, No. 12252)
was made at a hill camp on the Sepik River. The type
specimen showing fruits (Ledermann, No. 7507a) has pedicels of the young fruits 10 to 12 mm long and unusually slender for a species of Wenzelia,
being only about 0.5 mm in diameter in the middle, tapering to about 1
mm at the base and also at the top where it bears the calyx without any
gradual expansion into the funnel-shaped base of the calyx as in W. melanesica.
The young fruit is ellipsoid, 14 by 5 mm, narrowed into a slender stalk
at the base, 3 mm long by 1.5 mm thick, and attenuate at the apex into a
beak about 2 mm long and 1 mm wide. The seeds are
flattened, as are those of W. platysperma and W. archboldiana from the eastern half of New Guinea and W. melanesica
from the Solomons, but unfortunately it is not known whether they are
margined or not, and if so with what kind of a margin. The
petioles are very short, 3 to 4 mm long and 1.5 mm wide, with a shallow
channel on the upper side that is broad at the tip and narrows regularly
toward the base. The lateral veins arise at a highly
variable angle (40° to 65°) with the midrib, and branch dichotomously at
from slightly less than one half to nearly three fourths of the
distance from the midrib to the margins of the leaf.
This species seems to be clearly distinct from all the others in the genus.
6. Wenzelia melanesica Swing. Jour. Arnold. Arbor. 21:9. 1940. Illus. Swing. loc. cit. pl. 2, figs. 6-8; pl. 3, figs. 1-3.
Type.—Solomon Islands, Bougainville Island, Kugu-maru, Buin (Kajewski, No. 1907a). Herb. Arnold Arbor., Harv. Univ., Cambridge.
Distribution.—Known only from the type locality.
Small thornless tree (up to 7 m); twigs
glabrous, slender, 1-2.5 mm diam.; leaves thin, chartaceous, glabrous,
elliptical, with very numerous minute oil glands evenly distributed over
the whole surface, acuminate at the apex, which ends in a sharp point,
broadly and evenly rounded at base, 10-16 X 3.5-5.5 cm, margins entire
or slightly crenulate; lateral veins clearly marked below, 12-15 pairs,
arising at a large angle (70°-80°) with the midrib; petioles very short,
4-5 X 1-1.3 mm, glabrous, not articulated with the blade, with a
narrow, very shallow channel on the upper side, the walls of which
connect with the leaf margins; flowers solitary or in small groups (2-3)
in the axils of the leaves, pedicels with a few sparse, short hairs,
short (4-6 mm), with very small ciliate bracts at the base, slender,
expanding gradually into the funnel-shaped calyx; calyx 4-5 lobed, lobes
broadly rounded or very bluntly pointed, 1.3-2 mm long, 1.5-2 mm wide,
and increasingly short-pubescent toward the margins, which are
abundantly short ciliate; corolla with 4-5 petals (immature in type
specimen), showing (in the bud) numerous oil glands evenly distributed;
stamens 8-10; pistil immature, ovary with 4-5 locules, each with 6
ovules; fruits 4-5 angled, tapering to a sharp point at the apex, 4.5 cm
long, 2.3 cm wide, peel showing numerous, evenly distributed small
(0.1-0.2 mm), slightly sunken oil glands; seeds thin, flat or nearly so,
ovate in outline, 9-13 X 6.5-9 X1.5-2 mm, dusky gray, very thin at the
edges, with a lighter colored, narrow, usually subentire, marginal
membrane; embryo monoembryonic.
This striking species of Wenzelia extends the range of the subgenus Papualimo from New Guinea to the Solomon Islands (Long. 156° E.). It resembles most closely W. archboldiana from New Guinea but differs from it in having 4- to 5-angled fruits tapering into a sharp point.
7. Wenzelia archboldiana Swing. Jour. Arnold Arbor. 21:7. 1940. Illus. Swing. loc. cit. pl. 2, figs. 1-5.
Type.—British New Guinea, lower
Fly River opposite Sturt Island in rain-forest (L. J. Brass, No. 8038,
fruiting branches). Herb. Arnold Arbor., Harv. Univ.,
Cambridge.
Distribution.—Southeastern and
eastern New Guinea. In addition to the type, two other
collections from northeastern New Guinea were seen: Morobe district,
Ulap, 610 m alt. (Clemens, No. 6613, flowering branches), Herb. Natl.
Arbor., Washington, D.C.; and Morobe district, above Sattelberg (J. and
M. S. Clemens, No. 1057, branches with young fruit), Herb. Bot. Mus.,
Berlin-Dahlem.
Common name.—Archbold’s wenzelia.
A thornless shrub or small tree, 3-5 m
high; twigs glabrous, 2-4 mm diam.; leaves ovate-lanceolate or
lanceolate, 16-22 X 7-9 cm, more or less abruptly acuminate at apex,
cuneate at base, margins entire or slightly crenulate, lateral veins
10-14 on each side, arising at angles of 60°-70° with the midrib,
usually branching dichtomously [sic] at 1/2-3/5 of the distance
to the margin, petioles very short, 4-8 X 1.5-2 mm (1/25-1/40 of the
length of the leaf blade), with a shallow channel on the upper side;
flowers usually arising in pairs in the axil of the terminal leaf,
flower buds 2.3 X 3-4 mm, pedicels 4-5 X 0.8-1 mm, expanding gradually
into the funnel-shaped calyx 4-5 mm long and 3-4 mm wide at the top,
calyx lobes short (1 mm long, 3 mm wide), broadly rounded, minutely
pubescent on the back and margin; corolla white, petals 4 (or 5),
measuring 15 X 4.5 mm in the bud, dotted with small oil glands,
glabrous, margins thin and slightly scarious; pistil 12-12.5 mm long
immediately after the petals fall, disk short, 0.9-1 mm high, 1.7 mm
wide, abruptly constricted to 0.9-1 mm wide at junction with ovary base;
ovary clavate with a sterile narrowed base, 6-7 X 1.7-3 mm, 5- (or 4-)
locular, with 6 or 8 ovules in each locule, style cylindrical, 4.5-5 X
0.5-0.6 mm, not expanded at junction with ovary tip and only slightly
expanded at stigma junction, stigma cushion-shaped, 1 mm high, 2 mm
wide; fruits commonly paired in axil of uppermost leaf of fruiting twig,
"lime green and smelling of limes," depressed-globose, 2.5-3 X 3-3.5
cm, 5-locular (in type), each locule bulged out (radial diam. 14-15 mm
at junction with adjoining locule and 17-18 mm midway between the two
radial locule walls) making fruit star-shaped in cross section with very
blunt, rounded rays; seeds several (up to 6 or 8), crowded into each
locule, flat and more or less curved, arranged more or less radially
with their long diameters parallel to the axis, 15-17 X 10-11 X 1.5-3.5
mm, brownish-gray (after soaking in formaldehyde solution),
monoembryonic.
The flowers of this species were
described from Clemens No. 6613, as the type specimen showed fruits
only. The most extraordinary character of the species—its
numerous flattened seeds—is one which it shares with three other
species, W. platysperma, W. paludosa, and W. melanesica. This
flattening of the seeds is undoubtedly not merely a result of the
competition for space by the numerous seeds that develop in each locule,
but is an inherited adaptation. These flat-seeded species
of Wenzelia are obviously related to Monanthocitrus cornuta, but it must be emphasized that in Monanthocitrus the
seeds are not merely very much flattened, but are so compressed and
crowded that they are distinctly saucer-shaped, concave on one side and
convex on the other, with a thin, more or less fimbriate membrane almost
entirely surrounding all but the attached side.
Furthermore, the seeds of Monanthocitrus are conspicuously spotted, a character not found, so far as known, in any other plant belonging to the orange subfamily.
The mature fruits of the type specimen of W. archboldiana show
a curious abnormality, having fusiform cracks in the outer layer of the
peel arising usually near the middle of the dorsal wall of the locules
just above the attachment to the pedicel. The split in the
peel reveals the more or less dried-up oil glands and other tissues, but
the inner peel apparently remains intact. Sometimes these
fusiform cracks occur between the locules of the fruit, although usually
not so abundantly.
The depressed-globose, ribbed, green
fruits (said to smelt like limes) usually appear in pairs in the axil of
the uppermost leaf on the fruiting twig—in striking contrast to W. platysperma,
where the more or less elongated subglobose or ovate pink fruits are
borne singly, and hang down apparently at the tip of the twig, although
in reality in the axil of the uppermost leaf.
This species has been named in honor of
Mr. Richard Archbold, who organized and led three great collecting and
exploring expeditions to New Guinea. He employed expert
collectors, among them L. J. Brass, with the result that many herbarium
specimens of the remarkably interesting plants of New Guinea were
brought back.
SPECIES INADEQUATELY KNOWN AND OF UNCERTAIN RELATIONSHIPS
8. Wenzelia dolichophylla (Lauterb. & K. Schum.) Tan. Jour. Arnold Arbor. 9:139. 1928. Citrus dolichophylla Lauterb. & K. Schum. in Schum. & Lauterb. Fl. Deut. Schutzgeb. 377. 1901.
Type.—Northeastern New Guinea,
tributary river No. 9, of Ramu River (Lat. 4° 20' S., Long. 144° 38'
E.), high forest, altitude 60 m (Lauterbach, No. 3108).
Herb. Bot. Mus., Berlin-Dahlem.
Distribution.—Known also from the
upper course of the Gogol River, northeastern New Guinea, and a sterile
specimen (doubtfully this species) reported by Lauterbach from Etna Bay
(Lat. 4° S., Long. 134° 30’ E.) in northwestern Dutch New Guinea (now
West Irian, Indonesia).
The original description, translated,
reads as follows: "Shrub with numerous slender young fruiting branches,
glabrous, terete; petioles very short, furrowed above; leaves
ovate-lanceolate or ovate-oblong, very acutely attenuate-acuminate,
glabrous on both sides, coriaceous; immature fruits long-pedicellate,
subglobose, somewhat acute, glabrous. A shrub 2 m
high. The branches are 20-25 cm long and 2-3 mm thick at the
base; they have gray to brown bark. The petiole is 3-5 mm
long, no articulation of the leaf blade with the petiole is visible;
leaves 15-25 cm long and at the middle or lower third 5.5-8.5 cm broad,
with 14-18 pairs of veins arising at right angles from the mid-rib, less
prominent above than below; gray above, yellowish below, dull on both
sides. The pedicel is 2-2.5 cm long. The
immature fruits, still green, have a lemon-like odor."
Lauterbach reported (1918, p. 262) on a
specimen from the upper course of the Gogol River (Lauterbach, No. 1088)
collected in fruit, November 26, 1890, as follows: "The nearly ripe
fruits are red, lemon-shaped, 5.5 cm long and 3.5 in
diameter." These are the largest fruits yet reported in this
genus and the red color is also distinctive. Swingle
examined the type specimen in the herbarium at Berlin-Dahlem many years
ago and found no trace of pulp-vesicles, the locules of the dry fruits
being filled with a brown, brittle, resin-like substance.
9. Wenzelia grandiflora (Lauterb.) Swing. Jour. Wash. Acad. Sci. 28:532. 1938. Citrus grandiflora Lauterb. Nova Guinea 8:293. 1910; Monanthocitrus grandiflora (Lauterb.) Tan. Jour. Arnold Arbor. 9:139. 1928.
Type.—Central-western New Guinea
[West Irian, Indonesia], swampy primeval forest, Bivak Island, in Noord
Fluss [Lorentz River] (Lat. 5° 0' 25" S., Long. 138° 39' E.), (Versteeg,
No. 1788). Herb., Utrecht.
Distribution.—Known only from the type locality.
The original description of Citrus grandiflora
by Lauterbach reads, translated, as follows: "Shrub 1-2 m; branches
slender, spiny, 2-4 mm thick, terete, flattened when young; spines 2,
about 1 cm long, borne in the axils of the leaves; leaves lanceolate,
alternate, acuminate [at the tip], acumen acute, broadly pointed at
base, 15-20 cm long, 5-7.5 cm wide, coriaceous, margin
crenulate-subdentate, veins more prominent below, 12-13 pairs,
ascending, anastomosing; petioles 5 mm long, subterete; flowers solitary
(?), axillary (?), with short pedicels; calyx cupulate, 4 mm long,
5-merous, lobes triangular, subacute or somewhat truncate, 2 mm long;
petals 5, white, lanceolate, broadly pointed ('late acutis') [at the
tip], attenuate at base, 35 mm long, 11 mm wide; stamens 8, free,
filaments 11 mm long, enlarged at the middle, anthers oblong, 3.5 mm
long; disk 1.5 mm long, somewhat pentagonal; ovary substipitate, ovate, 3
mm thick, 5-locular, locules with many ovules; style 1 mm thick, 6 mm
long, stigma dilated, truncate, pentagonal."
Unfortunately, the fruits of this species
are unknown, but in its flower, leaf, and petiole characters it agrees
very well with Wenzelia. It is the only species of Wenzelia
that has paired spines. However, the number of spines is
variable in the genus, six species having no spines and two, W. paludosa and W. dolichophylla, having solitary spines, although the latter species is sometimes spineless.
Wenzelia grandiflora was first described as a species of Citrus. Many years later it was transferred to the monotypic genus Monanthocitrus because the two showed agreement in having paired spines in the axils of the leaves. However, the flowers of Monanthocitrus are very much smaller than those of any species of Wenzelia, the petals being only one seventh as long as those of W. grandiflora! Until fruits with mature seeds are found this latter species must stay in the genus Wenzelia.
VII. Monanthocitrus Tan.
VII. Monanthocitrus Tan. Jour. Arnold Arbor. 9:138. 1928. Illus. fig. 3-11.
Type species.—Citrus cornuta Lauterb. = Monanthocitrus cornuta (Lauterb.) Tan.
Distribution.—Southwestern Dutch
New Guinea [West Irian, Indonesia]: near Alkmaar (Lat. 4° 40' S., Long.
138° 44' E.) on the Lorentz River and Signal Hill, a few miles west of
Alkmaar (see van Nouhuys, 1923, pl. 4).
Common name.—Spotseed-lime (or monanthocitrus).
Twigs slender, slightly angled when
young, soon cylindrical, internodes long (2-4 times as long as the
petioles); spines paired or single (rarely 3, or wanting), very slender,
about half again longer than the petioles; leaves simple, 14-22 cm
long, elliptical, caudate-acuminate at the tips, broadly cuneate at the
base, glabrous, margins entire or slightly wavy; lateral veins 10-15
pairs, visible on both sides; petioles very short (shorter than the
spines and less than 1/20 as long as the leaf blade), wingless,
flattened on the upper side, not articulated with the leaf blade; flower
buds ovoid or ellipsoid, borne on slender pedicels as long or longer
than the petioles; flowers small; calyx cupulate, 5-lobed, lobes acute,
short; petals 5, shorter than the petioles; ovary globose, very small,
with 5 locules, each locule with 6 (or sometimes 8?) ovules; style
thick, twice as long as the ovary, stigma 5-lobulate; fruits globose or
slightly ovoid, with thin peel showing numerous slightly depressed oil
glands; locules 5, lined with smooth, cartilaginous walls, without
pulp-vesicles, but containing 6 (or sometimes 8?) seeds surrounded by
mucilaginous fluid; seeds packed tightly in the locule, much flattened,
often concave (like a shallow saucer), testa with many small irregular
dark red-brown spots; a very thin irregularly lobed membrane borders the
seeds except on the attached side.
Monanthocitrus has leaves very much like those of Wenzelia dolichophylla and several other species of that genus. Monanthocitrus is most closely related to the species of Wenzelia belonging to the subgenus Papualimo,
which have flattened seeds bearing on the unattached sides very thin,
more or less torn membranous margins. However, no species of
Wenzelia has the much-spotted seeds (unique in the orange subfamily) found in Monanthocitrus, which also has flowers very much smaller than those of any species of Wenzelia—with petals only one-fifth to one-seventh as long! Doubtless Monanthocitrus arose from an ancestral form much like that of some of the species of Wenzelia of the subgenus Papualimo,
but it has traveled so far on the evolutionary highway that it
apparently constitutes a good genus today. The leaves are
also much like those of Clymenia polyandra (a True Citrus Fruit
Tree of the subtribe Citrinae), which has petioles of about the same
length in relation to the leaf blade as those in Monanthocitrus, i.e., about one-twentieth as long.
Thanks to the kindness of Dr. H. J. Lam,
director of the Rijks Herbarium at Leiden, Holland, Swingle was able to
study the type specimen on which Citrus cornuta Lauterb. was based, upon which species Tanaka based his genus Monanthocitrus. This
type specimen was collected by Versteeg (No. 1551) at Alkmaar in New
Guinea in August, 1907. It carries the fruit described by
Lauterbach, showing curious slender, needle-like outgrowths from the tip
of each carpel. The fruit was still intact and when opened
it showed no trace of pulp-vesicles.
Monanthocitrus cornuta (Lauterb.) Tan. Jour. Arnold Arbor. 9:138. 1928. Citrus cornuta Lauterb. Nova Guinea 8:292. 1910. Illus. fig. 3-11.
Type.—Southwestern Dutch New
Guinea [West Irian, Indonesia], near Alkmaar (Lat. 4° 40' S., Long. 138°
44' E.) on the Lorentz River (Versteeg, No. 1551), Rijks Herb., Leiden.
Distribution.—Known only from the type locality and from Signal Hill, a few miles west of Alkmaar.
Lauterbach's description of Citrus cornuta
(with slight changes in the order of arrangement) reads, translated, as
follows: "Shrub about 1 m high; branches slender, flower-bearing ones
2-4 mm thick, terete, spiny; spines 2 or 3, about 1 cm long, in the
axils of the leaves; leaves ovate-oblong or lanceolate,
attenuate-acuminate, acumen up to 2 cm long, obtuse, sometimes
emarginate, coriaceous, cuneate at base, entire or wavy margined, veins
more prominent below, lateral veins in 10-12 pairs, ascending, thickly
anastomosing by arches near the margin; petioles semiterete, scarcely
channeled above, 5-6 mm long; flowers solitary, axillary, pedicellate;
pedicels 5-8 mm long, subtended by 2-3 acute bracts, 1 mm long; calyx
cupulate, 5-merous, lobes acute, 1 mm long, slightly ciliate under the
lens; petals 5, ovate, subacute, about 5 mm long, whitish flesh-colored
('albis carnosulis'); stamens 10, free, filaments 1.5 mm long, anthers
oblong, 2 mm long; disk annular; ovary globose, 1 mm diam., 5-locular, 2
ovules [? see below] in each locule; style thick, 2 mm long, stigma
5-lobed; fruit globose, rose-colored, 2.5 cm diam. when dry, fleshy, the
apex with 5 solitary mammillae, each crowned by a single spine [-like
appendage] up to 2 cm long.…
"The long spines that form what may be
called horns are very peculiar; as far as can be determined from dry
material they arise from wart-like protuberances at the apex of the
fruit and, in the dry state, fall off easily; 3 are intact; only the
points of attachment of the other two are seen. No trace of
their origin can be seen on the ovaries."
Swingle examined the type specimen of
this species (Versteeg, No. 1551, collected at Alkmaar, New Guinea,
August 2, 1907), lent to him by Dr. H. J. Lam, director of the Rijks
Herbarium at Leiden. It consists of a branch about 20 to 25
cm long, with six leaves (see fig. 3-11).
It bears one fruit, 25 by 32 mm, with well-marked oil
glands. When described by Lauterbach in 1910 the specimen
still had three needle-like appendages arising from the top of the fruit
and the bases of two more. Doubtless there were originally
five of them, one arising from each locule of the fruit.
These needle-like appendages are 20 to 22 mm long and very slender,
about 0.6 to 0.75 mm in diameter at the base and 0.3 to 0.4 mm at the
tip (measured when dry); they have about 20 to 22 shallow furrows, with
narrow ridges between, extending lengthwise. They arise at
the apex of the fruit from wrinkled, glabrous elevations (broadly
conical) of the peel about 2.5 to 3.5 mm wide and 2 to 2.5 mm high; one
of these bases is found on each segment. These remarkable
needle-like outgrowths of the locules of the fruit look like slender
projections of the peel and have the same color as the peel, but do not
show oil glands. The largest leaf blade measures 20.5 by 7
cm; two smaller leaves are 16 by 5.5 cm and 15 by 5 cm. The
petioles are channeled on the upper side, 7 to 8 by 1.5 to 1.6 mm, and
not articulated with the leaf blade; the paired spines are straight, 3
to 12 by 0.5 to 0.8 mm. The single fruit is oval, 30 mm long
and 25 mm wide when dry; when swelled by soaking in hot water it
measured 32 mm long and 28 to 30 mm wide. The greatest
length from the base to the tip of one of the five conical bases on
which the needle-like outgrowths arise is 34 mm. The dried
fruit is buff to cinnamon in color (see Ridgway, 1912, pl.
39). The pedicel is 10 mm long with two very small bracts
attached 2 mm above the base. The calyx lobes are reflexed
when dry, but on soaking they extended out nearly at right angles to the
pedicel, making the salverform calyx 6 to 7 mm wide and about 2.5 mm
high. The calyx lobes are about 3 mm long, thick and bluntly
rounded at the tips, and become very thin at the extreme tips and
sparingly ciliate. When the fruit was cut open, the peel was
seen to be thin, only 1 to 1.5 mm including the locule
wall. The outer peel is 0.6 to 0.8 mm thick; the locule
walls are stiff, cartilaginous, and smooth inside. The
seeds, six (or sometimes eight) in each locule, are crowded into a
bundle nearly filling the locule, which also contains mucilaginous gum, but no pulp-vesicles!
The seeds are very thin, often curved (like a shallow saucer), and have
thin fimbriate margins, cream, buff, or ivory-yellow in color on all
but the attached side of the seed. Including this membrane,
the seeds measure 10 to 11 by 7 to 8 by 1.5 to 2 mm. The
seed proper measures about 8 to 9.5 by 7 to 8.5 mm and is covered with
an ivory-yellow testa which becomes fawn to army brown (Ridgway, 1912,
pl. 40) when wet. This testa shows many (10 to 20 or more)
angular, dark red-brown spots, varying greatly in size from 0.5 to 2.5
mm, usually narrow if long. On well-soaked seeds these spots
varied from dark vinaceous to Indian red (Ridgway, 1912, pl.
27). The inside layer of the testa in contact with the
cotyledons of the embryo shows numerous very small, curved, vermicular
markings of vinaceous brown (Ridgway, 1912, pl. 39). The
seeds contain a single very thin embryo, oval in outline, 8 to 9 by 7 to
8 mm, and 1 to 1.5 mm thick, vinaceous fawn to fawn color (Ridgway,
1912, pl. 40). No oil glands can be detected in the
cotyledons by superficial examination. The very small
radicle projects out 0.5 to 0.8 mm at the base of the
cotyledons. The attached edge of a well-soaked seed showed a
more or less rugose ariloid tissue, 6 to 7 mm long and about 2 mm wide,
which projects 1.5 to 2 mm beyond the seed.
A paratype specimen of M. cornuta
(Versteeg, No. 1551), also collected at Alkmaar, New Guinea, on August
2, 1907, preserved in the herbarium of the Botanical Museum at
Berlin-Dahlem, was photographed by Tanaka, who kindly sent Swingle a
print. It is a single twig with one flower bud, 4.5 by 3 mm,
on a slender pedicel about 7 mm long. One leaf measures 2l
by 7 cm; another, lacking the acuminate tip, measures 18.5 by 8.2 cm,
with a petiole 8 by 1.5 mm. The spines are all paired,
straight, very slender, 8 to 14 mm long and 0.6 to 0.8 mm at the base
and tapering to a very acute point. The lateral veins arise
at a large angle with the midrib, about 65° to 75°, in the middle part
of the leaf blade.
The remarkable needle-like protuberances
that arise at the tips of each carpel of the fruit of the type specimen
are still imperfectly known.4
In a supplementary note on this plant Lauterbach stated (1912, p. 825)
that a specimen collected by von Roemer (No. 633) at Signal Hill, a few
miles west of the type locality at Alkmaar, "had fruits with no trace of
the peculiar spines. Very likely it was a question, in case
of the original specimen of Versteeg, No. 1551, of a mere malformation
that was nevertheless of remarkable regularity."
VIII. Oxanthera Montrouzier
VIII. Oxanthera Montrouzier, Mém. Acad. Sci. Lyon 10:186. 1860.
Type species.—Oxanthera fragrans Montr.
Distribution.—New Caledonia and Art Island (80 km to the northwest of New Caledonia).
Common name.—False orange (or oxanthera).
Thornless small trees or shrubs with
thick but small 1-foliolate or simple leaves (3-10 cm long), usually
becoming glaucous; petioles either wingless or narrowly winged,
articulated with the leaf blade in 3 species, not articulated in the
other species; flower borne singly or in 1-3-flowered racemes in the
axils of the leaves; calyx and corolla 5-merous; stamens 3-4 times as
numerous as the petals; ovary with 2-7 locules, each locule containing
several ovules, usually 6; fruits ellipsoid, small, about 2.5 X 1.5 cm.
Oxanthera is a very distinct genus
of Minor Citroid Fruit Trees, subtribe Triphasiinae, and differs
strikingly from all the other genera of this subtribe in having
glabrous, glaucous leaves bluntly rounded or retuse at the tip and
cuneate at the base, borne on spineless twigs. The leaves
are thick and coriaceous in all the species except one. To
judge from the thick leaves that become glaucous as they develop, the
plants of this genus are very probably somewhat xerophytic, like Microcitrus of Australia, but are not so well adapted to withstand long-continued drought and hot, dry winds as the truly xerophytic Eremocitrus, also of Australia.
All the species of Oxanthera agree
in having large, orange-like flowers, and glabrous, more or less
glaucous leaves, which usually are rather blunt at the tip and cuneate
at the base. All species are thornless, and apparently all
have more or less elongate fruits that are longitudinally ribbed at
least when young. Probably no other genus except Poncirus in
the whole subfamily is so easily recognized at first
glance. In spite of this fact, this genus, containing four
species (see key)
shows unusual range of variation in other characters that in many
groups of plants are extremely constant and have high taxonomic
value. Three of the four species of Oxanthera have
unifoliolate leaves with clearly articulated petioles that are usually
wingless, but are plainly but narrowly winged in one
species. One of the species has a hypomerous ovary with only
two locules, another has an isomerous ovary with five or six locules,
whereas a third species has a hypermerous ovary with seven
locules. Better material of O. aurantium is urgently
needed to learn whether the ovary is always 2-locular; if so, it might
well be made the type of a subgenus. For the present it is
left in the genus as an anomalous species that, nevertheless, is clearly
related to the other three species.
It is probable that Oxanthera is a highly specialized xerophytic genus that has developed from the common ancestor of the genera Wenzelia and Monanthocitrus, both of which share with Oxanthera the character of having usually six ovules in each locule of the ovary. Oxanthera has acquired a distinctly xerophytic facies but, unlike the extremely xerophytic Eremocitrus, one of the True Citrus Fruit Trees of Australia, which has very small flowers, Oxanthera has large, white, fragrant flowers very like those of Citrus.
1. Oxanthera fragrans Montr. Mém. Acad. Sci. Lyon 10:186. 1860. Citrus oxanthera Beauv. Ann. Soc. Bot. Lyon 26:14. pro parte. 1901.
Type.—L'ile Art (about 80 km
northwest of the north end of New Caledonia) (Montrouzier).
Herb. Faculte de Méd. et Pharm. de Lyon.
Distribution.—Art Island, New Caledonia.
Common name.—Fragrant oxanthera.
The original description by Montrouzier,
translated, reads as follows: "Shrub 6-7 ft. [1.8-2.13 m] high,
beautiful, twigs terete, gray. Leaves obovate, apex
acuminate, subcrenulate, thick, very much dotted [with oil glands],
2-2.5 in. [5-6.3 cm] long (including the petiole), 6-7 lin. [1.2-1.4 cm]
wide. Peduncles axillary, 1-flowered, shorter than the
leaves. Flowers white, the size of those of Citrus Aurantium,
and very similar to them, very much dotted [with oil glands], exhaling a
penetrating odor. Fruit elongated. Is this Limonia lucida
Forst.? This beautiful shrub flowers in
November. It is found in the forest. The natives
call it Dongan na diet, 'Orange Tree of the Forest.' "
As the genus Oxanthera was originally monotypic, being founded on O. fragrans alone,
Montrouzier's description of the genus applies to the species as
well. It reads, translated, as follows: "Flowers 5-merous,
with imbricate aestivation, stamens 16-20, free. Anthers
erect, bilocular, incurved, mucronate at the apex. Fruit
with 5-6 locules, with many seeds in each locule. Style
elongate, thick, cylindric. Stigma obtuse.
Leaves 1-foliolate, articulated with the tip of the petiole, petioles
wingless. A spineless shrub."
Tanaka in discussing O. aurantium (1928b, p. 44) stated: O. fragrans has
petals clearly marked with translucent points, a glabrous calyx, oblong
anthers with only a small mucron at the apex, an oblong-oval ovary much
furrowed ['très creusé’], and a very short style." It
differs in all these points from O. aurantium, with which Beauvisage confused it, since he included descriptions of material of both species in his Citrus oxanthera. The
type specimen photographed by Tanaka shows petioles 4.5 to 7 mm long,
articulated with the leaf blade, entirely wingless but apparently with a
shallow channel on the upper side.
This plant is said to be a beautiful
fragrant shrub and may perhaps prove of value as an ornamental flowering
shrub for subtropical climates. To judge from its foliage,
it is probably somewhat drouth-resistant [sic]. The petals, with densely crowded oil glands, may possibly yield an essential oil for perfume.
2. Oxanthera aurantium Tan. Bul. Soc. Bot. France 75:712. 1928. Citrus oxanthera Beauv. Ann. Soc. Bot. Lyon 26:14. pro parte. 1901. Illus. Guillaumin, Les Citrus Cult. Sauv. 60. 1917.
Type.—New Caledonia, Gomonen near Gatope on dry hills (Vieillard, No. 2378). Herb. Mus. Hist. Nat., Paris.
Distribution.—Known only from the original collections.
Common name.—Orange flower oxanthera.
Tanaka’s original description reads, in
translation, as follows: "A shrub, twigs terete, very leafy, young twigs
pubescent; leaves small, oblanceolate, not glandular [?,
‘englandulosis’], chartaceous, channeled, with many veins, lateral veins
curved, arising from the midrib at more or less wide angles; apex
obtuse or often emarginate, base attenuated, short-petiolate; petioles
cylindric, not articulated [with the leaf blade]; inflorescences
pubescent, 1-3-flowered racemes; flowers large, equaling Citrus
in size, petals without oil glands, minutely papillose; calyx
scutellate, pubescent without, lobes rounded, inflexed; stamens free or
in part cohering, filaments much longer than the style, canaliculate,
minutely papillose on the outside, anthers rather large,
cordate-acuminate; ovary ovoid-attenuate, glabrous, style equaling the
ovary [in length], straight, cylindric, rather thick, stigma ellipsoid,
disk annular, short, stigma ellipsoid, broader than the style."
Swingle examined two cotypes from the
original type collection of this species (Vieillard, No. 2378), one in
the herbarium of the Museum of Natural History, Paris, and the other, an
excellent flowering specimen, in Gray Herbarium, Harvard University,
Cambridge, Massachusetts. The latter specimen shows
completely thornless twigs, pubescent when young but losing the hairs
and appearing glaucous with grey wax when older; leaves simple, thick,
coriaceous, oblanceolate, 2-4 X 0.5-1 cm, apex rounded, usually rather
deeply emarginate, margins minutely crenulate-dentate above the middle,
upper surface dotted with minute oil glands, about 0.5 mm apart, which
are not translucent on dry specimens, midrib slightly raised on the
upper surface, strongly salient below, slightly pubescent near the base
of the leaf, lateral veins visible only on the under surface, curved and
more or less swollen and salient, arising sometimes at an angle of
35°-45°, sometimes at an angle of 75°-80°, with the midrib, soon curved
backward toward the base of the leaf and anastomosing especially in the
upper part of the leaf; petioles pubescent, not articulated with the
leaf blade but merging imperceptibly into it, flattened above and
showing two raised lines that continue the leaf margins, running almost
to the base of the petiole, but showing no green color for 2-3 mm from
the base; peduncles at flowering densely covered with gray hairs, with
several leaf-like bracts, making the peduncle appear like a short leafy
twig; pedicel very short (3-4 mm), not clearly demarcated from the
calyx, which is densely gray-pubescent without; flowers like Citrus except for the gray-pubescent calyx and minutely papillose petals.
Tanaka (1928b, p. 712) noted that this species differs greatly from O. fragrans in
its pubescent new growth, narrower leaves with many lateral veins
arising at a wide angle with the midrib, and entirely different flower
parts. Beauvisage (1901, pp. 11, 12) studied several
specimens of Vieillard's No. 2378 (the type collection on which O. aurantium
is based) and his report, translated, reads as follows: "I dissected
several rather badly preserved flowers and found 14 to 16 stamens with
mucronate anthers and connate filaments except in a very young bud,
where the filaments, still short, were free. Similarly I
noted in the ovaries a few differences which could be due to the more or
less advanced stage of development; the ovary was ovoid or conical; the
style articulated [with the ovary] or not; the stigma
channeled-ellipsoid or not; the locules of the ovary, usually with
several ovules ('pluriovalées'), seem sometimes to be biovulate."
A good specimen of the type collection
(Vieillard's No. 2378) in the Gray Herbarium at Harvard University
provided a flower which Swingle examined. It was restored by
prolonged soaking, then imbedded, cut into serial sections, stained and
mounted permanently by a modification of Juel's method (see Swingle,
1939b, p. 270). The ovary was skillfully cut by
Swingle's assistant in this part of the work, Albert H. Tillson, so as
to show half the ovary cut into many serial longitudinal sections and
the remaining (longitudinal) half cut into still more numerous cross
sections. These sections showed clearly that the ovary was
cylindric, about 3.5 mm long after the dehiscence of the style, and 0.9
to 1.2 mm in diameter (with two shallow furrows in the plane of junction
of the carpels and two low ridges on the dorsal walls), narrowed
abruptly at the base and fitting rather closely into a conical cavity in
the top of the disk; it contained two long, slender locules about 2.4
by 0.3 by 0.4 mm. The ovary was narrowed gradually at the
top into the style, 0.5 to 0.6 mm in diameter at the point of
dehiscence. The serial cross sections showed altogether six
ovules in the locule, arranged in two ranks, along with abundant
trichomes arising from the flattened placenta that ran from bottom to
top of the locule cavity along its dorsal wall.
This species differs widely from its
congeners in having a hypomerous ovary with only two
locules. Of the other species, one is isomerous with five or
six locules and another is hypomerous with seven locules. O. aurantium
also differs radically from its congeners in having simple instead of
unifoliolate leaves. Its relationships are discussed above.
This species, collected by Vieillard on
arid hills in New Caledonia, shows signs of being a rather pronounced
xerophyte able to grow in dry situations. The thick leathery
leaves remind one of the leaves of Eremocitrus grown on
well-watered soil but are not so gray-green in color and show a
different structure on the upper and lower surface, a difference that is
almost lost in Eremocitrus.
3. Oxanthera undulata (Guill.) Swing. Jour. Wash. Acad. Sci. 30:83. 1940. Citrus undulata Guill. Bul. Soc. Bot. France 85:304. 1938.
Type.—New Caledonia, upper Dothio Valley (Balansa, No. 3054). Herb. Mus. Hist. Nat., Paris.
Distribution.—Known only from the type locality in northern New Caledonia.
Common name.—Wavy-leaf oxanthera.
The original description of this species
reads, translated, as follows: "Tree 5-6 m high, very glabrous; leaves
thin, ovate-lanceolate, up to 9 X 4 cm, cuneate at the apex and base,
with undulate margins, nerves very slender, almost immersed, petiole
articulated [with the lamina], slender, 5-10 mm long, [wingless and] not
at all margined; flowers not seen; fruits ovate, 2.5 X 2 cm, embryo
with white cotyledons…"
The notes which follow the Latin
diagnosis read: "Excessively rare; a species well characterized,
although imperfectly known, by its thin leaves with strongly undulate
margins. The fruit resembles that of C. neo-caledonica in form." Unfortunately the number of locules in the fruit is not stated.
To judge from its large thin leaves, this
species may perhaps prove to be a mesophyte rather than a xerophyte, as
are the other 3 species in Oxanthera.
4. Oxanthera neo-caledonica (Guill.) Tan. Bul. Soc. Bot. France 75:713. 1928. Citrus neo-caledonica Guill. in Lecomte, Not. Syst. 2:130 (diagnosis). 1911; and ibid. 2:390 and 406 (Latin name).5 1913. Illus. Guillaumin, Les Citrus Cult. Sauv. 61. 1917; fig. 3-12 this work.
Type.—New Caledonia, Poume Peninsula (Balansa, No. 3374). Herb. Mus. Hist. Nat., Paris. Cotype: Same collection (Balansa, No. 3374). Herb. Bur. Sci., Manila.
Distribution.—Known only from the type locality (Lat. 20° 30' S., Long. 164° 8' E.).
Common name.—False orange (or large-leaf oxanthera).
Guillaumin's detailed description of this
plant reads, in translation, as follows: "Spineless shrub, 1 m high,
with whitish flowers; young branches with a waxy bloom that gradually
disappears. Leaves very coriaceous, glabrous even when very
young, lanceolate or obovate, 6-8 cm long (including the petiole), 1-4
cm wide, narrowed toward the base, attenuate toward the apex, but not
acute when lanceolate, suborbicular or orbicular when obovate, sometimes
emarginate. Midrib and lateral veins prominent on both
sides but especially on the underside (like veins of the
hand). Petiole distinctly articulated [with the leaf blade],
1-2 cm long, slightly winged (less than 4 mm). Flower [bud]
(a single one) terminal on a young branch, spherical (14 mm diam.);
pedicel 7 mm long, cylindric, glabrous; sepals 5, 2 mm long, nearly
round; petals 6, unequal, ovate (12 X 6-12 mm), thick and fleshy, with
inconspicuous, small, pellucid oil glands; stamens 24, unequal (8-11
mm), [arranged] very irregularly in fascicles, filaments rather fleshy,
not flattened, anthers triangular-elongate, 2.5 mm long, the locules
diverging slightly at the base; ovary subcylindric (3.5 X 3 mm),
7-ribbed, with 7 segments; style cylindric, 2 mm long, stigma
cylindric. Fruit (immature) ovoid-subcylindric, supported on
pedicels covered with whitish bloom, more than 1.5 cm long and 2 mm
diam.; more mature fruits 2.5 X 1.5 cm, with 7 segments, peel thin, pulp
mucilaginous, seeds of unknown color.
"Presqu'ile de Poume, in volcanic soil, May, 1871 (Balansa, No. 3374).
"Although the color of the embryo is not
known, the affinities [or this plant] seem to be especially with Citrus Aurantium L. but the form and the aspect of the leaves, of the flowers and of the ovary, clearly distinguish this species."
Tanaka (1928b, p. 44) noted that the flowers are like those of O. fragrans and O. aurantium
but that "the surface of the petals is completely uniform [not
papillose or marked with evident oil glands], the ovary is shorter, the
stigma not dilated and the disk much larger." He went on to
say: "The fruit is oblong, sometimes curved, pointed, with superficial
ribs, with about 7 segments, containing large seeds with a single very
hard embryo. The pulp-vesicles are not very much developed
and are gummy." He was of the opinion that the lack of true
pulp-vesicles excludes this species from the True Citrus Fruit Trees
even though it does have more than twice as many stamens as petals.
This species, as Tanaka remarked, shows a
higher organization than most of the other Minor Citroid Fruit
Trees. It has seven locules in the ovary and, in common with
the other species of Oxanthera, more than twice as many stamens
as petals, instead of only twice as many, as is characteristic of the
other genera of the subtribe Triphasiinae.
IX. Merope Roem.
IX. Merope Roem. Syn. Hesper. 1:44. 1846.
Type species (Monotype).—Citrus angulata Willd. = Merope angulata (Willd.) Swing.
Distribution.—Java, Burma; also New Guinea (fide Tanaka, 1931b, p. 10).
Small tree, twigs with stout spines
paired or single; leaves simple, thick, coriaceous; petioles short,
wingless; flowers solitary, axillary; calyx cupulate, 5-lobed; petals 5,
imbricate, oblong-lanceolate, acute; stamens 10, free, anthers linear,
as long or longer than the filaments; ovary ovoid, 3-locular, ovules 4
in each locule; fruit triangular in cross section, ovoid-acuminate, with
very long, flattened seeds narrowed at the upper end to a blunt point,
borne 1 in a segment and immersed in a glutinous, mucilaginous fluid.
This remarkable genus is found widely
scattered over the East Indies in brackish swamps. It is
outstanding because of its buckwheat-shaped fruit, containing very long
seeds. It is a highly specialized genus of the subtribe
Triphasiinae, related to Pamburus and Paramignya, but not closely.
Merope angulata (Willd.) Swing. Jour. Wash. Acad. Sci. 5:420. 1915. Citrus angulata Willd. Sp. Pl. ed. 4. 3(2):1426. 1801; Limonellus angulosus Rumph. Herb. Amboin. 2:110. 1741; Sclerostylis spinosa Blume, 1825; Glycosmis spinosa (Bl.) Dietr. 1840; Merope spinosa (Bl.) Roem. 1846; Limonia angulosa Wt. & Arn. ex Miq. 1859; Atalantia longispina Kurz, 1872; Gonocitrus angulatus (Willd.) Kurz, 1874; Paramignya angulata (Willd.) Kurz, 1875; Atalantia spinosa (Bl.) Koorders (non Hook. f.), 1912; A. angulata (Willd.) Engl. Die Nat. Pflanzenfam. 19a:330. 1931. Illus. Rumphius, loc. cit. pl. 32; Kurz, Jour. Asiat. Soc. Bengal 43(2):pl. 18. 1873; Valeton, Icon. Bogor. pl. 348. 1912; Swingle, loc. cit. figs. 1-2; idem, in Bailey, Stand. Cycl. Hort. 4:2038, fig. 2362. 1916; idem, in Engler, loc. cit. 329, fig. 151; fig. 3-13 this work.
Type.—None found; based on Rumphius' description and figure cited above.
Distribution.—Java, Burma, in tidal swamps; also New Guinea (fide Tanaka, 1931b, p. 10).
Common name.—Merope (or kigerukkan, so-called at Noessa Kambangan Island, Java).
Leaves coriaceous, inconspicuously
veined, alternate; petioles simple. Twigs with very strong
spines, often in pairs. Flowers borne singly or in pairs
(rarely in few-flowered clusters) in the axils of the leaves; ovary
stalked on a rather tall disk, 3-5-celled, with 4 pendulous ovules in
each cell; stamens 10, free, anthers linear-oblong. Fruits
strongly angled, triangular in cross section; cells filled with a
sticky, mucilaginous fluid (without true pulp-vesicles); seeds very
large, flattened, reniform, caudate at the tip where
attached. Cotyledons in germination aerial, not increasing
in size; first foliage leaves alternate, broadly ovate. A
large shrub or small tree (not a climbing shrub), growing on the
seashore in tidal forests or mangrove swamps from the mouth of the
Ganges to the Moluccas. The seeds, often 2 in each of the
flattened locules of the fruit, are about 35 X 15 X 5 mm, largest known
in the orange subfamily.
This remarkable plant, the sole species of the genus Merope,differs strikingly from all other species of the orange subfamily except Severinia lauterbachii in
having fruits triangular in cross section, with long flat seeds
tapering to a blunt point. It is a very spiny salt-loving
shrub or small tree found in tidal marshes in Java and Burma, and in the
East Indian Archipelago. As is usual with halophytes
(plants able to live in more or less salty water), M. angulata has thick and leathery leaves. Buds of the kigerukkan,
inserted on grapefruit, grew vigorously in the greenhouse of the former
Bureau of Plant Industry at Washington, D.C., and soon flowered (see fig. 3-13), but finally showed signs of a bad bud union, became stunted, and died.
GROUP B. THE TRIPHASIA GROUP
This group contains two genera with a
total of four species, all of them shrubs or small trees with small
ovoid or globose fruits, bright-colored (red) in Triphasia and orange-like with a thick peel dotted with oil glands in Pamburus,
but always without pulp-vesicles in both genera. The
ovaries are 3- to 5-locular, and each locule contains one or two
ovules. The leaves are simple in two of the species of Triphasia, as well as in Pamburus, and trifoliolate in the other species of Triphasia;
they are rather thick, more or less glaucous, and inconspicuously
veined. Little is known as yet about the relationships of
these two genera with the other genera in the subtribe Triphasiinae.
X. Triphasia Lour.
X. Triphasia Lour. Fl. Cochinch. 152. 1790. Echinocitrus Tan. Jour. Arnold Arbor. 9:137. 1928.
Type species.—Triphasia aurantiola Lour. = T. trifolia (Burm. f.) P. Wils.
Distribution.—Southeastern Asia, East Indies, Philippines, New Guinea; widely cultivated in tropical and subtropical regions.
Common name.—Limeberry (or triphasia).
Shrubs or very small trees, 1-2 m high,
with paired axillary spines; leaves usually very small (except in T. grandifolia),
simple or 3-foliolate, rather thin and without evident reticulation,
numerous oil glands visible on both faces; petioles very short
(1/10-1/20 the length of the leaves), wingless, pubescent, flattened and
slightly channeled on the upper surface, not articulated with the leaf
blade; flowers single, or in groups of 2 or 3 in the axils of the
leaves; pedicels slender; calyx 3-5-merous, cupulate, persistent;
corolla 3-5-merous, petals linear or obovate-spathulate; stamens free,
twice as many as the petals, filaments slender, sometimes broadened at
the base, anthers small, linear; ovary ovoid or elliptical, tapering
more or less toward the base, with 3-5 locules, ovules 1 or 2 in each
locule; fruits small, with the seeds imbedded in mucilaginous pulp;
seeds plump (sometimes polyembryonic in T. trifolia).
The genus was represented from 1790 until 1925 by a single species, T. trifolia. The discovery in the Philippines of a second species, a plant with much larger simple leaves which Merrill named Triphasia grandifolia, broadened our concept of the genus.
It now appears that there is a third species, descried as Paramignya brassii from New Guinea by C. T. White in 1926 and made the type of a new genus, Echinocitrus, by Tanaka in 1928. This species, although obviously closely related to the type of Triphasia, differs in a number of characters that justify placing it in a distinct subgenus, for which Tanaka’s generic name, Echinocitrus, is retained.
Keys to the subgenera and species of Triphasia are presented.
Subgenus Triphasia
Subgenus Eutriphasia Swing. in Webber & Batchelor, Citrus Indus. 1:237. 1943.
1. Triphasia trifolia (Burm. f.) P. Wils. Torreya 9:33. 1909. Limonia trifolia Burm. f. Fl. Ind. 103. 1768; L. trifoliata L. 1771; Triphasia aurantiola Lour. 1790; Limonia (?) diacantha DC. 1824; Triphasia trifoliata (L.) DC. 1824. Illus. Burmann f. loc. cit. pl. 35 (col.); Jacquin, Icon. Pl. Rar. 3:pl. 463. 1786-1793; Risso & Poiteau, Hist. Nat. Orang. pl. 108 (col.). 1818-1822; fig. 3-14 this work.
Type.—Java (Burmann f., No. 166). Herb. Delessert, Geneva (fide Tanaka).
Distribution.—Southeastern Asia (?), East Indian Archipelago (?); widely cultivated in tropical and subtropical regions.
Common name.—Trifoliate limeberry, limeberry, or triphasia.
A glabrous shrub or small tree with
terete twigs bearing paired spines in the axils of the leaves; leaves
3-foliolate, the terminal leaflet ovate with a cuneate base and a
rounded emarginate tip, 2-4 X 1.5-2 cm; lateral leaflets much smaller
than the terminal one (1-2-2 X 0.8-1.2 cm), broadly rounded at the tip,
cuneate at the base; petiolules very short (1.5-2 cm); petioles short
(3-5 mm), wingless; flowers appearing singly or 2 or 3 in the axils of
the leaves; peduncles short (3-4 X 1 mm); flower buds cylindrical, 10-12
X 3-4 mm; flowers 3-merous (but with 6 stamens); sepals small (1.5-2 mm
long), 3-lobed, green, persistent; petals white, 10-13 X 3.6-4.5 mm;
staminal filaments slender, glabrous, 9-11 mm long, anthers oblong, 2 X 1
mm; disk annular or short-cylindric; ovary ovoid or fusiform with 3
locules, each with 1 ovule, narrowed into a slender, deciduous style
with a capitate, 3-lobed stigma; fruit ovoid or subglobose, sometimes
apiculate, 1.2-1.5 cm long, dull reddish-orange or crimson when fleshy
ripe; peel with many small oil glands; seeds 1-3, immersed in
mucilaginous pulpy flesh.
Triphasia trifolia is very widely
grown in all tropical and subtropical regions as an ornamental
shrub. It is also used for hedges. The fragrant
white flowers are soon succeeded on the branches by the small dull-red
berries (see fig. 3-14).
The foliage is handsome, a shiny dark green, and the plant usually
makes a round-topped shrub that does not grow too large for dooryard
plantings. Triphasia trifolia has become naturalized
in certain sections of the United States, in "hammocks, fields and
cultivated grounds, coastal plain, Florida to Texas," according to Small
(1933, p. 760).
la. Triphasia trifolia forma tetraploidea.
This form differs from the species in
having larger flower parts and thicker leaves, and especially in having
36 chromosomes in all the somatic cells instead of 18, the normal number
for almost all plants of the orange subfamily so far studied.
This undoubtedly tetraploid form of the common trifoliate limeberry is like tetraploid forms of Citrus in
having somewhat thicker leaves and larger flower parts.
Longley (Traub and Robinson, 1937, p. 794) first detected the tetraploid
nature of this plant. It is one of a number of seedlings
(of which all the others are apparently diploid) grown from seeds of Triphasia trifolia
collected by Dr. J. N. Rose at Mazatlan, Mexico, in April,
1910. This is believed to be the first instance reported of
the spontaneous origin of a tetraploid seedling of an aurantioid genus
other than Citrus or Poncirus. It is analogous to the wild-growing tetraploid form of Fortunella hindsii, native to the mountains of southern China, of which a diploid form is found in cultivation. Frost (1938a) has found tetraploid mutations of several of the commonly grown species of Citrus arising as seedlings in California.
2. Triphasia grandifolia Merr. Phil. Jour. Sci. 26(4):458. 1925.
Type.—Mindoro Island, P.I. (Ramos, No. 40822). Herb. Bur. Sci., Manila.
Distribution.—Philippines: known only from the type locality.
Common name.—Unifoliate limeberry.
Merrill's description of this species
reads as follows: "An erect, nearly glabrous, spiny shrub about 2 m
high, the branches and branchlets slender, terete, pale greenish when
dry, the branchlets 1 to 1.5 mm in diameter, puberulent.
Leaves simple, alternate, chartaceous, oblong-ovate, 5 to 9 cm long, 2.5
to 4.5 cm wide, greenish when dry, the base broadly rounded, narrowed
upward to the somewhat acuminate apex, the lower surface paler than the
upper and conspicuously glandular-punctate; lateral nerves slender,
spreading, about 10 on each side of the midrib; petioles about 3 mm
long; stipules spiniform, rigid, stiff, 5 to 7 mm long.
Flowers white, solitary, axillary, one between each pair of spinelike
stipules, their pedicels about 6 mm long, somewhat thickened
upward. Calyx 4 mm in diameter, the tube 1 to 1.5 mm long,
the three broad triangular lobes obtuse to acute, punctate, about 2 mm
long. Petals 3, imbricate, glabrous, punctate,
oblong-oblanceolate, about 1.5 cm long, 0.5 cm wide. Stamens
6, their filaments narrowly lanceolate, tapering upward, 7 mm long,
anthers oblong, 3 mm long. Ovary 3 celled, short-stipitate,
oblong, slight thicker than the stout stipe and style, glabrous, the
style 6 mm long, stigma subcapitate. Disk truncate, about 1
mm high. Fruits unknown."
Triphasia has been known since 1790 as a monotypic genus, T. trifolia,
the type species, was remarkable in having three sepals, three petals,
six stamens (three alternating with the sepals and three with the
petals), an ovary with three locules, and trifoliolate leaves, so the
genus name, Triphasia, was unusually appropriate. In
1925, Merrill received from Mindoro Island in the Philippines a second
species, clearly a Triphasia, with 3-merous flowers as in T. trifolia but
with large simple leaves instead of small trifoliolate
leaves. The fruits of this interesting species are still
unknown.
Subgenus Echinocitrus (Tan.) Swing., n. comb.
3. Triphasia brassii (White) Swing. Jour. Wash. Acad. Sci. 28:532. 1938. Paramignya brassii C. T. White, Jour. Arnold Arbor. 7:231. 1926; Echinocitrus brassii (White) Tan. Jour. Arnold Arbor. 9:138. 1928.
Type.—New Guinea, Papua, Rigo (Brass, No. 817). Herb. Arnold Arbor.
Distribution.—New Guinea: known only from the original locality.
The original description of Paramignya brassii (= Triphasia brassii) by C. T. White, translated, reads as follows: "A slender bush, attaining 2 m in height, branches drooping (fide
Brass); spines numerous, single or paired, 0.8-1.5 cm long, slender,
puberulous, evanescent on fast-growing large shrubs; leaves shiny, dark
green (fide Brass), with short petioles; petioles puberulous, 2-3
mm long; varying greatly in the size of the blade, on flowering twigs
small (1.5 X 0.8 cm), usually larger (4 X 3 cm), ovate-rhomboid,
retusely acuminate at the apex, lateral veins 5-6 pairs, visible above
and below; flowers sweet-scented (fide Brass), axillary,
solitary, with a glabrous peduncle thickened toward the apex, about 1 cm
long; calyx 5-lobed, lobes broadly deltoid, about 1 cm long, margins
ciliate; petals 5, obovate, 1 X 0.3 cm, with numerous oil glands outside
toward the tip; stamens 10, filaments free, 6 mm long, anthers linear, 2
mm long; ovary lageniform, short-stipitate; stipe in dried specimens
slightly ribbed; style thick, ribbed, 5 mm long, stigma discoid; fruit
red, of variable form, ellipsoid, pyriform or obovoid, 3 cm long, 1.5-2
cm diam., 5-locular, pulp scanty, seeds 1 or 2 in each locule, 1 X 0.6
cm."
The simple crenate leaves of the type
material of this species are usually broad at the base, often nearly
trangular [sic] in outline.
In discussing this plant, which he made the type of a new genus, Echinocitrus, Tanaka (1928c, p. 138) wrote: "…the present species is closely allied to Triphasia in
its puberulent, somewhat zigzag branches armed with paired sharp
spines, in the thin leaves without prominent reticulation, solitary
flowers with cupulate calyx and slender petals, free filiform filaments
and linear anthers, stalked ovary narrowed into a long style, and in the
few-celled bright-colored berry without pulp-vesicles. It
is, however, distinct from Triphasia primarily in having 5-merous flowers, while both species of Triphasia (T. trifolia and T. grandifolia) have always 3-merous flowers. This species is far more spiny than Triphasia,
especially at the juvenile stage, and the fruit is very much larger and
mostly pointed at the base, not at the apex, the segments containing
distinctly biseriate seeds. The leaves are crenate, not
entire, and the pedicel of the fruit is very much elongated; calyx lobes
are distinct and ovoid-deltoid, not so broad and flat-triangular as in Triphasia. The
calyx lacks pubescence but is only minutely ciliate on the
margin. The appearance of the fruit is very much like an
oval kumquat (Fortunella margarita Swingle), but it lacks pulp-vesicles."
The characters mentioned above are most
of them of specific rather than generic nature. The fact
that this species is 5-merous (except that the stamens are twice as many
as the petals) is not an adequate character to separate it as a
distinct genus from T. trifolia and T. grandifolia, both
of which have 3-merous flowers (except the stamens, which are
6-merous). Such variation in the number occurs frequently in
genera belonging to the subtribe Triphasiinae, of which Triphasia is the type genus.
XI. Pamburus Swingle
XI. Pamburus Swingle, Jour. Wash. Acad. Sci. 6:336. 1916. Chilocalyx Turcz. (non Klotzsch), Bul. Soc. Nat. Mosc. 36:588. 1863. Illus. Wight, Hook. Bot. Misc. 3:291, pl. 33. 1833; fig. 3-15 this work.
Type species.—Limonia missionis Wight = Pamburus missionis (Wight) Swing.
Distribution.—India: Madras State; Ceylon; Vietnam: Annam, Cochin China; Java; Bali.
Common name.—Pamburus.
Much-branched, very thorny shrubs or
small trees, young twigs angled, soon becoming terete; leaves simple,
very thick; petioles short, less than 1/10 the length of the leaf blade,
more or less margined but not winged, not articulated with the leaf
blade; inflorescences axillary racemes shorter than the leaves but
longer than the petioles; flowers 4- or 5-merous; calyx cupulate,
4-5-lobed; petals 4 or 5, obovate or elliptic-oblong; stamens 8-10
(twice as many as the petals), filaments free, slender, glabrous,
anthers cordate-elliptical or linear-oblong; disk cylindric, narrower
than the ovary; ovary with 5 (or sometimes 4) locules, with 2 ovules in
each locule; fruits globose (resembling a very small orange in
appearance), with a well-developed peel showing numerous oil glands, the
segments usually containing 1 or 2 seeds surrounded by a glutinous
mucilage (pulp-vesicles lacking); seeds large, thick, globose or ovoid.
Pamburus differs from Paramignya
in its shrubby habit and lack of retrorse or hooked spines, and in its
thick leaves with rounded tips and short non-articulated petioles
without pulvinoid tips. Its relationships to the other
genera of the subtribe Triphasiinae are still obscure and should be
cleared up by a detailed study of the flowers and fruits.
Pamburus missionis (Wt.) Swingle, Jour. Wash. Acad. Sci. 6:338. 1916. Limonia missionis Wt. Hook. Bot. Misc. 3:291. 1833; Atalantia missionis (Wt.) Oliv. 1861; Chilocalyx ellipticus Turcz. 1863. Illus. Wight, loc. cit. pl. 33; fig 3-15 this work.
Type.—British India, Madras Presidency, Talaar (Wight in Wallich, No. 6358-B). Herb. Kew.
Distribution.—India.
Common name.—Pamburus.
The original description by Wight reads
as follows: "Leaves simple, elliptical-oblong, short-petioled; racemes
many-flowered, in the axils of the spines, shorter than the leaves.
"A small tree, with a round, very branching, bushy head; the branches round, smooth, bright green, the older ones armed with numerous large, strong, sharp thorns, the flower-bearing ramuli flexuose, with small, straight, axillary spines. Leaves
alternate, short-petioled, oval, sometimes emarginate and slightly
crenate, oftener entire, smooth, coriaceous, dark shining green, mottled
with white spots, and perforated with numerous pellucid
points. Racemes in the axils of the spines, shorter than the leaves, somewhat capitate. Flowers numerous, fragrant, pure white. Calyx small, 4- or 5-lobed. Corolla 4-5-petaled, caducous. Petals obovate. Stamens 8 or 10, a little shorter than the petals. Filaments subulate. Anthers erect, large in proportion to the flowers. Pistil: germen superior, elevated on a glandular receptacle, globular, 4- or 5-celled, with several ovules in each cell, only one of which usually arrives at maturity. Style cylindrical. Stigma capitate. Pericarp a 4- or 5-celled berry; cells containing a very glutinous mucilaginous fluid, and one roundish seed,enclosed in a thick, firm, glandular, orange-like fruit.
"This tree is found, rather frequently,
in sandy soil near the sea-coast, flowering towards the end of the cool
season, and ripening its fruit about August or September.
The corolla falls a few hours after expansion; hence it is
difficult to procure specimens in flower. That here figured
was gathered about the beginning of March."
Swingle's description of the species given when the genus Pamburus was established (1916a,
p. 338) reads as follows: "A much-branched shrub or small tree, armed
with stout straight spines, these 2-3 cm long, arising singly (or rarely
in pairs?) on the side of the bud in the axils of the
leaves. Leaves oval, oblong-obovate or elliptical, 6-10 cm
long, 2-4 cm broad, very thick, coriaceous, glandular-punctate, the tip
rounded, sometimes slightly emarginate, the base narrowed rather
abruptly into the petiole, the margin entire, becoming gray and
apparently crenate in drying; lateral veins inconspicuous, tertiary ones
not apparent, the two faces very similar in appearance, drying to
velvety gray-green unlike those of any other member of the subfamily
Citratae [Aurantioideae]. Flowers 12-20 mm in diameter,
fragrant, with small pointed sepals and 5 or 4 white obovate caducous
petals about 1 cm long. Pistil about 1 cm long.
Fruit about 2.5 cm in diameter, orange-colored when ripe, with a thick
peel dotted with oil glands, 5-4 celled, the cells containing 1 or 2
seeds surrounded by a sticky gum."
This remarkable plant has leaves unlike those of any other member of the orange subfamily (see fig. 3-15).
In drying they become pale gray-green and show what seems to be a
fine-textured, velvety surface. As it grows commonly in the
dry region of Ceylon and in the flat, sandy coastal lands of Madras
State in India, it may prove to be the fourth genus of the orange
subfamily to show somewhat xerophytic structure, the other three being Oxanthera of New Caledonia, and Microcitrus and Eremocitrus, both of the semiarid regions of northeastern Australia.
The wood of P. missionis is used in India for making furniture. The species should be tested as a rootstock for Citrus with Oxanthera fragrans and Eremocitrus glauca in the hope of finding rootstocks able to grow in soils with heavy content of mineral salts. Pamburus missionis was introduced into the United States several decades ago.
In 1941, a five-year-old tree of this
species growing at the Plant Introduction Garden in Coconut Grove,
Florida was about 2.5 meters high and 1.5 to 2 meters wide, with a very
dense top composed of exceedingly numerous, short, divergent, very leafy
twigs with stout, very sharp spines, 1.5 to 4 cm long, attached nearly
at right angles to the twig every 2 to 4 cm. The younger
branches, the spines, and the more or less exposed under surfaces of the
leaves were all of the same vivid green color, close to grass green
(Ridgeway, 1912, pl. 17). The upper surfaces of the leaves,
also visible in large part, were a slightly darker green, near Hay’s
green (Ridgeway, 1912, pl. 6). The foliage was not only
vivid green, but perfectly smooth and glossy, and showed no traces of
injury from insects or diseases. This plant seems admirably
suited for making beautiful hedges of moderate height, since it stands
pruning well.
Anatomical study of freshly gathered
leaves shows that the upper surfaces have two layers of palisade cells
and the under surface one layer. This doubtless explains the
almost identical appearance of the upper and lower surfaces of the
leaves and the almost complete masking of the veinlets.
The plants grown at Coconut Grove thrived
on rather poor, sandy soil that thinly covered a subsoil composed of
porous limestone rock. The pamburus seems to withstand
nearly as much cold as the commonly cultivated species of Citrus.
GROUP C. THE LUVUNGA GROUP
The two closely related genera Luvunga and Paramignya,
with a total of twenty-seven species, are both clambering woody lianas
that hold fast to the branches of trees by means of retrorse or
sometimes strongly recurved spines. The leaves of Luvunga are large, apparently palmately trifoliolate, with very long wingless petioles; those of Paramignya
are medium-sized, unifoliolate, with short petioles. Both
genera have the petioles articulated at both ends (at the junction with
the leaf blade above and with the twig below). These joints
at both ends of the petioles are more or less swollen and pulvinoid,
which permits each leaf to take up the best possible position to catch
the light. The ovaries are 2- to 5-locular and each locule
has two ovules. The fruits, so far as known, do not contain
pulp-vesicles.
The fruits both of Luvunga and of the typical species of Paramignya
show a striking dimorphism of the oil glands, those in the peel being
small, those in the deeper tissues between the peel and the locule
cavities being much larger. Possibly the deeper glands may
produce not oil but mucilage that ultimately flows into the locule
cavities about the seeds as the fruits ripen. Only the study
of fresh living fruits can decide the matter.
It is highly probable that Luvunga and Paramignya are descended from a common ancestral plant with pinnate or trifoliolate leaves. When Luvunga
plants bear unifoliolate leaves, they have very much shorter petioles
than do the normal trifoliolate leaves and, in consequence, look much
like normal Paramignya leaves. The flowers of both Luvunga and Paramignya look much like those of Citrus except for having fewer stamens (only twice as many as the petals instead of the four or more times as many found in Citrus). The fruits look much like miniature lemons or limes, and, like ordinary Citrus fruits, have a peel thickly dotted with oil glands.
Abundant material of the genera Luvunga and Paramignya
studied by Tillson (1938, pp. 11, 12, 24) shows that in the development
of the flower the petal midrib, as it diverges from the axis, carries,
fused with it, the lateral sepal traces, an unusual type of floral
vascular anatomy, characteristic of the Primitive Citrus Fruit Trees of
the subtribe Citrinae, of the species of the subgenus Citrus (comprising all the commonly cultivated citrus fruit trees), and of Swinglea (see Tillson and Bamford, 1938, p. 791).
It is possible that more thorough study of the developing fruits will show that Luvunga and Paramignya are
so closely related to the Primitive Citrus Fruit Trees that they should
be transferred out of the subtribe Triphasiinae to the subtribe
Citrinae. In the meantime, as the highest group (C) of the
Minor Citroid Fruit Trees, the Luvunga group is placed next to the Primitive Citrus Fruit Trees (group A) of the subtribe Citrinae.
XII. Luvunga Buch.-Ham.
XII. Luvunga6 (Lavanga) Buch.-Ham. Wall. Cat. 217. 1831; Wt & Arn. Prodr. 1:90. 1834. Lampetia Roem. Syn. Hesper. 1:42. 1846.
Type species.—Luvunga scandens (Roxb.) Buch.-Ham.
Distribution.—India, Ceylon, Burma, Thailand, Indo-China, Malay Peninsula, Sumatra, Java, Borneo, Philippines, and New Guinea.
Common name.—Trifoliate liana-limes (or luvunga).
Woody lianas with single, recurved
axillary spines; leaves 3-foliolate with long, wingless petioles;
leaflets oval to lanceolate, acute or acuminate at the apex, entire,
often slightly revolute on the margins; inflorescences dense axillary
racemes or panicles; flowers 4- or 5-merous; calyx cup-shaped, 4-5
lobed; petals 3-5, linear or lanceolate, thick; stamens 6-10 (rarely
fewer), with free, or more or less connate, filaments and linear
anthers; ovary elongate-ovoid, seated on a columnar gynophore, locules
2-4, with 2 collateral or superimposed ovules in each locule; style
gradually merging with the ovary, thick, sooner or later caducous,
stigma capitate; fruits ellipsoid or globose, rind thick; seeds 1-3,
imbedded in mucilaginous matter (pulp-vesicles not present!).
Luvunga includes about twelve
species which are very similar in general appearance. All
the species are woody vines that cling to forest trees by means of
strong, recurved spines in the axils of the leaves. They
also agree in having trifoliolate leaves (occasionally unifoliolate or
difoliolate), borne on very long, wingless petioles, and in bearing
crowded clusters of strongly but agreeably scented, white, orange-like
flowers in the leaf axils. The fruits are small, globose or
ovoid, usually rough-skinned, and yellow in color; they somewhat
resemble miniature lemons or oranges in appearance but contain no
juice. Instead they are filled with a sticky mucilaginous
substance in which the few medium-sized seeds are imbedded.
The species of Luvunga are
difficult to distinguish from a study of herbarium specimens and need
critical study badly. Only ten species are well enough known
to be keyed
out here, but two more of doubtful validity are added. Few
genera in the orange subfamily show so little diversity among the
species as does Luvunga, but this genus is not closely related to any other of the Minor Citroid Fruit Trees except Paramignya, which is also a genus of woody vines that hold fast to the branches of trees with their reflexed spines. Luvunga differs from Paramignya
chiefly in having an unusual type of trifoliolate leaves on long, stiff
petioles. Occasionally unifoliolate leaves with short
petioles are produced by species of Luvunga; such leaves bear a close resemblance to the characteristic leaves of Paramignya. It is possible, even probable, that the genus Paramignya arose from an aberrant species of Luvunga which produced only unifoliolate leaves.
The fruits of Luvunga show almost exactly the same structure as those of Paramignya.
They have small oil glands in the peel and much larger ones in the
tissue between the peel and the locule cavities. This
dimorphism of the oil glands (possibly oil glands and mucilage glands?)
is very evident in fruits of L. sarmentosa growing in the Botanic
Garden at Buitenzorg, Java, collected by C. S. Sargent, October 16,
1903, now in the herbarium of the Arnold Arboretum (Tanaka, Det. No.
A-325), and in L. crassifolia collected in Sumatra by H. S. Yates
(No. 254) in 1922, now in the herbarium of the University of
California, sheet 226,095 (Tanaka, Det. No. C-254).
All the species of Luvunga are
woody vines that clamber high on trees of tropical evergreen
forests. The fruits are small, 1 to 3 cm in diameter,
globular or lemon-shaped, with a rough peel and a few medium-sized
seeds. These luxuriant vines, bearing thousands of densely
crowded, fragrant white flowers, may prove useful as ornamentals in
southern Florida, Puerto Rico, and other rainy tropical regions.
1. Luvunga scandens (Roxb.) Buch.-Ham. Wall. Cat. 6382. 1831. Limoniascandens Roxb. Fl. Ind. 2:380. 1832. Illus. Hooker, Bot. Mag. 86:pl. 4522 (col.). 1850; Paxton, Fl. Gard. 1:109. 1850-1851; Lemaire, Jard. Fleuriste 1:pl. 75 (col.). (copied exactly from Hooker, loc. cit.) 1851; Schnizlein, Iconogr. 3:pl. 224. 1857-1865; Pierre, Flore Forest. Cochinch. 4:pl. 288A. 1893; Guillaumin, in Lecomte, Fl. Gén. Indo-Chine 1:667, fig. 71(1-2). 1911; Basu, Ind. Med. Pl. pl. 194. 1918; fig. 3-16 this work.
Type.—British India, hills about Silhet (Roxburgh). Herb. Hort. Bot., Calcutta.
Distribution.—India, Burma, Laos, North Vietnam, South Vietnam, Thailand; also occurs in Sumatra and Borneo (fide Tanaka).
Common name.—Indian liana-lime (or luvunga).
Twigs with long, acute, slightly recurved
thorns; leaves variable; petioles 5-13 cm; leaflets slender,
elliptic-oblong or oblanceolate, acute or acuminate at the tip, cuneate
at the base, venation inconspicuous; inflorescences small, axillary
cymes; flowers about 1.5-2 cm diam.; calyx with 4 short, truncate lobes;
petals 4, white, fleshy, recurved, 12.5-18 mm long and 2-6 mm wide;
stamens 8, glabrous, with the filaments connate nearly to the tips;
ovary with 3 or 4 locules, ovules 2 in each locule; fruits oblong, about
25 X 20 cm ("size of a pigeon's egg"), rather smooth; seeds oval,
somewhat pointed, integument thin, monoembryonic cotyledons oblong,
green.
This, the type species of the genus, is
easily recognized by the smooth, entirely hairless staminal filaments
that are fused together nearly to their tips into a tube and by the
long, slender, pointed leaflets. It is native from
northeastern India through northern Burma, Laos, Cambodia, and North and
South Vietnam. Luvunga scandens is the best-known
species of the genus, as it has been very well illustrated by Hooker and
Pierre. It can be easily grown in a greenhouse but,
according to experiences in Europe, it does not flower unless given
opportunity to climb high, as, for instance, in a palm house.
2. Luvunga crassifolia Tan. Med. Rijks Herb. Leiden 69:8. 1931.
Type.—Malacca (Maingay, No. 285). Herb. Kew.
Distribution.—Malay Peninsula, Borneo, Sumatra.
Tanaka's original description,
translated, reads as follows: "Branches thick; spines curved; petioles
short, somewhat thick; leaves very thick, obovate or oblong-obovate,
rounded at the apex, frequently emarginate, often apiculate, obtuse at
the base, margins slightly revolute, shiny above, with distinct veins,
dull below, minutely verrucose. Inflorescence many-flowered;
flowers large; calyx deeply cup-shaped; filaments connate,
puberulous. Fruit large, tubercular, foveolate."
This may be supplemented by the following
notes Swingle was able to make from a specimen in the herbarium of the
Arnold Arboretum, identified by Tanaka as L. crassifolia (Tan. ident., No. A-328; coll. by H. S. Yates, No. 766, east coast of Sumatra).
This specimen has rather thick,
semicoriaceous leaves, with 12-15 pairs of lateral veins visible on both
surfaces, more conspicuous below, arising at an angle of 45°-55° with
the midrib; terminal leaflets 21-22.5 X 7.5-8 cm, lateral leaflets
16.5-18.5 X 6-6.5 cm; petiole 11-14.5 cm long. An
inflorescence shows 6 fruits with a persistent, cup-shaped calyx, 7-9 mm
wide, 2.5-3 mm high, with 5 (?) blunt, short lobes; pedicels 6-8 mm
long, articulated with the short lateral branches (3-5 mm long) of the
inflorescence; fruits (dried herb. spec.) fusiform, apex acute, with
apparently persistent style, base abruptly rounded.
This species differs from L. scandens in having blunter, thicker leaves, with evident venation, and in having pubescent filaments. L. crassifolia was evidently included in L. scandens in many of the older floras of the Malayan region.
3. Luvunga nitida Pierre, Flore Forest. Cochinch. 4: text to pl. 288B. 1893. Illus. Pierre, loc. cit. pl. 288B (1-8).
Type.—French Indo-China, Cambodia, Province of Tran (Pierre, No. 3876). Herb. Mus. Hist. Nat., Paris.
Distribution.—South Vietnam: Pell
Mountains in Chaudoc Province; Cambodia: Tran Province (the original
localities cited by Pierre; not known elsewhere).
Leaflets elliptic or oblong, abruptly
acuminate, obtuse or acute at the tip, usually obtuse at the base (11-20
X 5-8 cm), having about 10 pairs of widely spaced, faint nerves;
petioles 7-8 cm long; flowers 4-merous, peduncles 3-4 mm long; sepals 4,
fused together, ciliate on the margins; petals 4, oblong, rounded and
blunt-pointed at the tip, reflexed when fully open, stamens usually 6 or
7, filaments glabrous, slender, free except at the very base, where
they are connate, anthers oblong; ovary, with 3 or 4 locules, seated on a
disk 1 mm high, with 2 superimposed ovules in each locule; style rather
thick, 4.5-5 mm long, summit expanded into the truncate stigma; fruit
unknown.
This species was considered a synonym of L. scandens by Tanaka (1930a,
p. 52). However, the free stamens and the broad leaflets,
bluntly rounded at the base with only about ten pairs of faint veins, as
well as the style gradually expanded into the truncate stigma, show
that it is quite different. It is much more closely allied
to L. eleutherandra, from which it differs in having glabrous, filiform staminal filaments and larger leaflets with obtuse bases.
4. Luvunga eleutherandra Dalz. Hook. Kew Jour. Bot. 2:258. 1850. Illus. Engler, Die Nat. Pflanzenfam. 3(4):189, fig. 109,M-R (fls.). 1896; ibid. 19a:323, fig. 147,M-R. 1931; Talbot, Forest Fl. Bomb. Presid. 1:197, fig. 120 (lvs. and fts. [sic]). 1900.
Type.—British India, Bombay Presidency, Syhadree Mountains (Dalzell, No. 54). Herb. Kew.
Distribution.—India, Ceylon (also reported, probably erroneously, from Malay Peninsula, Sumatra, and Java).
Branches flexuose, with sharp, somewhat
deflexed, nearly straight spines, 1.5-2 cm long; leaflets 7.5-13 X
3.5-6.5 cm, elliptic-oblong or obovate, shortly acuminate, base usually
acute; petiole 2.5-7.5 cm long; flowers small, 4-merous; calyx
cup-shaped, almost entire or obscurely 4- or 5-lobed, truncate,
puberulous; petals 4, elliptic-oblong, reflexed, 6-7 mm long; stamens 8,
shorter than the petals, filaments free, dilated, finely pubescent;
style short, stout; fruits ellipsoid, small, 2.5-3.5 X 1.5-2 cm, peel
rough and pitted.
This small-leaved and small-flowered
species is found, according to C. E. C. Fischer (1921), in the western
part of peninsular India from Konkan southward to the Anaimalai Hills in
the Coimbatore district in evergreen forests above 3,000 ft. altitude
(between Lat. 10° 13' and 10° 32' N.).
5. Luvunga angustifolia (Oliv.) Tan. Bul. Soc. Bot. France 75:711. 1928. Luvunga eleutherandra Dalz. var. angustifolia Oliv. Jour. Linn. Soc. Bot. 5(2):44. 1861.
Type.—Ceylon (Walker and Thwaites, No. 1195).
Distribution.—Ceylon.
Branches with spines like those of L. eleutherandra
but slightly shorter (about 2.5 cm); leaves 3-foliolate with petioles
3.4-6.5 cm long; leaflets very variable, oval-lanceolate or
linear-lanceolate, shortly acuminate at the apex, entire, 7.5-20 cm
long; filaments free, subulate, glabrous (instead of finely pubescent as
in L. eleutherandra); fruits 2 cm diam.; globular (instead of ellipsoid as in L. eleutherandra).
This Ceylon species as described by Trimen, (1893, p. 224) and Tanaka (1928b, pp. 711-12) appears to be fairly distinct from L. eleutherandra. A careful comparison should be made of the plant of western peninsular India on which Dalzell based his L. eleutherandra in 1850 and of the Ceylon plant on which Oliver established his variety beta (angustifolia)
in 1861. Both the species of western peninsular India and
that of Ceylon were said by Talbot (1909, p. 197) to grow at altitudes
of from 3,000 to 5,000 feet in evergreen forests. L. eleutherandra occurs only about 200 miles northeast of the mountain region of south-central Ceylon where L. angustifolia is found. L. angustifolia is
said to show a tendency to dioecism. Thwaites stated (1864,
p. 48): "…this species would appear to be dioecious, as in some plants
the ovaries of all the flowers are entirely without ovules."
6. Luvunga sarmentosa (Blume) Kurz, Jour. Asiat. Soc. Bengal 39(2):69. 1870. Triphasia sarmentosa Blume, Bijdr. Fl. Nederl. Indie 152. 1825.
Type.—Java, Salak (Blume). Rijks Herb., Leiden.
Distribution.—Java; Sumatra; Borneo; Malaya; southern Burma: Tavoy in Tenasserim.
Leaves 3-foliolate, leaflets usually
small, about 12.5 cm long (but up to 30 cm long on young plants,
according to Koorders, 1912, p. 426), obscure venation, elliptical or
obovate (young leaflets sometimes linear, acuminate, as narrow as 30 X 3
cm), abruptly acuminate at the tip, sometimes short-caudate, but the
very tip bluntly rounded, acute or broadly rounded at the base; flowers
small, with free, very pubescent filaments; calyx 2-3 mm diam., with 5
triangular, minutely pubescent acutish lobes; fruits small.
In spite of Kurz's recognition of this plant in 1870 as a species of Luvunga distinct from L. eleutherandra, it was not considered by other taxonomists to be a distinct species until Tanaka (1931b, p. 9) published very helpful notes on the species of Luvunga
found in the Dutch East Indies (now West Irian, Indonesia).
He examined in the Leiden herbarium the type specimens of Blume on
which L. sarmentosa was founded and was able to distinguish it from L. eleutherandra of western peninsular India and from L. angustifolia of Ceylon.
7. Luvunga borneensis Hochr. Cat. Hort. Bogor. 1:41. 1904; and (simultaneously?) in Pl. Bogor. Exsic. 19. 1904.
Type.—Borneo, Sambus (Hochreutiner). Herb. Hort. Bot., Buitenzorg, Java (now Kebun Raya, Bogor, Java).
Distribution.—Known only from the original locality, but it is cultivated in the Botanic Garden in Bogor, Java.
[After Hochreutiner]: "Differs from L. eleutherandra [probably L. sarmentosa is
intended] having corolla and especially the calyx (5 mm high and 5 mm
wide) larger; flowers 5-merous [instead of 3-4-merous]; stigma capitate
and much larger; flower buds acorn-shaped; inflorescences
fewer-flowered. It differs from L. Motleyi in having
petioles 7.5-15.5 cm long; petioles 8-10 mm long; leaflets 9-16.5 cm
long and 5-7.5 cm wide; flowers in cymes no denser than in L. eleutherandra [L. sarmentosa?]."
Unfortunately, no additional information
has been published since 1904 and no additional collections of this
plant have been made in Borneo. Tanaka did not see the type
specimen in the herbarium of the Botanic Garden at Buitenzorg (now
Bogor), Java, nor did he report on Hochreutiner's authentic specimens of
this species distributed in his Plantae bogorienses exsiccatae,
No. 30, in 1904. It has been possible to examine (in
Washington, D.C.) an authentic flowering specimen of this species
distributed in the exsiccatae by Hochreutiner as well as a specimen from
another plant growing alongside in the same botanical
garden. They show the following characters: Spines on
sterile shoots about 2 to 2.5 cm long, very strongly recurved and very
sharp, but none on the flowering shoot; leaves trifoliolate; petioles
2.5 to 8.5 cm (usually 5 to 8 cm) long; leaflets broadly elliptical,
abruptly acuminate at the apex, acumen blunt on the authentic flowering
specimen and acute on the sterile plant, broadly cuneate or rounded (on
small leaves) at base, with 10 to 14 pairs of parallel veins scarcely
visible on the upper surface but very evident on the under surface in
dried specimens; inflorescences axillary, composed of 1 to 4 short (3 to
4 cm), divaricately branched cymes; pedicels 3 to 4 mm long; calyx
cup-shaped, very finely pubescent, 3.5 to 5 mm wide and 3 to 4 mm deep,
with five broadly rounded lobes, finely ciliate on the margins; corolla
and stamens lacking; pistils 7 to 9 mm long; ovary slender, finely
pubescent.
8. Luvunga motleyi Oliv. Jour. Linn. Soc. Bot. 5(2):44. 1861.
Type.—Borneo, Banjarmassing (Motley).
Distribution.—Borneo, Sumatra.
[After Oliver, 1861, p. 44]: Branches
slender, glabrous; petioles of the size of a crow's quill, 10-12 in.
[25.5-30.5 cm] long; petiolules sometimes 8-10 lin. [16-20 mm] long;
leaflets obovate-lanceolate, entire or slightly undulate-crenate, 9-18
in. [23-46 cm] long, 4-6 in. [10-15 cm] wide; flowers on short pedicels,
in dense, depressed, axillary cymes; calyx somewhat cupulate, with 5
small, triangular lobes or scarcely lobed; petals 5 (?); stamens 10,
free; ovary with 3 or 4 locules.
Tanaka (1931b, p. 9) noted that
this species has extremely large leaflets with distinct venation, large
flowers with shallow calyx, and free, very pubescent filaments.
9. Luvunga philippinensis Merr. Phil. Jour. Sci. Bot. 3:233. 1908.
Type.—Philippines, Mindanao, Zamboanga (Whitford and Hutchinson, No. 9104). Herb. Bur. Sci., Manila.
Distribution.—Philippines: Mindanao Island; Borneo.
[After Merrill]: A climbing vine;
petioles 9-13 cm long; petiolules stout (5 mm); leaflets 15-25 X 6-10
cm, subcoriaceous, oblong to oblong-elliptical, apex acuminate, the
acumen blunt or retruse, base acute, margins entire, with 8-10 pairs of
irregular nerves, somewhat prominent beneath, anastomosing,
"inflorescences of small, usually 3-flowered, racemose cymes, borne on
the branches below the leaves or in the leaf-axils"; pedicels 4-5 mm
long; flowers white, fragrant; calyx cup-shaped, about 4 mm wide,
truncate or very obscurely 5-toothed, its stipe 2 mm long; petals 3 or
4, oblong, obtuse at apex, 9-10 X 3.5-4.5 mm; stamens free, filaments
short, swollen, glabrous, about 6 mm long; ovary with 4 locules, oblong,
quadrangular in cross section, about 3 mm long, 1.2 mm thick, scarcely
narrowed into the stout style, nearly equaling the ovary in length;
stigma capitate.
Tanaka (1931b, p. 9) found that Luvunga philippinensis differs from his L. crassifolia in having indistinct venation, small flowers, free pubescent filaments, and large fruits borne on a small calyx.
The original description was based on
specimens with spineless twigs, such as are not uncommon in fruiting
branches. Undoubtedly rapidly growing young branches of this
species will be found to bear the retrorse (but not coiled) spines
characteristic of this genus.
Luvunga philippinensis is well distinguished from L. papuana (the
only species known to the south and east some 3,600 km distant in
northeastern New Guinea), which has smaller acuminate leaflets, longer
style, ovary with 2 to 4 locules, and much more strongly recurved
spines, sometimes making a complete circle or even more!
It also differs from the species which
occur from 800 to 1,600 km to the southwest, in Borneo; (1) from L. borneensis, in having 3- or 4-merous flowers, with smaller calyx, longer petioles, and larger leaflets; (2) from L. motleyi, in having shorter petioles, smaller leaflets, and smaller flowers with glabrous filaments; and (3) from L. crassifolia, in having inconspicuous, irregular lateral veins, smaller flowers, glabrous filaments, and leaflets acute at the base.
10. Luvunga papuana Lauterb. Bot Jahrb. 55:260. 1918. Illus. Lauterbach, loc. cit. 55:261, fig. 7,A,K; Engler, Die Nat. Pflanzenfam. 19a:324. 1931.
Type.—Northeastern New Guinea, Mai River, Sepik (Ledermann, No. 7392). Cotype: Pfingstberg, Sepik (Ledermann, No. 7505).
Distribution.—New Guinea.
[After Lauterbach's descriptions and
figures]: Branches terete, with axillary, very strongly reflexed,
slender, sharp spines coiled in a spiral manner (sometimes more than one
turn!); leaves 3-foliolate or rarely 1-foliolate; petioles short (about
10 mm on 1-foliolate leaves; 8-17 cm on 3-foliolate leaves); leaflets
10-18 X 6-9 cm, broadly lanceolate, obtusely-acuminate at the tip, acute
and decurrent at the base, subcoriaceous, shiny above, dull below,
margins entire, revolute, with about 9 pairs of inconspicuous lateral
nerves; inflorescences fascicled, many-flowered, axillary cymes, 2-4 cm
diam.; pedicels 5 mm long, calyx (in the flower bud) 1.3 mm diam.;
petals 3-4, 6 X 3 mm; stamens 8, 5 mm long, with glabrous filaments
1-1.5 mm long in the flower bud; ovaries ovoid, lageniform, glandular,
2-locular, with 8-10 vertical furrows (probably between rows of oil
glands); style thick, 4 mm long, merging gradually into the ovary;
stigma somewhat capitate ; fruits globose, about 12 mm diam., rind
thick, granular, white; seeds 1, 8 mm long, with a membranous testa.
This species, which is the
southeastern-most species of the genus and the only one found so far in
New Guinea, is strikingly different from the others in having slender,
sharp, very strongly recurved spines (shown by Lauterbach as arching
downward to touch the stems below). The ovary is shown as
having glands apparently arranged in eight or ten vertical lines marked
by slight ridges on the ovary. The fruits are the smallest
known in the genus, being only about 12 mm in diameter. Both
the description and the illustration show that some of the leaves are
unifoliolate and very short-petioled (as short as 1 cm).
This species seems clearly distinct from all others known in the genus.
A plant apparently belonging to this
species was collected for the 1936 Richard Archbold Expedition to New
Guinea by L. J. Brass (No. 7425, August, 1936) at Oroville camp, Fly
River, in Papua, southeastern New Guinea. A specimen in the
herbarium of the Arnold Arboretum has Brass’s notes on the label which
read: "fruits white, obovate, about 3-5 cm more or less long and 3 cm
diam." The strongly recurved spines and coriaceous leaves,
shiny-green above, make it very probable that this plant is L. papuana
in spite of its large fruits, and make it likely also that the small
fruits mentioned by Lauterbach in the original description were
immature.
IMPERFECTLY KNOWN SPECIES
11. Luvunga calophylla Kurz, Jour. Asiat. Soc. Bengal 39(2):69. 1870.
Type.—Bangka Island (near Sumatra)
at Jébús (Teijsmann, No. 3223). Herb. Hort. Bot.,
Buitenzorg, Java (now Kebun Raya, Bogor, Java).
Distribution.—Known only from the type locality.
[After Kurz]: Leaves 3-foliolate;
petioles 20-23 cm long; leaflets 25-30 X 4 cm, obovate-lanceolate, shiny
on both surfaces, lateral nerves conspicuous; flowers in short,
glabrous cymes; calyx large, 5-lobed, truncate, glabrous; petals,
styles, etc., lacking; fruits (immature) oblong or ovate-oblong, showing
the base of the style, "vesiculose-papillose." Kurz said of
it: "A very distinct species with leaves much resembling those of Zanthoxylum euneurum Miq. [= Evodia euneura Miq.]."
The absence of flowers has prevented the accurate placing of this species. Kurz knew Luvunga well and his opinion is of value. L. calophylla is carried in the Index Kewensis (Hooker and Jackson, 1895-1938) as a valid species.
12. Luvunga tavoyana Lindl. ex Oliv. Jour. Linn. Soc. Bot. 5(2):44. 1861.
Type.—Southern Burma, Tenasserim, Tavoy ("W. G[riffith]," Wall. Cat., p. 217, No. 6383).
Distribution.—Known only from the original collection.
[After Oliver, 1861, p. 44]: Leaves with
petioles 7.5-15 cm long; leaflets 10-20 cm long, oblong-elliptical;
flowers in short fascicles, or panicles, 1.2-5 cm long; stamens free or
slightly united at the base; ovary with 3 or 2 locules. "It
occurs both unarmed and with strong recurved axillary spines."
Oliver did not consider this to be a good species but rather a connecting link between L. scandens and L. eleutherandra that
might warrant their union under one species. Such a union
seems very improbable in the light of our present knowledge of Luvunga. L. tavoyana should be compared critically with L. calophylla and L. nitida. It cannot be placed with any certainty at present.
XIII. Paramignya Wight
XIII. Paramignya Wight, Ill. Ind. Bot. 1:108, 110, pl. 42. 1840. Atlantia Guill. (pro parte, non Corrêa), in Lecomte, Not. Syst. 1:176. 1910.
Type species.—Paramignya monophylla Wt.; native to British India, Ceylon, and southern Burma.
Distribution.—India; Ceylon;
Burma; southern China: Hainan Island; Laos; Cambodia; North Vietnam;
South Vietnam; Thailand; Malay Peninsula; Sumatra; Sumbawa; Borneo;
Philippines; northeastern Australia.
Common name.—Unifoliate liana-limes (or paramignya).
Woody vines clambering up trees and
shrubs by means of recurved spines; leaves 1-foliolate; petiole usually
showing a pulvinoid, more or less swollen segment articulated with the
leaf blade above, and the rigid portion of the petiole is also
articulated with the twig below; flowers white, fragrant, often large,
4-5-merous; stamens twice as many as the petals, usually with
elongate-linear anthers; disk an elongated columnar gynophore; ovary
with 3-5 locules, 1 or 2 ovules in each locule; fruits globose or
obovoid, often being narrowed toward the base, with a thick peel, seeds
rather flat.
As here used, Paramignya is a
genus containing about twelve very closely related species, often
difficult to distinguish from a study of herbarium material.
Two species native to Thailand, P. surasiana and P. rectispinosa, and one native to the island of Hainan in extreme southeastern China, P. confertifolia,
have very small ovaries, much shorter than the styles, but otherwise
they are very similar to the typical species of the genus.
Besides the twelve typical species of Paramignya there are three aberrant species that may possibly prove upon study of good material not to belong to the genus Paramignya. One of these species, P. lobata,
a native of the Malay Peninsula, has prominently 2- to 5-lobed fruits,
usually broader than long and bright red in color when ripe.
This species has very short retrorsely curved spines and is evidently a
woody climber. P. cuspidata, also native to the
Malay Peninsula, similarly has very short spines but apparently they are
not retrorse; it is not a high-climbing vine but rather a spiny
straggling shrub that probably clambers over low trees, shrubs, and
other vegetation. It sometimes has recurved spiny lateral
twigs on the branches that might aid in clambering over other
plants. The third aberrant species is P. trimera, which has a wide range from northeastern Australia and Timor Island to the islands of the southern Philippines and Indonesia.
The fruits of the typical species of Paramignya
have small or medium-sized (0.1 to 0.6 mm) oil glands in the peel, and
larger, sometimes much larger, ones (0.8 to 2 mm) below the peel in the
mesocarp or even sometimes in the endocarp, not far from the locule
cavity. In P. longipedunculata there are very
commonly two layers of oil glands, one composed of very small (0.1 to
0.5 mm) glands in the peel and another (sometimes two layers deep)
composed of much larger (0.5 to 1.5 or 2 mm) globular or ellipsoid
glands in the mesocarp with the longer diameter tangential.
In this species, the two kinds of oil glands (the larger ones perhaps
mucilage glands) are separated by a layer containing numerous small
vascular bundles.
The typical species of Paramignya are undoubtedly closely related to Luvunga.
Both of these genera include woody vines clambering high into trees and
holding fast by means of recurved spines, and both genera have fruits
with dimorphic oil glands. Luvunga has trifoliolate leaves with very long petioles, whereas Paramignya has
unifoliolate short-petioled leaves. There are other minor
differences such as the straight twigs (with few internodes) of Luvunga and the more or less zigzag twigs of Paramignya; also the presence of a well-defined pulvinus, at the base of the leaf in Paramignya, which twists so as to place the leaf in the proper position to catch incident light.
Sometimes Luvunga produces
unifoliolate leaves and then the petioles are very much shorter, not
very different in length from those of some of the larger-leaved species
of Paramignya, for example, P. andamanica. Probably these two genera were derived from some common ancestor. The aberrant species P. lobata and P. cuspidata may, however, be related to Pamburus.
The species of Paramignya are
difficult to distinguish unless cognizance is taken of all available
characters. Unfortunately, many of the published
descriptions merely distinguish between the few species growing in a
single region; this does not permit accurate comparison of species
growing in distant regions. For the present it is easiest to
key out separately the species of the four principal regions where this genus is native.
1. Paramignya monophylla Wight, Ill. Ind. Bot. 1:108, pl. 42. 1840. Atalantia correae Guill. 1910. Illus. Wight, loc. cit. pl. 42; Engler, Die Nat. Pflanzenfam. 3(4):191, fig. 111,A-B. 1896; ibid. 19a:327, fig. 150,A-B. 1931; Talbot, Forest Fl. Bomb. Presid. 1:200, fig. 122. 1909; Guillaumin, in Lecomte, Not. Syst. 1:176, fig. 8(1). 1910; Swingle, in Bailey, Stand. Cycl. Hort. 5:2473, fig. 2763. 1916.
Type.—British India, Courtallum (Wight, No. 115). Herb. Univ. Glasgow (fide Tanaka, 1930b, p. 235).
Distribution.—India: western peninsula from Konkan northeast to Sikkim, Bhutan, Khasiak; Burma: Tenasserim; Ceylon.
Common name.—Indian paramignya.
Leaves oblong or elliptic, rarely
obovate, 6-12.5 X 2-4 cm, apices abruptly acute, sometimes acuminate,
base rounded; petioles 12-20 mm long; flowers solitary or in
few-flowered axillary clusters, large (25 mm diam.), 5-merous, fragrant;
calyx cupular, with 4-5 broad, obtuse lobes; petals 4-5,
lanceolate-oblong; stamens 8 or 10, free, filaments slender, compressed
below, subulate above, glabrous or pubescent; pedicels slender, 6-10 mm
long; ovary slightly furrowed, pubescent or glabrous, with 3-5 locules,
usually with 2 ovules (sometimes 1) in each locule; style pubescent
below, glabrous above; fruit ovoid or obovoid, pubescent or almost
glabrous, slightly angled and sometimes compressed, 2.5-3.5 X 2.5-3.3
cm, yellow, odorous, sometimes only 1-seeded; seeds compressed.
This species, the type of the genus, has
never been adequately studied or illustrated. The petioles
are not clearly articulated between the leaf blade and the twig, but the
upper portion is pulvinoid. The fruit was said by Wight in
the original description to be "pomaceous! endocarp 5-angled, between
coriaceous and fleshy, surrounded by cellular pulp and rind, one-
(always?) celled by the rupture and absorption of the
partitions." He also stated that the fruit is "obtusely
5-angled and furrowed between, clothed with short matted
pubescence." Oliver (1861, p. 42) described the ovary as
"often slightly furrowed."
2. Paramignya scandens (Griff.) Craib, Fl. Siam. Enum. 1:235. 1926. Citrus scandens Griff. Not. Ad. Pl. As. 4:495. 1854; Paramignya citrifolia Oliv. Jour. Linn. Soc. Bot. 5(2):42 (excl. synonymy! [non Limonia citrifolia Roxb.]). 1861; P. griffithii Hook. f. Fl. Brit. Ind. 1:510. 1875; Atalantia griffithii Guill. in Lecomte, Not. Syst. 1:183. 1910. Illus. Griffith, loc. cit. pl. 587, fig. 1.
Type.—Northern Burma, "Serpentine Mines," Mogung (?) Valley (Griffith, No. 519).
Distribution.—Northeastern India: Assam State; northern Burma; Thailand.
The original description by Griffith
reads, translated, about as follows: "A spiny climbing shrub; spines
smaller on twiglets or on inflorescences; twigs, petioles, and leaves
pubescent; flowers white like the stamens, fragrant (with a suave odor),
petals tinted green outside above the middle. Habitat: In wooded hills near the Serpentine Mines, toward Burma.
"A very distinct species, rare in upper
Assam; common in the valley of the Mogoung, especially four leagues
toward Serpentine Mines."
Griffith (l.c., vol. 4, pl. 587) shows a
flowering twig, 24 cm long and 4.5-5 mm diam., with 10 leaves, and a
portion of a large twig, 10-11 mm diam., with a single leaf and a flower
borne on a lateral twig, 4-5 mm diam.; also a single fruit.
No spines are shown on either twig.
The plate shows the following characters:
Leaves lanceolate, with acute or slightly acuminate (one leaf is
obtuse) apices, gradually narrowed, then abruptly rounded at the base;
leaf blades 9-13 X 3.5-5.5 cm, glabrous above (?) but with scattered
hairs below, veins 6-7 pairs, visible on both surfaces; petioles 9-15 mm
long, 2.2-3 mm diam., pubescent; flowers arising singly or 2 (or 3?) in
the axils of the leaves, 18-23 mm long, pedicels 6-8 mm long, 2 mm
wide, with small bractlets near the base, pubescent like the petioles;
calyx 4.5-6 mm wide, 4-4.5 mm long, with acute lobes 1.5-2.5 mm long;
petals strap-shaped, narrowed toward the rounded tips, 18-20 X 3-4 mm,
glabrous; staminal filaments 13-15 mm long, slender, glabrous, anthers
short, 3 X 1.5 mm (less than 1/4 the length of the filaments), long
oval; pistil 18-21 mm long; ovary subglobose, 4.5 mm diam., glabrous;
style glabrous, 14-17 X 1-1.1 mm, stigma capitate, 3-3.8 mm diam.;
fruits ovoid, 25-30 mm, bluntly pointed at apex, rounded at base, finely
pubescent (?), borne on a subglobose (?) gynophore (4.5 mm diam. below)
which remains attached to the apparently glabrous persistent calyx, no
larger than when the flower opened. The plate gives every
evidence of having been made carefully and accurately from a good
flowering specimen.
Hooker (1875, vol. 1, p. 510) described P. griffithii (evidently named in honor of Griffith) and included Griffith's Citrus scandens,which
he stated has very small flowers (only 6 to 8 mm long); yet Griffith's
plate shows flowers 15 to 18 mm long. Hooker stated:
"Griffith's figure is a great exaggeration, as his specimens show," but
so great an exaggeration as this seems improbable, especially since the
plate looks like a good cut made from the living plant.
Possibly the best material was used to make the plate and the dried
specimens that were put in the herbarium do not show the flowers
properly and may even belong to another species.
Griffith described his plant as a species of Citrus, and because it was so utterly different from any known Citrus a detailed description probably seemed unnecessary. It would not be surprising if Griffith mixed up two species of Paramignya in his material of Citrus scandens.
It seems best for the present to let P. scandens stand
as described and figured by Griffith and avoid attempting to include in
it the widely different forms that have since been assigned to
it. New material from the type locality, Mogoung Valley (?)
in northern Burma, is needed to settle the status of this species.
2a. Paramignya scandens subsp. ridleyi (Burkill) Swing. Jour. Wash. Acad. Sci. 28:533. 1938. Paramignya ridleyi Burkill, Gard. Bul. Straits Settl. 5:214. 1931; P. citrifolia var. beta (pubescens) Oliv. Jour. Linn. Soc. 5(Suppl. 2):42. 1861; P. griffithii Hook. f. 1875, in part (only as regards the Malacca specimen, fide Ridley); P. griffithii Ridley (non Hook f.), Fl. Malay Penin. 1:356. 1922.
Type.—Singapore (Hullett).
Distribution.—Malay Peninsula: Malacca and Singapore.
Ridley described the Malay Peninsula plant under the name P. griffithii,
as follows: "Shrubs shortly spiny, glabrous or pubescent.
Leaves coriaceous, elliptic or oblong, short, blunt-acuminate, 3 to 5
in. [7.5-12.5 cm] long, 1.5 to 2.3 in. [3.8-5.8 cm] wide, base
rounded. Flowers solitary or fascicled, axillary, slender,
0.3 in. [6 mm] long, white, fragrant. Calyx acutely
5-lobed. Petals oblong, 0.3 in. [7.5 mm] long,
blunt. Stamens 10, filaments hairy, longer than the
linear-oblong anthers. Ovary 5-celled; ovules 2 in each
cell."
Burkill (1931, p. 214), in making a new species for this plant, wrote: "P. Griffithii
Hook. fil in loc. cit., [Hooker f., 1875, vol. 1, p. 510] only as
regards the Malacca specimen: Ridley, Fl. Mal. Penin., 1, 1922, p.
356. This species has much longer pedicels than P. scandens and
is abundantly distinct. It was collected in Malacca by
Griffith, and by Hullett in Singapore. The backs of the
leaves are less hairy than those of P. scandens."
Unfortunately, in the absence of type
material, no additional details can be given for this
subspecies. It must therefore, for the present at least, be
kept distinct not only from P. scandens, but from P. monophylla (= Atalantia correae Guill.), all of which were considered by Tanaka (1930a, p. 162) to be P. scandens.
Even as matters stand, the subspecies is
fairly well delimited by its broad elliptic-oblong leaves (7.5 to 13 by
3.8 to 6 cm) and its very small flowers borne singly or in few-flowered
axillary fascicles, with acute calyx lobes and blunt-oblong petals 6 to
7.5 mm long, and hairy filaments longer than the anthers.
It differs from P. scandens subsp. hispida in being glabrous or less pubescent with respect to leaves, calyx, and gynophore; from P. andamanica in having much smaller leaves, smaller flowers with larger calyx (?) and shorter pedicels; from the little-known P. citrifolia in having longer pedicels and filaments longer than the anthers; from P. armata in having much larger leaves, with longer petioles and stouter pedicels. It differs from P. surasiana and P. rectispinosa by having styles only three times as long as the ovary.
2b. Paramignya scandens subsp. hispida (Pierre) Swing. Jour. Wash. Acad. Sci. 28:533. 1938. Atalantia hispida Pierre ex Guill. in Lecomte, Not. Syst. 1:182. 1910.
Type.—French Indo-China, Cambodia, Bienhoa Province.
Distribution.—Known only from the type locality.
Differs from the species in having longer
petioles and smaller flowers with shorter, broader petals.
It resembles more closely the subspecies ridleyi but has somewhat
smaller leaves and anthers apparently shorter in proportion to the
length of the filaments, and possibly longer recurved spines.
Guillaumin (1911, p. 674) described Atalantia hispida Pierre
about as follows: Branches slender, at first very pubescent, later on
becoming glabrous, with spines about 10 mm long; leaves oval or
oval-oblong, 6-10 X 2-4 cm, with a short acuminate tip, rounded or
subcordate at the base, velvety-pubescent below, veins invisible on
upper surface, parallel and close together below; petiole
velvety-pubescent, up to more than 2 cm in length; inflorescences
solitary, axillary; flowers 10 mm long, on velvety pubescent pedicels 5
mm long, with small bracts at the base; calyx cup-shaped, 2-3 mm long,
sepals 5, oblong, acute (valvate in flower bud), pubescent without,
glabrous within; petals 5, elliptical, 1 cm long, glandular, slightly
pubescent without; stamens 10, 2/3 length of petals, filaments dilated,
pubescent, usually free (often 2 or 3 connate), anthers elliptical, half
as long as the filaments, not apiculate; gynophore cylindric,
pubescent, glandular, crenulate above; ovary ovoid-globular, 5-angled,
glabrous, shorter than the style, with 5 locules, each containing 2
ovules, style cylindrical, glabrous, stigma capitate, slightly 5-lobed;
fruits small (according to Pierre).
Tanaka (1928b, p. 712) considered this subspecies to be a synonym of P. scandens (Griff.)
Craib, but it appears to have smaller flowers with decidedly shorter
and broader petals. It will not be possible to understand
clearly these three forms here referred to P. scandens until studies can be made on collections of all three in comparable states.
3. Paramignya armata (Thwaites) Oliv. Jour. Linn. Soc. Bot. 5(2):43. 1861. Arthromischus armatus Thwaites, Enum. Pl. Zeyl. 47. 1858.
Type.—Ceylon (Thwaites, No. 1187). Herb. Kew.
Distribution.—Ceylon (hotter parts of the island).
Leaves oval, elliptic or
elliptic-lanceolate, obtusely caudate-acuminate, rounded at the base,
5-8 X 2-3.5 cm; petioles short (8-11 mm); pulvinus 3 mm long,
articulated with the petiole and with the leaf blade; flowers small (6
mm long), solitary or in few-flowered axillary clusters, 4-5-merous;
pedicels very slender (0.4-0.5 mm diam.), 6-8 mm long; calyx minute,
obtusely 4-5-lobed, lobes acute; petals oblong, very much imbricated;
filaments linear-subulate, pubescent, slightly dilated in the middle;
ovary pubescent, borne on a gynophore equaling it in height, with 3-4
locules, ovules usually 1 in each locule; style long, glabrous,
cylindric, stigma globose; fruit subglobose, apiculate, 10-20 mm diam.,
yellow, 1-4 seeded.
This species is said to have pulpy fruits but nothing is known about the nature of this pulp.
Thwaites directed attention to its
"jointed leaf stalk," a very striking character often overlooked by
subsequent authors. The petiole shows a stiff straight
petiole proper, at the tip of which is articulated a short fleshy
pulvinus.
4. Paramignya beddomei Tan. Jour. Bot. Brit. & For. 68:230. 1930. Paramignya armata Beddome (non Oliver), Icon. Pl. Ind. Or. 65, pl. 275 (excl. descript.). 1874. Illus. Beddome, loc. cit. pl. 275 (as P. armata).
Type.—British India, Madras, Anamaly (Anaimalai Hills) (Beddome, No. 1052). Herb. Brit. Mus., London.
Distribution.—South peninsular India and Ceylon (fide Tanaka).
Twigs very slender, conspicuously zigzag,
pubescent with fine appressed hairs; leaves medium-sized, blade 70-75 X
35-40 mm, ovate, caudate, broadly rounded at base, pubescent on the
midrib, especially below, petiole long (10-15 mm), sigmoid with an
articulated pulvinus occupying the upper third, pubescent; flower buds
large (10-12 X 3-4 mm), cylindric; flowers solitary, axillary, large
(25-30 mm diam. when open) pedicels 8-12 mm long; calyx cupulate, lobes
short, obtuse, auriculate; petals linear, bluntly rounded, 15 X 4-5 mm;
filaments apiculate, very pubescent for their whole length, anthers
linear, but contorted at maturity; ovary 4-5-lobed, cylindric, almost
glabrous, but sparingly pubescent in upper portion, about as long as the
disk, ovules 1 in each locule; style linear, very glandular, stigma
depressed-globose, 5-lobed; fruit globose, not apiculate.
Beddome's figure (l.c., pl. 275) shows
short recurved single spines, 6 to 12 mm long, tapering to a fine
point. This species has been confused by previous students
of Paramignya with P. armata, from which Tanaka separates it by many characters.
5. Paramignya citrifolia (Roxb.) Oliv. Jour. Linn. Soc. Bot. 5(2):42 (exel. descript.; valid for name only). 1861. Limonia citrifolia Roxb. Fl. Ind. 2:379. 1832; Paramignya citrifolia Hook. f. Fl. Brit. Ind. 1:510 (excl. synon.; valid for descript. only). 1875; Atalantia citrifolia (Roxb.) Kurz, Jour. Asiat. Soc. Bengal 39(2):69. 1870.
Type.—Northeastern British India near Burmese boundary, Chittagong (Roxburgh, No. 340). Herb. Brit. Mus., London.
Distribution.—Reported from Bengal and northeastern India (now partly East Pakistan) by Tanaka (1930b, p. 61).
Roxburgh's original description (under the genus Limonia) reads: "Shrubby; armed with recurved spines. Leaves simple, elliptically oval, entire, obtusely acuminate. Flowers axillary. Berries ovate, few-seeded.
"A very ramous, rigid, well-armed shrub,
of five or six feet in height, a native of the forests of Chittagong,
and with the other armed species, well adapted for fences.
Flowering time the hot season.
"Young shoots polished. Thorns axillary, solitary, short, somewhat recurved. Leaves
alternate, round-petioled, elliptic, with an obtuse, somewhat
lengthened point, entire, smooth, but marked with numerous pellucid
points, as in many Aurantiae; from four to five inches long, and from two to three broad. Stipules none. Flowers small, white, short-peduncled, axillary. Bracts minute, about the insertion of the peduncles, and on them. Calyx five-toothed, having its substance marked with pellucid points. Petals five, oblong, smooth. Filaments ten, distinct, short, inserted round the base of the germ. Anthers linear, erect. Germ [ovary] ovate-oblong, five-grooved, on the outside five-celled, each cell containing two ovula attached to the axis. Style thick and short. Stigma sub-peltate. Berry ovate, of the colour and appearance of a lime, even to the little green cells in the cortex. Seeds from
one to four, separated by some few small fibers only, which are
scarcely to be traced when dry, oblong, having the sides agreeing in
shape with the number in the berry. Integument single, membranaceous. Perisperm none. Embryo inverse. Cotyledons conform to the seed. Radicle superior."
The type specimen in the British Museum (Roxburgh, No. 340; see Tanaka, 1930b)
of two fruiting twigs from Korelea Hill, collected in 1811 (?), shows
twigs, slender ultimate growth, 2-3 mm diam.; leaves 6-12 X 3-6 cm,
elliptical, abruptly acuminate but blunt at tip, base gradually rounded,
seldom very broadly cuneate, 12-14 pairs of lateral veins,
inconspicuous above but visible on under side, arising at a wide angle
(65°-70°) with the midrib; petioles 8-10 mm long, not clearly jointed to
the pulvinus; fruit subglobose, 12 X 14 mm, pedicel 6-8 X 1.5 mm, on
which the calyx, 5 mm wide but only 2-3 mm long, persists.
These notes are based on a photograph by Tanaka (No. 3789).
Hooker, who compiled his description
(without seeing any specimens) from Roxburgh's description and figure
(Mus. [E.I.C.] 2243, fide Oliver, 1861), found the following characters: "…Young shoots polished. Leaflet 4-5 by 2-3 in., quite entire. Flowers white, about 1/3 in. diam. Petals oblong. Filaments quite free. Ovary ovoid-oblong, 5-grooved; style short, thick; stigma subpeltate. Berry ovoid, pointed, of the colour and appearance of a lime, even to the little green cells in the cortex. Seeds 1-4,
separated by a few small dry fibers only, which are scarcely to be
traced when dry, oblong; testa membranous.—This plant is unknown to me;
the description is taken from Roxburgh's Flora Indica and drawings. Prof. Oliver referred to it in the preceding species [P. griffithii],
which differs in the form of the stamens, and (if Roxburgh's figure of
the ovary is correct) in wanting a style, but the said figures resemble
what an ovary would be were the style fallen away. I refer
it to Paramignya from the long anther and pointed fruit. Kurz has pointed out that Oliver's P. citrifolia and Griffith's Citrus scandens cannot be the same as Roxburgh's Limonia citrifolia (Jour. Asiat. Soc. Bengal, 1870, Pt. 2, 69)."
This very imperfectly known species has
been found with certainty only near Chittagong not far from the frontier
between East Pakistan and northwestern Burma. It is placed
by Hooker in the group of species having "flowers about 1/2 inch [12-13
mm] long. Calyx small with acute teeth," in which group he
also places P. griffithii and P. armata.
It would be very desirable to secure more
good herbarium specimens from the type locality,
Chittagong. Until this is done, it will be very difficult,
if not impossible, to determine with any certitude the affinities of P. citrifolia.
6. Paramignya grandiflora Oliv. Jour. Linn. Soc. Bot. 5(2):42. 1861.
Type.—Southern Burma, Tenasserim (?) (Lobb, No. 925). Herb. Kew.
Distribution.—Southern Burma: Tenasserim; Andaman Islands; Malay Peninsula (?).
Much like P. monophylla, having
equally large, solitary flowers, 18-19 mm long, but broader leaves,
broadly rounded at the base, pubescent below; petiole articulated with
the pulvinus (?); calyx cupular, lobes well developed, often cuneate at
tips and overlapping (imbricate?) at the base, ciliate; fruits unknown.
This species is native in southern Burma and the Malay Peninsula and is much like P. monophylla, having large flowers with five petals; the styles pubescent below and the stamens pubescent and similar in shape to those of P. monophylla.
The type collection was credited to Singapore by Oliver (1861, p. 42)
and is so labeled, but, according to Ridley (1922, p. 355),
erroneously. He suggested that it is from Tenasserim and
stated: "it is otherwise known only from Tenasserim" (where it was
collected by Wallich, No. 6361).
7. Paramignya andamanica (King) Tan. Bul. Soc. Bot. France 75:712. 1928. Paramignya armata var. andamanica King, Jour. Asiat. Soc. Bengal 62(2):223. 1894.
Type.—Andaman Islands (King). Herb. Kew.
Distribution.—Andaman Islands, North Vietnam, South Vietnam, Sumatra, Sumbawa, Sabah (North Borneo.)
King's original description and his type
specimen in the herbarium at Kew give the following characters: Twigs
slender, puberulous when young, soon becoming glabrous; spines single,
short, curved, pubescent; leaves large, elliptical or elliptic-oblong,
narrowed at apex into a blunt point, broadly rounded at base, 10-23 X
3.5-9 cm, with 10-12 pairs of veins making an angle of 65°-75° with the
midrib; petiole 12-25 mm, pubescent on the upper surface when young, not
distinctly articulated with the pulvinus; flowers 5-merous, paired or
solitary, axillary; flower buds slender, 14-18 mm long; pedicels long,
slender (18-20 mm), arising separately; calyx glabrous, short (3-4 mm),
deeply divided into 5 broadly obtuse lobes; petals about 4-5 times as
long as the calyx (15-16 mm), linear-oblong, obtuse; stamens free,
almost as long as the petals, filaments rather thick and woolly for the
lower three-fourths but filiform and glabrous above; ovary glabrous,
ovoid, seated on a short cylindric disk not broader than the ovary;
style elongate, slender, glabrous; fruits globular or turbinate,
glabrous, 12-16 mm diam.
Parkinson (1923, p. 108) reported it as
"fairly frequent" in several of the Andaman Islands. His
specimens were more vigorous than those seen by King, as he described it
as having curved spines about 5 cm long, leaves 10-23 X 4-9 cm, with
petioles 25 mm long (all of these measurements are the largest yet
reported for any species of Paramignya); flowers small (12-13 mm
long), on slender pedicels 25-38 mm long; filaments pubescent; fruits
12-13 mm diam., globular or obscurely 2-lobed. He found the
leaves "almost scentless when bruised."
Guillaumin (1911, p. 675) reported this species, under the name P. aramata,
as occurring in Cochin China (South Vietnam). He described
it as having curved spines only 6-12 mm long; leaves 7.5-12 X 3.5-4.5
cm; flowers on slender pedicels 30 mm long; calyx short (3 mm), lobes 5,
indistinct, rounded, ciliate; petals 3 times as long as the calyx;
stamens almost as long as the petals, dilated and pubescent at the base,
slender and glabrous at the tips; ovary globose, glabrous, 5-sided,
with a style 3 times as long; stigma capitate, flattened above,
attaining height of the stamens; fruit yellow, globose, borne on a
pedicel 30-35 mm long, showing the remains of the eccentrically placed
style.
This remarkable but little-known plant
reaches its best development in the Andaman Islands, although it grows
also in South Vietnam, and, according to Tanaka (1931b, p. 10),
in Sumatra, Borneo, and Sumbawa, which lie about 1,000 to 3,000
kilometers to the southeast. The Andamans are situated about
1,300 kilometers nearly west from South Vietnam.
It is curious that this species has not
been reported from southern Burma, southern Thailand, and the Malay
Peninsula. Possibly some of the small-flowered forms of Paramignya reported from the Malay Peninsula belong to this species as varieties or subspecies rather than to P. scandens or P. citrifolia.
This species, like Atalantia macrophylla (which also is native to the Andaman Islands), is remarkable for its extraordinary vigor, especially in its native habitat.
It is the only species of Paramignya that approaches the dimensions of some of the species of Luvunga (the other genus of woody vines belonging to the orange subfamily) in the length of its leaves and spines.
This species is related to P. armata,
of Ceylon, in having very similar small flowers, but differs in having
much larger leaves and spines, and, as King stated, in having fewer
flowers in the leaf axils.
8. Paramignya longipedunculata Merr. Phil. Gov. Lab. Bur. Bul. 35:24. 1905. Atalantia longipedunculata (Merr.) Guill. in Lecomte, Not. Syst. 1:221. 1910.
Type.—Philippines, Luzon Island, Rizal Province, Bosoboso (Ahern's collector). Herb. Bur. Sci., Manila.
Distribution.—Philippines: Luzon and Mindoro islands.
Common name.—Luzon paramignya.
Branches hairy, with spines 5-15 mm long,
retrorse and slightly curved, densely pubescent when young, but the
brownish, hardened tips glabrescent with age; terminal twigs dark green
when dry, densely pubescent; leaves oval or elliptic-ovate, 7-10 X 5-7
cm, with the apex abruptly acute or broadly short-acuminate, base
rounded, pubescent on lower surface, midrib densely pubescent below;
petioles 8-10 mm long, densely pubescent, pulvinus not visibly
articulated with the leaf blade or petiole; flowers solitary or in 2- or
3-flowered axillary clusters; pedicels densely pubescent, 1.5-3 cm
long, subtended by slender pubescent bracts, 1.1-2 mm long, borne at the
tips of short branches, 2.5-7 mm long; calyx cupular, densely
pubescent, 7 mm diam., 5-lobed, lobes erect, broad, ovate, 2.5 mm long;
petals 5, linear-oblong, 20 X 5 mm, densely pubescent without: stamens
10, filaments pubescent, 12 mm long, anthers 5 mm long; ovary with 5
locules; style about 15 mm long, densely pubescent; fruits broadly
ellipsoid, bluntly pointed at apex, conoid at base, 2.5-3 mm X 1.5-1.8
cm, subtended by the persistent calyx.
This is a large-flowered species like P. monophylla,
but differs in being more or less densely pubescent in all
parts. It also has much longer pedicels than that
species. Merrill (1923, p. 339) reported that it grows "in
forested ravines and in secondary forests at low and medium altitudes."
9. Paramignya mindanaensis Merr. Phil. Jour. Sci. Bot. 3:140. 1908.
Type.—Philippines, Mindanao Island, Lake Lanao, Camp Keithley (Mary Strong Clemens). Herb. Bur. Sci., Manila.
Distribution.—Philippines: Mindanao Island; also Samar and Luzon islands (fide Tanaka).
Branches glabrous except the flowering
twigs; leaves oblong-elliptical, glabrous, 9-12 X 3-6 cm, apex
acuminate, base rounded, veins indistinct; petioles 1 cm long; flowers, 1
or 2, axillary, about 17 mm long; pedicels slender, 10-15 mm long;
calyx cupular, slightly hairy, about 5 mm diam., 5-lobed, the lobes 1.5
mm long, rounded; petals imbricate, oblong, 12 X 5 mm, glabrous; stamens
10, filaments thickened, somewhat pubescent, about 7 mm long, anthers 4
mm long; gynophore about 2 mm long and 2 mm diam., crenulate; pistil 10
mm long, somewhat pubescent; ovary 5-angled, with 5 locules; style
stout; fruits (immature) 1.5-2 cm diam., usually curved, glabrous.
This species differs from P. longipedunculata
of Luzon Island in being, on the whole, less pubescent, since some
parts are glabrous, and in having larger leaves and smaller
flowers. It has been referred to P. grandiflora as a synonym by Tanaka (1932e, p. 425), who stated that the type specimen of P. mindanaensis is a typical P. grandiflora.
However, one of Lobb's specimens of the latter species from Singapore,
cited by Oliver in the original description, shows pedicels measuring 20
to 26 mm long, instead of 10 to 15 mm, as in Merrill's description of P. mindanaensis, and calyxes nearly twice as large as in the Mindanao species. Inasmuch as P. mindanaensis occurs
1,500 miles east of Singapore, it would seem best to maintain it as a
good species for the present. Tanaka found that specimens
from Luzon and Samar islands are much less pubescent than the type
material from Mindanao Island.
10. Paramignya surasiana Craib, Kew Bul. Misc. Inform. 1916:261. 1916. Paramignya griffithii Hook. f. Fl. Brit. Ind. 1:510 (pro parte) (so far as concerns the specimen from Pegu collected by McClelland, fide Craib). 1875.
Type.—Thailand, Chiangmai, Doi Sutep (Kerr, No. 2542).
Distribution.—Thailand; northern Burma: Pegu.
[After Craib]: Twigs puberulous; spines
recurved, 7-9 mm long; leaves obovate or elliptic-obovate, apex obtusely
caudate-acuminate, base broadly cuneate or rounded, 10-14 cm long
(including the acumen, which may be up to 1 cm long), 5.2-7.5 cm wide,
chartaceous, glabrous except for the shortly pubescent midrib, oil
glands abundant, conspicuous on the lower surface, lateral veins
straight, at least 10 on each side, prominent on the underside; petiole
1.5-1.7 cm long, puberulous; pedicels about 4 mm long with a few
bractlets below; flower buds oblong, rounded at the apex, up to 1.4 cm
long; calyx 5.5 mm long on the outside, curly pubescent without (like
the pedicels), appressed pubescent within, lobes unequal in length,
1-2.5 mm long, with rounded ciliate tips; petals white, at least 1.7 cm
long, glabrous; filaments 12 mm long, angular, flattened at the middle,
nearly glabrous at base, elsewhere white pubescent; ovaries short,
densely pubescent; style about 9 mm long, pubescent.
This species is still inadequately
known. The fruits, said by Craib to have been collected by
McClelland at Pegu in Burma, are not described by either J. D. Hooker or
Craib. The petals are very imperfectly known, and no
measurements of the ovary are available. However, since
Craib described this species along with P. rectispinosa, which has an exceptionally short ovary, and furthermore described the ovary of P. surasiana as "short," it is clear that this species also has a very short ovary. Even if the ovary of P. surasiana were twice as long as that of P. rectispinosa,
it would still be less than one-fourth as long as the
style. More and better material of this species is much
needed in order to place it accurately. It was collected by
Kerr in evergreen jungle in the same locality in which he discovered P. rectispinosa but at an altitude nearly 1,000 m higher, i.e., at 1,650 m instead of 660 m.
11. Paramignya confertifolia Swing. Jour. Arnold Arbor. 21:17. 1940. Illus. Swing. loc. cit. pl. 4, figs. 1, 2; fig. 3-17 this work.
Type.—China, Hainan, San Tsuen Mountain (Tsang Wai Tak, No. 15523). Herb. Univ. Calif., Berkeley.
Distribution.—Southeastern China: Hainan Island and Kwangtung Province.
A shrub, 3-5 m high, clambering over
shrubs; young twigs slender, terete, pubescent, with internodes 2-5 cm
long on vigorous shoots but much shorter, often only 8-10 mm long, on
fruiting branches; spines short (3-10 mm; usually 3-6 mm), recurved,
often reduced in size or wanting on the end branches, especially on
fruiting branches; leaves oval or oblong to long elliptical, usually
broadly rounded at the base (sometimes cuneate on longer leaves), the
very tip of the acumen bluntly rounded, midrib and lateral veins visible
on both surfaces but more distinct below, the 8-12 or more pairs of
lateral veins arising at an angle of 60°-70° with the midrib, the space
between being filled with smaller more or less parallel veinlets making
elongate reticulations, margins entire or irregularly and shallowly
crenulate; petioles 4-12 X 1-1.5 mm, flattened above, more or less
pubescent, wrinkled in dried specimens, pulvinoid portion not
articulated, the whole petiole curving more or less to place the leaf
blades in best position to catch the incident light; flowers axillary,
arising singly or in small clusters, sometimes in greatly reduced
racemes; flower buds cylindrical, 8-10 X 2.5-3.5 mm; pedicels slender,
4-5 mm long, 0.5-0.7 mm wide, glabrous, subtended by minute sparsely
hirsute bracts where the pedicels join the peduncles, which are hirsute;
calyx small, 2 mm wide, 1-5 mm high, brownish buff-colored (as is the
pedicel), lobes 5, triangular, with ciliate tips; petals 5, glabrous,
white when fresh, yellowish-brown when dry, 7-9 or 10 X 3-4 mm; stamens
10, filaments flattened, 5-6 mm long, anthers linear, 1.8-2 mm long;
disk cylindrical, not broader than the ovary base; ovary ovoid, 1.2-1.3 X
1 mm, strongly hirsute with yellowish-buff hairs, with 2 locules, each
with 2 ovules, narrowed abruptly into the sparsely hirsute style, 4.5-6 X
0.3-0.4 mm wide at base and more slender above, dehiscent shortly after
flowers open, stigma depressed globose, 0.5 mm high and 1-1.5 mm wide;
fruits at first sub-globose, glabrous, but when full-sized becoming very
rough, sometimes almost lobed with irregularly rugose folds of the
peel, which shows numerous sunken oil glands having a turpentine-like
odor and flavor, yellow when ripe, subglobose, 1.5-2 cm diam.,
apparently corky in places; seeds small, ovoid, monoembryonic.
This species has been identified as P. scandens (Griff.) Craib, and as P. griffithii Hook. f., but it seems rather to be a new species allied to P. surasiana Craib
from Thailand in having a very small ovary only a fraction of the size
of that of the species found to the west of Thailand. It
differs from P. surasiana in a number of important characters and seems to be a good new species (see fig. 3-17). The ovary of P. confertifolia is slightly less than a fourth as long as the style (see Swingle, 1940a, pl. 4, fig. 2).
12. Paramignya rectispinosa Craib, Kew Bul. Misc. Inform. 1916:261. 1916. Atalantia griffithii Craib (non Guill.), Aberdeen Univ. Studies 57:53. 1915 (?).
Type.—Thailand, Chiangmai, Doi Sutep (Kerr No. 1718). Herb. Kew.
Distribution.—Thailand.
[After Craib]: A climbing shrub with green, fleshy pubescent (soon puberulent twigs) [sic],
up to 3.5 mm diam., with axillary, straight or nearly straight,
pubescent spines nearly 2 cm long, green except for the straw-colored
tips; leaves oblong or oblong-oblanceolate, rigid, chartaceous,
obtusely-acuminate at the apex, gradually narrowed toward the rounded
base, 10.5-14 X 2.8-4.7 cm, blades glabrous above except for the midrib,
which is finely pubescent (very rarely subglabrous) especially at base,
soft-pubescent below, with many pellucid dots [oil glands], lateral
veins about 15 on each side, anastomosing inconspicuously, faint above
but prominent below; petioles 10-11 mm long, slightly channeled above,
pubescent like the twigs; flowers white (fide Kerr), solitary;
pedicels about 3 mm long, pubescent, with small branchlets near the
base; calyx 2 mm long, pubescent without, glabrous within, 5-lobed,
lobes deltoid or narrow-deltoid, rather obtuse, slightly shorter than
the tube; petals oblong, 12 X 3 mm, glabrous, conspicuously glandular
dotted; filaments 8 mm long, pubescent, glandular like the petals,
anthers 2 mm long; disk slightly shorter than the calyx; ovary about 1
mm long, densely pubescent; style 7 mm long, with divergent hairs;
stigma capitate.
Craib compared this species with P. griffithii Hook. f. [= P. scandens],
"from which it differs in having spines nearly 2 cm long, straight or
nearly straight." This species is known only from Craib's
original description, which shows it to differ markedly from the other
species of the genus, not only in the long, straight (or nearly
straight) spines, but also in its short calyx, very short ovary, and
short anthers. The type specimen was collected in evergreen
jungle at 660 m above sea level.
SPECIES OF DOUBTFUL RELATIONSHIPS
13. Paramignya cuspidata (Ridl.) Swing. Jour. Wash. Acad. Sci. 28:533. 1938. Atalantia cuspidata Ridl. Jour. Straits Branch Roy. Asiat. Soc. 82:174. 1920.
Types.—Malacca, Sungei Hudang (Ridley, No. 8391), and Dindings, Lumut (Ridley, No. 7944). Herb. Hort. Bot., Singapore.
Distribution.—Known only from the type localities in the Malay Peninsula.
The original description reads as
follows: "A spiny bush; branchlets pubescent; spines short, blunt,
straight. Leaves thin-textured, not coriaceous,
ovate-elliptic, cuspidate, blunt, base round, pubescent on the back,
midrib sunk above, elevated beneath, the nerves about 6 pairs, very
fine, forked at tip, 2-3 in. [5-7.6 cm] long, 0.5 in. [12 mm] wide;
petiole 0.2 in. [5 mm] long, pubescent, jointed in the
middle. Flowers solitary; pedicels 0.25 in, [6 mm]
long. Sepals round, pubescent. Petals 5, linear,
oblong, 0.4 in. [1 cm] long, white. Stamens linear,
oblong. Ovary cylindric, hairy. Style stout,
glabrous. Stigma orbicular. Fruit ovoid, blunt,
0.8 in. [2 cm] long; rind thin, pulp scanty; seeds 2, large flattened."
Thanks to the kindness of I. Henry
Burkill, former director of the Singapore Botanic Gardens, Swingle
secured a photograph from Kew Gardens of one of the type specimens
collected by H. N. Ridley (No. 7944) at Lumut, Dindings, March,
1890. A close study of this photograph shows that the
petiole is twisted just as those of other species of Paramignya,
because of a pulvinus just below the leaf blade, noted by Ridley who
stated: "petioles…jointed in the middle." This refers to the
junction of the pulvinus with the lower rigid portion of the
petiole. As the plant does not have recurved spines like
true species of Paramignya, it would seem at first sight not to belong in this genus. However, an inspection shows that P. cuspidata has
what seem to be leafy side branches that arise at right angles and
sometimes curve backward. The pulvinate pubescent petioles,
the recurved side branches, and the general character of the leaves seem
to indicate either an ancestral form from which the true Paramignya have evolved or else a degenerate form of Paramignya
that has largely lost its climbing habit and no longer has recurved
spines. This species is connected with the group of normal
long-spined species of Paramignya through P. lobata, which is a woody climber with short reverted spines.
14. Paramignya lobata Burkill, Gard. Bul. Straits Settl. 5:214. 1931. Atalantia hispida Ridl. (non Pierre), Fl. Malay Penin. 1:357. 1922; A. monophylla Ridl. (non DC.), Jour. Straits Branch Roy. Asiat. Soc. 26:26. 1894.
Type.—Johore, Tumpat near Kota Pahat (Lake and Kelsall. Nov. 11, 1892). Herb. Hort. Bot., Singapore. Cotype: Kelantan, Tumpat near Kota Bakru (Ridley, Feb., 1917). Herb. Hort. Bot., Singapore.
Distribution.—Malay Peninsula.
A climbing vine, with short (4-8 mm),
retrorsely curved, stout, sharp spines with strong bases oval in cross
section; twigs not angled but with slight longitudinal ridges, glabrous,
apparently also slightly glaucous, internodes 1-3 cm long; leaves thin
but more or less coriaceous, oblong-oval or long-elliptical, gradually
acuminate, the extreme apex of the acumen bluntly rounded or subacute,
bases broadly rounded or even slightly cordate, 6-12 X 2.2-5 cm, margins
subentire, slightly undulate, surface densely and evenly dotted with
oil glands, midrib depressed above, strongly salient below, lateral
veins faint above, and not strongly marked below, 12-15 pairs arising
from the midrib at an angle of 55°-60°, connected by coarsely reticulate
veinlets; petioles 5-8 X 1-2 mm, wingless, but with a narrow furrow on
the upper surface, glabrous, not clearly articulated with the leaf blade
and not jointed in the middle, the entire petiole more or less
pulvinoid and able to bend and twist to put the leaf blade in proper
position to catch incident light; flowers solitary, axillary; sepals 5,
oblong-acute, becoming triangular, ciliate or velvety-pubescent without;
petals 5, elliptic, slightly pubescent without, 7-8 mm long; stamens
10, filaments free, velvety-pubescent; disk a cylindric gynophore,
velvety-pubescent; fruits red, thin-walled, 1-1.5 cm long, 1-2 cm diam.,
deeply 2-5-lobed, depending on the number of seeds formed; pedicels 6-8
X 0.7-1.5 mm, more or less longitudinally ridged in the dried
specimens; seeds about 9 X 6 X 4 mm, apparently monoembryonic.
Thanks to the courtesy of R. E. Holttum,
then director of the Botanic Gardens, Singapore, who sent two type
specimens on which this species was based, Swingle had the best possible
material to study except for the flowers, which are known only from
Ridley's description of this plant cited above. The
strikingly lobed fruits of this species are quite unlike those of any
other species of Paramignya, and are for that matter unique in the tribe Citreae, although they are somewhat similar to the lobed fruits of Murraya gleniei of the tribe Clauseneae.
Paramignya lobata resembles the shrubby P. cuspidata in
having short, stout spines. Both of these species need
further detailed study to determine more definitely their true
affinities.
15. Paramignya trimera (Oliv.) Burkill, Gard. Bul. Straits Settl. 5:213. 1931. Atalantia trimera Oliv. Jour. Linn. Soc. Bot. 5(2):24. 1861; Triphasia monophylla DC. 1824; Atalantia (?) recurva Benth. 1863.
Type.—East Indian Archipelago, Timor Island (L'Eschenault, Tanaka's Det. No. Q-1719). Herb. Kew.
Distribution.—Java; southern Philippines: Mindoro and Mindanao islands; Timor; northeastern Australia.
A very full description of this species
based on material from Timor (the type locality) published by Decaisne
(1834, v. 439) under the name Triphasia monophylla D. C., reads
in translation as follows: "Twigs erect, rounded, bark glabrous,
verrucose, yellow-gray when young, becoming green. Leaves
simple, 1-2 in. [2.5-5 cm] long, 3/4 in. [18 mm] wide, oblong-ovate,
subentire, sometimes emarginate at the apex, midrib prominent below,
coriaceous, shiny, punctate with numerous pellucid glands, petiolate;
petiole 4 -2 lin. [8-4 mm] long, somewhat glabrous.
Spinescent stipules [spines] acute, 4-6 lin. [8-12 mm] long, horizontal,
with a greenish cortex, becoming gray. Inflorescence
racemose, axillary, half as long as the leaves, 8-2 flowers; pedicels
very short, somewhat glabrous, with 3 bracts. Calyx
persistent, 3-toothed, glandular-punctate, with subrounded teeth,
concave, margin ciliolate. Petals 3, rarely 4, alternating
with the calyx, 2 lin. [4 mm] long, obovate, concave, subcoriaceous,
without veins, glandular, punctate in the middle, smooth.
Stamens 6, shorter than the petals, filaments thick, flattened at the
base, free, without glands, equaling the ovary in length.
Anthers oblong-sagitate, obtuse at the apex, subglandular, punctate,
longitudinally dehiscent. Pistil almost equal to the stamens
in length. Ovary borne on a subsinuate disk, more or less
cone-shaped, 2-locular, 1 pendent ovule in each locule.
Style thick, glandular-punctate like the ovary. Stigma
flattish, obscurely 3-lobed. Fruit (immature) fleshy,
obovoid, crowned at the tip with the persistent stigma, filled with gum,
2-locular, 1 seed in each locule, seeds attached at the internal angle
of the segments."
A specimen collected on Mataja Island,
Mindanao, Philippines, by Kienholz (Bur. Sci., Manila, No. 15525, in
Herb. Univ. Calif.), was assigned to this species by Tanaka (1932e,
p. 427). It has leaves 8-10 X 5-6 cm, oval in outline,
broadly rounded at the apex, and rather abruptly emarginate; the
wingless petioles, 5-7 mm long, are not articulated with the blade,
wrinkled when dry, doubtless pulvinoid in the fresh state.
At each node is found a single short sharp recurved spine, 5-7 mm
long. The young ovaries are stipitate at the base, ovoid in
outline, tapering into a very short style, less than 1/4 the length of
the ovary, which is 2 mm long and 1 mm wide. The leaves are
much larger than those reported by Decaisne from Timor.
This species of Paramignya is an
anomalous one and may prove not to belong to this genus. It
has, however, recurved spines and a cylindrical gynophore like Paramignya. The locule walls seems [sic] to have minute hair-like secreting emergenzen unlike any other member of this genus yet studied.
Subtribe 2. Citrinae: Citrus Fruit Tress
The thirteen genera of the subtribe
Citrinae (the Citrus Fruit Trees), which include sixty-five species,
differ strikingly from the other members of the orange subfamily in
having pulp-vesicles, very peculiar structures that arise from the
locule walls (especially the dorsal wall) and grow into the locular
cavity, developing into sacks filled with numerous large, very
thin-walled cells full of a watery juice. No such structures
are found in any other plants of the family Rutaceae or in related
families, and no close homologies are known among any of the higher
plants. Other genera of the subfamily Aurantioideae have
secretory glands on the locule walls, from which arises the mucilaginous
gum that fills the locular cavity of the ripe fruit in most of the
genera.
The taxonomic work that has been done
since the beginning of this century on the genera most closely related
to Citrus has shown that the pulp-vesicles not only are of primary importance in the classification of the very close relatives of Citrus (the True Citrus Fruit Trees)7
but are even more important in the taxonomic study of the genera
included in the Near-Citrus Fruit Trees and in the Primitive Citrus
Fruit Trees. The presence or absence of pulp-vesicles is
indeed of paramount importance in the correct classification of the
small-fruited Citrus relatives and has permitted making a sharp
distinction between the two groups of small-fruited members of the
subtribe Citrinae and the deceptively similar Minor Citroid Fruit Trees
belonging to the subtribe Triphasiinae.
The thirteen genera of the subtribe
Citrinae fall naturally into three groups, A, B, and C.
Group A, which we may call the Primitive Citrus Fruit Trees, comprises
five genera, Severinia, Pleiospermium, Burkillanthus, Limnocitrus, and Hesperethusa. Pleiospermium has pulp-vesicles that are small, ovoid or cylindrical, blunt-tipped, and usually distinctly corticated. Limnocitrus
has pulp-vesicles that are slender, fusiform, with very acuminate tips,
somewhat contracted at the base where they are attached to the dorsal
wall of the locule. Severinia and Hesperethusa
have peripheral pulp-vesicles that are irregular in shape and size and
little differentiated in structure. Finally, Burkillanthus,
which is a very strange genus, has pulp-vesicles of a type not found as
yet in any other plant in the orange subfamily. The walls
of the pulp-vesicles are rather thick and semitranslucent.
As the fruit ripens, the pulp-vesicles apparently collapse entirely and
may perhaps set free a mucilaginous fluid. Burkillanthus has leaf, spine, and flower characters greatly resembling those found in the genus Pleiospermium,
from which it differs chiefly in having much larger fruits with a tough
rind and in having very numerous ovules (22 to 26) in each of the five
locules, instead of two ovules as in Pleiospermium. Probably Burkillanthus arose from a Pleiospermium-like ancestral form.
Group B, the Near-Citrus Fruit Trees, comprises two genera, Citropsis and Atalantia,
both showing well-organized pulp-vesicles with broad sessile bases and
slender conical sides tapering to a rather acute apex pointed toward the
center of the fruit.
Group C, the True Citrus Fruit Trees,
includes six genera with highly organized pulp-vesicles that show a
slender stalk at the base (except Clymenia) and a more or less expanded fusiform body with the apex more or less acutely pointed. The genus Clymenia
has short, often subglobose pulp-vesicles with short, usually very
broad stalks or almost sessile. Nevertheless, in all its
other characters, Clymenia is a True Citrus Fruit Tree, greatly resembling Citrus in external character, with simple leaves like those of Citrus medica but with venation somewhat like that in leaves of Wenzelia and Monanthocitrus of the subtribe Triphasiinae.
The genus Hesperethusa in group A resembles Citropsis
in group B in its leaf and seed characters but has much smaller fruits
with much less definitely organized pulp-vesicles. The genus
Atalantia of group B resembles the genera Fortunella and Eremocitrus of
group C in having small fruits with few locules, each containing only
one or two ovules. All the other genera in group C have
larger fruits, with four or more (usually six or eight) ovules in each
locule.
The twelve genera that, with Citrus, constitute the subtribe Citrinae are of extraordinary interest since all of them are undoubtedly rather closely related to Citrus.
Some of them throw light on the origin and evolutionary development of
the True Citrus Fruit Trees, as they represent more or less accurately
the remote ancestral forms from which Citrus arose.
Every effort has been made to discover all possible characters that
serve to demonstrate the evolutionary progress and present relationships
of these plants. For this reason tens of thousands of
serial microtome sections were made by the modified Juel technique from
herbarium specimens. The new characters thus revealed have
made possible the taxonomic placement of many genera and species up to
now only imperfectly known, and sometimes known only from a single
scanty herbarium specimen. For example, in all the
herbariums of the world, the new genus Clymenia, closely related to Citrus, and the new species Citropsis tanakae
were each represented by a single specimen, each having only a single
flower bud. Nevertheless, by application of the modified
Juel technique, it was possible to classify both of these plants with
certainly.
Thanks to this minute and detailed study
of all known plants of the subtribe Citrinae, a study that has extended
over many years, it became possible to discuss, with all pertinent
evidence assembled, the phylogeny of the True Citrus Fruit Trees, a
problem of great scientific interest because of the highly specialized
pulp-vesicles filled with fragrant, delicious juice. In the
orange subfamily these organs are found only in the subtribe Citrinae
and in full perfection only in the genus Citrus; nor are they
known to occur in any other of the half-million or so species of higher
plants now recognized by taxonomic botanists. Keys to the groups and genera of the subtribe Citrinae are presented.
GROUP A. THE PRIMITIVE CITRUS FRUIT TREES
This group includes the five genera of the subtribe Citrinae, Severinia, Pleiospermium, Burkillanthus, Limnocitrus, and Hesperethusa,
which show the most primitive pulp-vesicles, lacking the stalks of the
pulp-vesicles of group C (the True Citrus Fruit Trees) and the definite
conical shape with broad sunken bases of those of group B (the
Near-Citrus Fruit Trees).
Until three decades ago, taxonomists had
not realized that the plants belonging to these five genera contained in
their fruits various primitive forms of pulp-vesicles, those very
remarkable structures heretofore known only in the True Citrus Fruit
Trees, where they attain their most perfect development, and in the
obviously related Near-Citrus Fruit Trees, where they are somewhat
simpler but still impossible to overlook. As a result of
this discovery, made during the original preparation of this chapter,
these five genera were transferred to the subtribe Citrinae and took
their place among the near relatives of Citrus.
Severinia has six species, all
with simple leaves and with a cup-shaped disk in which the base of the
ovary is partially immersed. The very primitive pulp-vesicles are peripheral and much like those of Hesperethusa described below.
Pleiospermium has five species:
one with trifoliolate leaves, rarely with two leaflets or even one;
another species with usually unifoliolate or difoliolate leaves, rarely
with three leaflets; the third, fourth and fifth species always with
unifoliolate leaves. All these species have winged petioles
that are rather long (one-eighth to one-sixth the length of the leaf
blade) and articulated with the blade. The locules of the
fruit contain numerous small, ovoid or cylindrical pulp-vesicles, with
bluntly rounded or acute tips, usually having an outer cortical shell of
coarser tissue surrounding a central core of more delicate tissue that
seems to disintegrate, as the fruit ripens, into a more or less spongy,
oily, or resinous mass.
Burkillanthus looks like a Pleiospermium with giant, hard-shelled fruits. The uni-, di-, or trifoliolate leaves resemble those of Pleiospermium dubium but are larger; the petioles are narrowly winged and articulated with the leaflets, as in all the species of Pleiospermium. The flower is larger than in Pleiospermium
and the ovary is very different in morphology, having 22 to 26 ovules
in each of the five-locules, the largest number known in any plant of
the orange subfamily. The fruits of Burkillanthus are much larger than those of Pleiospermium
and also differ in having a firm leathery or woody rind.
They contain very numerous, very large seeds and peculiar thick-walled
pulp-vesicles that seem to secrete a mucilaginous fluid. Burkillanthus is probably descended from a Pleiospermium-like ancestor but has become so different as to constitute a very distinct genus.
Limnocitrus also resembles Pleiospermium
slightly but differs in having thick, veiny, simple leaves with very
short petioles (one-tenth as long as the leaf blade) that are pulvinoid
for their whole length. The ovary differs strikingly from
that of Pleiospermium. The fruits of Limnocitrus differ from those of Pleiospermium in
having very numerous, very slender, fusiform pulp-vesicles contracted
at the base into a short, broad stipe; they also show a central core of
whitish droplets of oil (or wax?). These pulp-vesicles do
not show the clearly corticated structure of those of Pleiospermium, or the irregular outlines of those of Hesperethusa, which are also much larger and fewer.
Hesperethusa presents striking analogies in its leaf characters with Citropsis, the African cherry-oranges. The pulp-vesicles in Citropsis are, however, much more highly organized than those of Hesperethusa, and show a high specialization of both structure and arrangement in the locule. The pulp-vesicles of Hesperethusa are
irregularly rounded or even polygonal from natural pressure, without
specialization of form or regularity of arrangement as far as can be
learned from the material now available for study. Hesperethusa, like Citropsis, can be grafted on Citrus, and vice versa.
This group of Primitive Citrus Fruit
Trees offers promise of throwing light on the origin and evolution of
the pulp-vesicles, unique organs that are found only in the subtribe
Citrinae and that reach their highest development in the genus Citrus and the other closely related genera comprising the True Citrus Fruit Trees.
In the course of a comparative study of
the vascular traces of the flowers of all obtainable genera of the
orange subfamily, Tillson (1938, pp. 12 and 25; see also Tillson and
Bamford, 1938, pp. 787 and 791) found that all the genera comprising the
Primitive Citrus Fruit Trees show fusion of the lateral sepal bundles
with the petal midrib. This unusual type of floral vascular
anatomy is found elsewhere in Luvunga and Paramignya, in the species of Citrus belonging to the subgenus Citrus (comprising all the commonly cultivated citrus fruit trees), and in Swinglea.
XIV. Severinia Tenore
XIV. Severinia Tenore, Ind. Sem. Hort. Neap. 3. 1840; also in Atti Terza Riunione Degli Sci. Ital. 502. 1841. Helie Roem. Syn. Hesper. 1:42. 1846.
Type species.—"Citrus buxifolia Hort." = C. buxifolia Poir., in Lamarck, Encycl. Meth. 4(4):580 (1797) = Severinia buxifolia (Poir.) Tenore, loc. cit.
Distribution.—Southern China, Malay Peninsula, East Indian Archipelago to the Philippines, Kei Islands, and New Guinea.
Common name.—Box-orange or severinias.
Leaves simple, conspicuously
parallel-veined, with very short wingless petioles 1/15-1/10 the length
of the leaf blade, not articulated with it; flowers small; in simple
clusters in the leaf axils or in corymbs or panicles; sepals 3-5-lobed;
petals 3-5; stamens 6-10, free; disk cup-shaped, enclosing the base of
the ovary; ovaries with 1-5 locules, with 1 ovule pendent in each
locule; fruits small, berry-like and juicy or semidry with a
well-defined peel dotted with oil glands; locules with rudimentary
pulp-vesicles, polyhedral through mutual pressure, often crushed by the
developing seeds; seeds smooth, plump, single in each locule.
The types [sic] species and all the other species here referred to as Severinia have in recent decades been considered to be species of Atalantia. Atalantia, however, differs decidedly from Severinia in
having well-formed, conical pulp-vesicles and much larger flowers,
often with the filaments of the stamens more or less
connate. The typical species of Severinia have the ovary more or less sunken in the disk, which is, in consequence, usually broader than the ovary. As noted above, Severinia has very primitive, stalkless, peripheral pulp-vesicles very like those of Hesperethusa; in neither genera is there indication of the contents breaking down into a more or less resinous mass, such as is seen in Pleiospermium. Severinia differs decidedly from Hesperethusa in having simple leaves and wingless petioles. The leaves of Severinia are strongly veined, the finer veins forming more or less uniform reticulations, not clearly marked in Hesperethusa. A still more striking difference is in the disk, which is cup-shaped in Severinia and annular in Hesperethusa. Severinia resembles Atalantia in
the shape, size, and venation of its leaves and in having wingless
petioles, but differs decidedly in having nonarticulated petioles and
more primitive pulp-vesicles without definite form, those of Atalantia
being conical and pointing toward the center of the fruit with a rather
broad base, more or less sunken in the tissues of the dorsal locular
walls. Severinia also resembles somewhat several of the genera in the subtribe Triphasiinae, especially the genera Paramignya and Pamburus, from which it differs in possessing rudimentary pulp-vesicles.
Severinia lauterbachii is very different from the first five species of the genus and is as yet only imperfectly known.
Severinia buxifolia and S. disticha are known to have served as rootstocks for Citrus, and it is probable that other species can be so employed.
The six species of Severinia are keyed.
1. Severinia buxifolia (Poir.) Tenore, Ind. Sem. Hort. Neap. 3 (?). 1840; also in Atti Terza Riunione Degli Sci. Ital. 501-503. 1841. Citrus buxifolia Poir. in Lamarck, Encycl. Meth. 4:580. 1797; Limonia monophylla Lour. (non L.) Fl. Cochinch. 1:271. 1790; Citrus emarginata Desf. 1829; Limonia bilocularis Roxb. 1832; Sclerostylis atalantioides Wt. & Arn. Prodr. 93. 1834; Atalantia loureiriana Roem. Syn. Hesper. 1:44. 1846;8 Helie atalantioides (Wt. & Arn.) Roem. Syn. Hesper. 1:42. 1846; Sclerostylis buxifolia Benth. Hook. Jour. Bot. 3:326. 1851; Atalantia buxifolia Oliv. Jour. Linn. Soc. 5 (Suppl. 2):26. 1861; Severinia monophylla ("L.") Tan. Bul. Mus. Hist. Nat. Paris, 2 ser. 2:163. 1930.9 Illus.
Seemann, Bot. Voy. Herald, pl. 81. 1852-1857; Penzig, Studi Bot. Sugli
Agrumi, Atl. pl. 11, figs. 6-17; pl. 12, figs. 1-21. 1887; Swingle,
Jour. Wash. Acad. Sci. 5:656, 657, figs. 1, 2. 1916; Tillson & Bamford, Amer. Jour. Bot. 25:784, figs. 21-25. 1938; fig. 3-18 this work.
Type locality.—In the vicinity of Canton, China (Sonnerat). Herb. Mus. Nat., Paris.
Distribution.—Southern China: Kwangtung Province, Hainan Island; North Vietnam; South Vietnam; Taiwan; Hong Kong; Cambodia; Laos.
Common name.—Chinese box-orange.
Bentham's description (1851, p. 326) may
be translated as follows: "Low shrub, or in our gardens dwarf tree,
branches spreading, young twigs obscurely angular or somewhat
compressed, always puberulous, soon glabrous and terete.
Spines axillary, strong, usually much shorter than the leaves, only
rarely longer. Leaves 1-1 1/2 in. [2.5-3.8 cm] long, 6-9
lin. [12-18 mm] wide, obtuse, narrowed at the base into a short, narrow,
rounded petiole, coriaceous, rigid, densely dotted with oil glands,
glabrous, with numerous parallel veins arising from the midrib, much
more conspicuous than in many species [of Sclerostylis = Atalantia].
Flowers between small bracts in the axils of the leaves, sessile, or
rarely borne on a very short pedicel, never solitary, usually
2-3-fasciculate. Calyx widely campanulate, short, smooth,
with 5 rounded, very obtuse lobes. Petals 5, scarcely 2 lin.
[4 mm] long, oblong, erect, glabrous. Stamens 10, shorter
than the corolla, filaments dilated, attenuate at the apex, anthers
ovate, parallel locules. Ovary sessile on a cupulate disk,
subglobose, fleshy, with small locules in the centers, ovules attached
to the central axis slightly below the apex. Style very
short, stigma thick, ovoid, pulvinate. Berry depressed
globose, becoming black at maturity, seeds large, ovoid."
The original description of Poiret (1797, pp. 580, 581) reads, in translation, as follows: "Citrus buxifolia,
leaves subsessile, ovate-retuse, flowers racemose, very small…I do not
know its height, but the branches I have examined in the herbarium of
Citizen Lamarck, would indicate that it is not tall. With
its short, stiff branches, its spines and the shape and firmness of its
leaves, it has the aspect of Rhamus pyracantha. The
wood is hard, white, with a smooth green bark. It has many
spreading branches with stiff straight spines, yellowish at the
tips. The leaves are few, alternate, oval, almost sessile,
much like those of box, but twice as large, obtuse at the apex,
emarginate, narrowed at the base, remarkable by the very close veins,
which are prominent and parallel, coriaceous, with entire
margins. The petioles are simple and very short.
The flowers occur in small bunches toward the ends of the
branches. The corolla is white and very small.
This plant is native to China and was observed there by Sonnerat, who
sent the specimens to Citizen Lamarck."
This, the type species of the genus Severinia,
is not an uncommon plant in wooded areas in southern China as far north
as the Tropic of Cancer. It is also found in Hong Kong and
Hainan, and in Indo-China from the northern border of Laos and North
Vietnam to latitude 10° S. It is a small, spiny tree with
crooked, thorny branches and dense, evergreen foliage (see fig. 3-18).
It is esteemed by the Chinese for its leaves, which are used in making
yeast cakes. For this reason it is called 'tsau 'ping lak10 in Cantonese, meaning "wine cake thorn."
A careful search for variations in S. buxifolia,
made by G. W. Groff and F. A. McClure, formerly of the Horticultural
Department of Lingnan University at Canton, led to the discovery of many
forms of the species differing in height, character of growth, size and
shape of the leaves, number and length of spines, et cetera, and also
in physiological characters, such as congeniality with Citrus in
grafting experiments. So far, none of these forms have been
given taxonomic names, but some appear so distinct that when they are
studied more carefully it may prove desirable to recognize them as
subspecies, varieties, or forms.
Certain broad-leaved forms growing near
the seashore at Da Nang (Tourane) in South Vietnam (Lat. about 16° N.)
have shown not only great vigor under culture but also high resistance
to boron and injurious saline solutes often found in the ground water
where Citrus is grown in semiarid situations.
Inasmuch as Citrus can be grafted readily on S. buxifolia,
and since some plants so grafted have lived over thirty years without
showing any sign of bad graft union, it is clear that more study should
be given to the use of this species as a rootstock. Besides
its important physiological distinction from Citrus in respect to boron
absorption and sensitivity toward saline solutes in the ground water,
the very fact that S. buxifolia is so remote a relative of Citrus as to be quite immune to many Citrus diseases recommends it for trial as a rootstock.
With regard to the relative boron
tolerance of the lemon and the box-orange, Eaton and Blair (1935, p.
413) stated: "The lemon (Citrus limonia Osbeck) is highly
sensitive to boron; in fact few plants are thought to be more sensitive,
and it accumulates much boron in its leaves. The Chinese
box orange, Severinia buxifolia, on the other hand, in
confirmation of the observations of Swingle, Robinson, and May, is
relatively tolerant to boron. Severinia has been found to accumulate much less boron in its foliage than does the lemon."
Eaton and Blair conducted experiments on
boron tolerance of the lemon and of the Chinese box-orange, as well as
of reciprocally grafted plants (i.e., lemon on box-orange roots and
box-orange on lemon roots) which Swingle supplied them with the help of
Eugene May, Jr. Striking proof that the box-orange has much
higher resistance to boron-poisoning than the lemon is given in their
Table II reproduced below (table 3-2).
Eaton and Blair commented as follows on
the data presented in the table: "Lemons [grafted] on box orange roots
had about one-third as much boron in their leaves as when grown on their
own roots. The data indicate that the boron concentrations
in the box orange leaves are increased threefold when the plant is grown
on lemon roots. There were no box orange plants on their
own roots in the 2 and 4 ppm cans, but the plant in 6 ppm on its own
roots had 390 ppm, whereas the box orange on lemon roots in 4 ppm had
877 ppm of boron in its leaves. Lemon leaves on their own
roots were more severely injured than when on the box orange roots."
This record of experiments, made after years of experience in growing Citrus
in nutrient solutions containing known amounts of boron, is of great
value in showing the striking difference in the toxicity of boron for Citrus roots and for Severinia
roots, although both genera of plants grow wild in situations that are
similar with respect to both climate and soils. (See also
discussion of boron tolerance of Eremocitrus.)
The possibility of growing Citrus on
a plant as remote, taxonomically, as the box-orange has served to
direct attention to the need of testing all the wild relatives of Citrus in the hope of finding others able to thrive as the box-orange does, in physical and biological environments that Citrus roots cannot endure, and at the same time able to serve as rootstocks for the commonly cultivated species of Citrus.
1a. Severinia buxifolia brachytic form.
Common name.—Dense-leaved box-orange.
Twigs spineless or nearly so, internodes
very short, often less than 1 cm long; leaves densely crowded because of
the short internodes; flowers and fruits as in the species but produced
in less abundance.
This form, analogous to the myrtle-leaved variety of the sour or Seville orange, Citrus aurantium var. myrtifolia, is even more like the common box (Buxus sempervirens)
in general appearance than the normal form of the Chinese
box-orange. This dense-leaved variety is, like the parent
species, able to endure high temperatures, hot winds, and other
unfavorable climatic conditions that would injure or kill the true box
tree. It cannot, of course, endure severe cold, like the
common box, and is injured when the temperature falls as low as 14° F
(-10° C). This beautiful, vivid green, nearly thornless
shrub deserves careful trial as a substitute for the common box for
hedges in warm-temperature and subtropical climates.
This form seems to arise by mutation from
the mother species. As might be expected, intermediate
forms occur as, for example, the one shown in figure 3-18,
which has some nearly thornless branches and others with long spines
borne on the same plant. Even the typical forms of this
mutation are usually not entirely thornless but have short, slender
spines that are, however, so completely hidden under the very abundant
leaves that the spines are scarcely felt when a branch is
touched. Doubtless by careful selection superior,
dense-leaved, thornless forms of this variety can be developed that will
be of high ornamental value.
2. Severinia disticha (Blanco) Swing. Jour. Wash. Acad. Sci. 28:533. 1938. Limonia disticha Blanco, Fl. Filip. 356. 1837; L. corymbosa Bl. Fl. Filip. ed. 2. 251. 1845; Sclerostylis nitida Turcz. Bul. Soc. Nat. Mosc. 31:249. 1858; Atalantia nitida Oliv. Jour. Linn. Soc. 5 (Suppl. 2):25. 1861; A. disticha (Blanco) Merr. Phil. Gov. Lab. Bur. Bul. 27:28. 1905.
Type.—Wanting. Substitute type: Luzon (Merrill, Species Blancoanae, No. 594). Herb. Bur. Science, Manila.
Distribution.—Philippines: Luzon to Mindanao islands; Sabah (North Borneo): Banguey Island.
Common name.—Philippine box-orange.
Young twigs angular, sometimes with
scanty gray pubescence soon glabrous and terete, sometimes apparently
glabrous from the beginning; twigs spineless but occasionally with
paired, slender, sometimes pubescent, spine-like paraphylls rarely
equaling the petioles in length; leaves 3-8 (rarely 10-11) cm long by
2.5-4 (rarely 1.5-2) cm wide, oval, ovate-lanceolate or sometimes
fusiform, acuminate or acute at the apex, acumen often blunt and
frequently emarginate, narrowed gradually into a cuneate base which
merges into the petiole, margin subentire sometimes slightly crenulate
and frequently wavy in dried specimens, lateral veins visible above but
slightly more prominent below, extremely numerous, parallel, straight,
occasionally showing 15-20 pairs, arising at an angle of 55°-60° with
the midrib; petioles 3-9 (usually 6-8) mm long, flattened above with a
furrow made by the decurrent margins of the leaf, sometimes pubescent,
sometimes almost glabrous, especially on the under side; inflorescences
many-flowered, axillary or rarely terminal racemes, 3-6 cm long (rarely
8-9 cm long, and much branched); pedicels slender, 3-5 mm long, with
minute bractlets at their juncture with the peduncle; both peduncles and
pedicels pubescent; calyx persistent, sepals 5, imbricate, broadly
rounded, margins ciliate; petals 5, 3.5-4.5 mm long, 2-3 mm wide, oblong
or obovate; stamens 10, nearly as long as the petals, filament
flattened, broad, free, anthers short, small, ovate; ovary subglobose,
small (1.5-2 mm long), 2-locular, with 2 large glands at apex, 1 over
each locule; disk cupulate, partly enclosing the base of the ovary;
style as long or longer than the ovary, stigma ovoid, slightly broader
than the style; fruits subglobose, 6-8 mm diam. when mature, peel
yellowish-green, with many large, translucent oil glands, 0.5-0.75 mm
diam.; seeds thick, monoembryonic, testa exceedingly thin, embryo
olive-green when dry and covered with numerous minute oil glands, 0.1 mm
diam.
This species, very abundant in the northern Philippine Islands, is so like the box-orange, S. buxifolia, that when it was found the latter could be used successfully as a rootstock for Citrus tests were also made with S. disticha.
It was found to serve as a rootstock almost as well as the box-orange
and, like it, to be resistant to amounts of boron in the soil moisture
that would be injurious to Citrus grafted on the commonly used rootstocks belonging to the genus Citrus. Swingle made these tests over thirty years ago in a greenhouse at Washington, D.C. by watering potted seedling plants of Citrus, Severinia,
and other genera of the orange subfamily with water containing 2 ppm of
boron. Because of evaporation from the soil and
transpiration from the plant, the boron accumulated in the soil rather
rapidly and soon the Citrus seedlings showed the characteristic
yellowish-green mottling of the leaves, followed by severe injury and
even death. The seedlings of Severinia buxifolia and S. disticha remained healthy for many weeks after those of the Citrus species showed severe injury. Severinia disticha has fruited freely in Miami, Florida.
3. Severinia linearis (Blanco) Swing. Jour. Wash. Acad. Sci. 28:533. 1938. Limonia linearis Blanco, Fl. Filip. 357. 1837; Atalantia linearis Merr. Phil. Jour. Sci. 1 (Suppl. 3):200. 1906.
Type.—Wanting. Substitute type: Luzon, Rizal Prov. (Merrill, Species Blancoanae, No. 746). Herb. Bur. Sci., Manilla [sic].
Distribution.—Philippines: Luzon Island.
Common name.—Narrow-leaf box-orange.
Merrill's description of Atalantia linearis
reads as follows: "A shrub 1 to 3 m high. Branches light
gray, glabrous, the young branchlets greenish, pubescent or puberulent,
terete. Leaves alternate, linear to narrowly linear-oblong,
or linear-lanceolate, glabrous, shining, coriaceous, 2 to 7 cm long, 3
to 10 mm wide, the base acute, the apex blunt, retuse, entire, the
margins often somewhat recurved, the midrib prominent, the lateral
nerves numerous, scarcely more distinct than the dense reticulations;
petioles glabrous or pubescent, 3 mm long or less.
Inflorescence of terminal and axillary panicles, 3 to 5 cm long,
pubescent, the branches short, few-flowered. Flowers white,
short-pediceled, and 6.5 mm long. Calyx short, regularly
5-lobed, the lobes imbricate, broadly suborbicular, rounded, about 2 mm
long, 2.5 mm wide, pubescent, the margins ciliate. Petals 5,
free, oblong, the apex rounded, 6 to 6.5 mm long, and 3 mm wide,
somewhat narrowed at the base. Stamens 5 [10]; filaments
broad, 4 mm long; anthers about 1-4 mm long. Ovary glabrous,
3-celled, sessile, the disk shallow. Fruit glabrous,
globose, white, glandular-punctate, about 8 mm in diameter.…
"On cliffs and boulders at an altitude of
about 40 m along the river, frequently in situations submerged at high
water associated especially with Eugenia mimica Merr., and sometimes with Homonoya riparia
Lour.…A species at once recognized by its very narrow leaves, which are
retuse at the apex. Blanco's original description of this
species is very short, his material being from the Island of Maricaban,
Province of Batangas, Luzon, flowering in the month of July.
In this description he states that the leaves are minutely serrate,
probably from the fact that in specimens with recurved leaf margins, the
slightly raised veins on the upper surface appear like minute
teeth. The note following the description of the species in
the first edition of the Flora di Filipinas is excluded in the
second, this note referring to a similar form observed by Blanco in the
Province of Bulacan, Luzon. I am of the opinion that the
form here described is identical with Blanco's Limonia linearis, and accordingly his specific name is adopted and the species is redescribed under Atalantia."
This curious species is apparently a satellite species derived from S. disticha that
has become adapted to growing in situations exposed to
flooding. Perhaps the narrow leaves resist the tearing
action of flood waters rushing down narrow valleys. The
lateral veins of the leaves run less regularly parallel than those of
the leaves of S. disticha. Perhaps this, too, is an adaptation to prevent splitting of the leaves by rushing waters.
Extreme specimens of S. linearis are easily distinguished by the narrow leaves, but broad-leaved forms are hard to distinguish from narrow-leaved forms of S. disticha. A broad-leaved specimen of S. linearis (coll.
by M. P. Sulit, April, 1926; Tanaka’s ident. No. C-305, Forestry Bur.,
No. 30320, Herb. Univ. Calif.) has leaf blades measuring 9 to 11 cm in
length, and 1.5 to 2 cm in width! However, the venation of
the two species differs slightly, lateral veins of S. linearis running more irregularly and distinctly less parallel than those of S. disticha. It is possible that natural hybrids may be in play here.
4. Severinia paniculata (Warb.) Swing. Jour. Wash. Acad. Sci. 28:533. 1938. Atalantia paniculata Warb. Bot. Jahrb. 13:340. 1891; A. maritima Merr. Phil. Jour. Sci. Bot. 9:293. 1914; A. disticha var. paniculata Tan. Jour. Arnold Arbor. 9:141. 1928.
Type.—Ceram Laut (Warburg, No. 20132). Herb. Bot. Mus., Berlin-Dahlem.
Distribution.—Moluccas: Kei
Islands, Ceram Laut; southern Philippines: Mindanao, Negros, and Panay
islands; North Borneo (Sabah): Biak; Sumbawa and Java (fide Tanaka, 1928c, p. 141).
Common name.—Bouquet box-orange.
Warburg's original description of this
species reads in translation as follows: "A shrub with gray-pubescent
[terminal] branches, soon glabrate, with yellow wood; leaves
oblong-ovate, obtuse or emarginate at the apex, margin obscurely
crenulate; petioles short, pubescent, nearly terete; inflorescences
terminal, paniculate, pubescent, pedicels short; calyx 5-lobed, lobes
pubescent and ciliate, subtruncate at the tips; petals nearly glabrous,
lanceolate, obtuse; filaments long, glabrous, anthers broadly cordate;
ovary with 4 locules; style deciduous; fruits globose, with the calyx
persistent, 2-4-seeded. The youngest twigs are
reddish-yellow, the somewhat older twigs brown after the gray pubescence
has fallen, often with a whitish bloom; the petioles are 8 mm long, the
leaves 9-12 cm long and 3-5 cm wide, with a large number of parallel
veins of which some are more prominent, uniting near the margins in
arches. The whole inflorescence is 4-6 cm long, branched
from the base, the flower pedicels are from 2-4 mm long, the calyx is
about 2 mm long, the sepal tips 1 mm long, the petals and stamens are 4
mm long; the largest fruit of my specimen [Warburg, No. 20132] is 12 mm
in diameter."
This species is easy to distinguish from
the related species because of its pubescence, its lack of thorns, and
its terminal paniculate inflorescences.
Severinia paniculata was
discovered on Ceram Laut and Kei Islands in the Moluccas west of New
Guinea growing on dry areas in the brush. Tanaka considered
it to be identical with Atalantia maritima, growing in the southern Philippines, but Swingle could not follow him in making the species a variety of S. disticha,
although it is closely related to that species. It differs
in having larger leaves and smaller, paniculate rather than racemose
inflorescences, and in having ovaries with four instead of two locules.
5. Severinia retusa (Merr.) Swing. Jour. Wash. Acad. Sci. 28:533. 1938. Atalantia retusa Merr. Phil. Jour. Sci. 1(Suppl. 4):200. 1906.
Type.—Philippines, Palawan Island, Puerta Princessa (Curran, No. 3609). Herb. Bur. Sci., Manila.
Distribution.—Known only from the type locality.
Merrill's original description of this
species reads as follows: "A shrub about 3 m high, with
oblong-elliptical-ovate, subcoriaceous, glabrous, strongly retuse
leaves, racemose inflorescences and 5- to 7-merous, the stamens 10 to
15, free, the ovary 1-celled. Branches brownish-gray,
glabrous, the branchlets green, glabrous. Leaves 5 to 9 cm
long, 2.5 to 4 cm wide, shining, broad at both ends, scarcely narrowed
above, the base rounded; nerves numerous, anastomosing; petioles 8 mm
long or less, the spines short or wanting. Racemes in the
upper axils, 1.5 cm long in anthesis, densely flowered,
puberulent. Calyx lobed, the teeth 5 to 7, short, broad,
regular, their margins ciliate, obtuse. Petals 5 to 7,
glabrous, oblong, obtuse, 5 to 5.5 mm long, 2.5 mm wide.
Stamens 10 to 15, unequal, the filaments free, 2.5 to 3.5 mm long,
anthers broadly ovate, slightly exceeding 1 mm in length.
Ovary oblong, glabrous, 1-celled, 1-ovuled; style much shorter than the
ovary, including the stigma about 1 mm long. Disk thickened,
ring formed. Fruit (immature) ovoid, glabrous.
"A species apparently related to Atalantia disticha (Blanco)
Merr., differing from the latter in its leaves not being narrowed
above, and in its flower characters. In some cases a very
rudimentary second cell was observed in the ovary, showing that the
species is perhaps sometimes with 2-celled ovaries. The very
short style is another character, as well as the variable number of
calyx teeth, petals and stamens. In other species of the
genus the ovary is from 2- to 5-celled, the petals and calyx teeth 3 to
5, and the style equalling [sic] or longer than the ovary."
This species is described as having an
ovary with only one locule, but a specimen in the National Herbarium at
Washington, sheet No. 439318, from Palawan (J. Bermejos, Bur. Sci., No.
195), shows ovaries with two locules. Penzig (1887, p. 158)
reported finding, very rarely, ovaries of S. buxifolia that were "monocarpellate without the slightest trace of a second ovarial follicle." A specimen of Atalantia maritima (considered by Tanaka [1932e, p. 426] to be a synonym of S. paniculata)
in the National Herbarium at Washington, sheet No. 1294389, from
Zamboanga, Mindanao Island, P.I. (A. Lomente, Forestry Bur., No. 25288),
shows only a single carpel in the ovary and a single stylar
canal. Three of the typical species of Severinia occasionally (or regularly) show only a single locule in the ovary and probably the other closely related species, S. paniculata, may occasionally show a hypomerous or even a monocarpellate gynoecium.11
SPECIES OF UNCERTAIN RELATIONSHIPS
6. Severinia lauterbachii Swing. Jour. Wash. Acad. Sci. 28:533. 1938. Atalantia litoralis Lauterb. (non Guill.) Nova Guinea 14:146. 1924.
Type.—Northwestern New Guinea
[West Irian, Indonesia], Schouten Islands, Biak, near Warsa (Lat. 2° S.,
Long. 137° E.), growing on coral limestone strand (Feuilleteau de
Bruyn, No. 320). Herb. Bot. Mus., Berlin-Dahlem.
Distribution.—Known only from the type locality.
Common name.—Triangle-fruit severinia.
The original description, translated,
reads as follows: "Small tree, about 4 m high, with slender, flattened,
glabrous twigs, 4 mm thick. Leaves elliptic or broadly
lanceolate, subacutely rounded at the apex, sometimes emarginate or
subacute, base subacute, margins obscurely crenulate, 12-16 cm long, 6-8
cm wide, coriaceous, glabrous above and below, lateral veins 16,
obliquely subparallel, curved and anastomosing near the margin, veinlets
subparallel, reticulate, when dry more prominent below like the midrib;
petiole flattened on upper surface, 6-7 mm long.
Inflorescences axillary, paniculate, many-flowered, 3-6 cm long, small
branchlets minutely pubescent. Flowers pedicellate, pedicels
3-4 mm long; buds obovoid; calyx 5-lobed, lobes rounded, ciliate, 1 mm
long; petals 5, oblong, rounded, white, glandular, glabrous, margins
subpellucid, 5 mm long, 1.5 mm wide; stamens 10, 5 of them shorter, 3 or
5 mm long, both [lengths] connate at the base, filaments dilate,
glabrous anthers cordate, about 1 mm long; disk short, 10-crenulate;
ovary triangular, each angle crowned with a large gland, 3-locular, 1.3
mm long; style clavate, 2 mm long, stigma decurrent, somewhat 3-lobed."
This species was said by Lauterbach to differ from Atalantia paniculata Warb. (here S. paniculata)
in having much larger leaves and larger flowers with triangular
ovaries, each having three locules. The term "10-crenulate"
applied to the disk of this species probably indicates that it is
cupulate (as in other species of Severinia), but in drying it has
become separated from the base of the ovary and acquired a wavy
margin. It is possible that this curious species does not
belong to the genus Severinia, but it is impossible to place it with certainty until the flowers and fruits are better known.
Merope angulata, widely distributed in tidal swamps, also has triangular (sometimes 4- or 5-angled) fruits,
but it has very large seeds, stout paired spines in the leaf axils, an
ovary with two to four pendent ovules in each locule, and a cylindric
disk definitely not cupulate or 10-crenulate. Merope angulata is probably very different from S. lauterbachii, although the latter species is also a strand plant with triangular fruits.
This species was named Atalantia litoralis by Lauterbach in 1924, but this name was preoccupied by Atalantia littoralis (Miq.) Guill., a new combination made eleven years previously by Guillaumin (1913, p. 441) when he transferred Paramignya littoralis Miquel to the genus Atalantia. The variation in spelling, litoralis or littoralis,
does not make these names distinct, as these are merely variant
spellings of the same Latin adjective. Lauterbach's specific
name, therefore, has no standing and must be supplanted by the new name
which is used here.
XV. Pleiospermium (Engl.) Swing.
XV. Pleiospermium (Engl.) Swing. Jour. Wash. Acad. Sci. 6:426. 1916. Limonia Sec. Pleiospermium Engler, Die Nat. Pflanzenfam. 3(4):189. 1896.
Type species.—Limonia alata Wt. & Arn. = Pleiospermium alatum (Wt. & Am.) Swing.
Distribution.—Southern India, Ceylon, Sumatra, Java, Borneo.
Common name.—Orangeasters.
Small trees; twigs with 1 or 2 spines in
the axils of the leaves or unarmed; leaves 3-foliolate, 2-foliolate, or
1-foliolate, margins entire; petioles narrowly winged or nearly wingless
(broadly winged in P. latialatum); inflorescences axillary or
terminal panicles of few-flowered groups of flowers arising in the axils
of the leaves; flowers 12-24 mm diam.; calyx 4-5-lobed, sepals deltoid
or lanceolate-acuminate (in P. longisepalum, long, strap-shaped,
persistent, reflexed); petals 4 or 5, oblong or linear-oblong, rounded
at the tips, 6-12 mm long; stamens 8 or 10 (twice as many as the
petals), filaments free, glabrous; anthers oblong or linear-oblong;
pistil subsessile or short-stalked; disk cupulate, enclosing base of
ovary for 0.5-0.8 mm; ovary cylindric or ovate, with 4-5 locules, ovules
2 in each locule; style slender or thick, not sharply delimited from
the ovary, ending in a more or less capitate stigma with 4 or 5 stylar
canals, with 2 small oil glands between each pair; fruit globose or
oblong, 20-30 mm diam., with slender rudimentary pulp-vesicles, 2-10 mm
long, that are more or less corticated and show more or less
disintegration of the contents into an oily or resinous mass as the
fruits ripen; seeds about 1 cm long, flattened.
This genus includes some of the most
puzzling species of the subtribe Citrinae. These species
have been referred to several different genera, usually with a question
mark! None have been examined thoroughly in the living
condition and it is very desirable that a study be made of the structure
of the fruit and in particular of the peculiar pulp-vesicles, which at
some stages of their development have very much the appearance of
stalked oil glands.
The two always unifoliolate species from northeastern Borneo, P. longisepalum and P. latialatum, and the one from Sumatra, P. sumatranum, are somewhat like Atalantia
in appearance, but differ in having well-developed winged petioles
plainly articulated with the leaf blade, as in the two other species of Pleiospermium which have tri-, di-, or unifoliolate leaves. The very curious new genus Burkillanthus has a marked superficial resemblance to Pleiospermium in its leaf characters but differs widely in its fruits. It is probably a large-fruited form derived from a Pleiospermium-like ancestor.
The pulp-vesicles in the genus Pleiospermium, although very primitive in comparison with those of Citrus,
show a very interesting series of stages in the evolution of these
unique and taxonomically highly important organs. In P. dubium the
pulp-vesicles are long-ovoid or cylindrical, each with a very distinct
tissue surrounding a definitely limited central body that looks very
much like a rutaceous oil gland, and, like such an oil gland,
degenerates at length into a granular, apparently structureless mass of
oily or resinous (?) substance. In P. sumatranum the
pulp-vesicles are short, only about 1 to 2 mm long, with blunt tips, and
also are plainly corticated. The central mass of cells
breaks down into an unorganized mass that looks much like that of an oil
gland in the immature peel of a citrus fruit. The
pulp-vesicles of this species seem to secrete a liquid that fills the
locules of the fruit and hardens on drying to a dark reddish-brown,
brittle, resinous mass. In the two Bornean species, P. longisepalum and P. latialatum, the pulp-vesicles are longer than in P. dubium and much longer than in the similar-looking P. sumatranum,
and are of a slender conical shape often ending in a sharp point at the
apex. Their cortical tissue is much thinner than in P. dubium
and less clearly cellular. The constituents do not break
down so completely. The pulp-vesicles of these two species
are more like those of Citropsis and Atalantia but have
smaller bases not so deeply sunken into the dorsal wall of the
locule. The series of pulp-vesicles in the different species
of Pleiospermium connect with the still more highly developed pulp-vesicles of Limnocitrus, which are no longer conical but are definitely fusiform and do have a very short stalk.
Perhaps no other genus of the orange subfamily is of greater interest than Pleiospermium
in throwing light on the origin and development of the unique and
highly specialized pulp-vesicle organs which are found only in the
subtribe Citrinae, and which reach their highest specialization in the
genus Citrus, giving the delicious flavor characteristic of its
cultivated varieties. It would be desirable to study the
development of the pulp-vesicles in Pleiospermium and the related genera Limnocitrus and Burkillanthus from living material.
The discovery of three species of Pleiospermium having unifoliolate leaves greatly resembling those of Citrus in
shape, size, color, and texture brings them and their trifoliolate
congeners into prominent notice as possible persisting representatives
of ancient ancestral forms in the descent of Citrus. Like the living species of Citropsis in tropical Africa, the species of Pleiospermium show all stages in the origin of unifoliolate leaves from trifoliolate leaves (or pinnate leaves in Citropsis), something that without doubt occurred, ages ago, in the development of Citrus. A key to the species of Pleiospermium is presented below.
1. Pleiospermium alatum (Wt. & Arn.) Swing. Jour. Wash. Acad. Sci. 6:428. 1916. Limonia alata Wt. & Arn. Prodr. 1:92. 1834. Illus. Wight, Ill. Ind. Bot. 1:pl. 41. 1840; Beddome, Fl. Sylv. pl. 7, fig. 3(1-9). 1871.
Type.—Southwestern British India, "foot of the Neelgherries," Madras State (Wight, No. 324).
Distribution.—Western peninsular India: Madras State; Ceylon.
Common name.—Ceylon orangeaster.
Small trees with glabrous branchlets,
sometimes with a single stout, straight spine up to 25 mm long at the
side of the bud in the axil of the leaf, sometimes spineless, especially
the fruiting branches; leaves 3-foliate [sic] (rarely 2- or
1-foliolate); lateral leaflets much smaller, all leaflets rather thick,
glossy above, finely netted-veined beneath, lateral veins slender, not
very conspicuous, making a very wide angle with the midrib, margins
entire, the apex obtuse or subacute, rarely acuminate, bluntly rounded
at the very tip, often emarginate, the leaflet blade abruptly narrowed
to a cuneate base; petiole variable, 25-38 mm long, narrowly winged,
articulated with the blade; inflorescences in clusters in the axils of
the leaves or in terminal much-branched hoary panicles; flowers small,
about 12-15 mm diam., 4-5-merous, pedicels rather short, finely
pubescent; flower buds cylindric, rounded at the tip, more or less
pubescent; calyx small, 4-5-lobed, sepals deltoid, finely pubescent;
petals oblong or ovate, obtuse, entire, sparingly covered with fine
pubescence without; stamens free, 8 or 10 (twice as many as the petals),
filaments free, anthers large, erect, linear-oblong; pistil subsessile,
seated on a low cupulate disk which clasps the base of the ovary for
0.5-0.8 mm; ovary obovoid, glabrous, 3.5-4.2 X 1.6-1.8 mm, 4-5 locular,
with 2 ovules in each locule; style slender, gradually merging with the
tip of the ovary and capped by a slightly thicker, subglobose stigma;
fruits globose, 2.3-2.5 cm diam., like small oranges in appearance, the
segments each containing 1 or 2 seeds surrounded with an aromatic,
mucilaginous fluid, peel rough, dotted with numerous oil glands, seeds
ovate, somewhat flattened, with a hard, smooth testa.
This species occurs rather commonly in
the hot dry parts of southern India and Ceylon. The fruit is
said to be very bitter; the wood is hard and heavy, yellowish,
even-grained. The leaves have a strong lemon odor when
crushed.
2. Pleiospermium dubium (Bl.) Swing. Jour. Wash. Acad. Sci. 6:429. 1916. Limonia ? dubia Blume, Bijdr. Fl. Nederl. Indie 1:133. 1825; Paramignya blumei Hassk. Tijdschr. Nat. Gesch. 10:137. 1843.
Type.—Java, Kuripan (Blume), Rijks Herb., Leiden (sheet No. 908203-1318).
Distribution.—Java.
Common name.—Java orangeaster.
Twigs angular when young, with straight,
sharp spines, 2-2.5 mm long, 1 or 2 in the axils of each leaf, older
twigs often spineless; leaves 1-, 2-, or 3-foliolate; leaflets thin,
elliptical, cuneate at the base, acute or acuminate at the apex, the
very apex often blunt, or emarginate, the middle leaflet (or single
leaflet) 7-9.5 X 2-3.6 cm, with 8-12 faint veins visible on both
surfaces on each side; petioles 7-22 mm long, narrowly winged above but
nearly wingless at base, plainly articulated at both ends; flowers in
short, 5-15-flowered, axillary racemes; ovary obovoid, hirsute, 2-2.8 X
1.2-1.7 mm, borne on a cylindrical gynophore somewhat like that of Paramignya or Merope;
fruits with rudimentary pulp-vesicles arising from the ovary wall,
elongate-ovoid or irregularly conical, 2.5-3.5 mm long, 0.4-0.6 mm broad
at the base, completely covered with a cellular cortex which connects
at the base with the dorsal wall of the locule but is not usually
imbedded in it and never deeply imbedded; mature fruits subglobose,
2-2.5 cm diam.
This species, known only from Java, is of
great interest from the fact that, because of its leaves, which have
from one to three leaflets, it serves to connect the usually
trifoliolate Indian species, P. alatum, with the unifoliolate species, P. samatranum, P. longisepalum, and P. latialatum, which all have leaves remarkably like those of Citrus. This is true also of the unifoliolate leaves of P. dubium.
The pulp-vesicles of this species are
each sharply divided into a cortical layer, composed of rather small
cells, and a central portion made up of larger cells which finally
disintegrate into a spongy mass, oily or resinous (?) in nature, which
looks much like the contents of the oil glands in the peel of the young
fruit (see above).
Blume's type material was collected on
"limestone hills near Kuripan, Buitenzorg Prov." in Java, but neither
flowers nor fruits were mentioned by him. The type specimen
in the Rijks Herbarium at Leiden, No. 908203-1318, and a cotype specimen
in the Herbarium of the Museum of Natural History at Paris both show
trifoliolate leaves; the Leiden branch has paired axillary spines as
described by Blume, the Paris specimen is spineless.
Plants of P. dubium cultivated in
the Botanic Garden at Buitenzorg (now Bogor), Java, have flowered and
fruited for many years. Dried herbarium specimens from these
trees were distributed by B. P. G. Hochreutiner, as No. 111 in his Plantae bogorienses exsiccatae,
about 1904 (this number is found in the Kew Herbarium and also in the
Paris herbarium). On his printed label Hochreutiner stated:
"This plant is without any doubt the original of Hasskarl['s Paramignya blumei]" (Swingle, 1916b,
p. 429). Herbarium specimens from these Buitenzorg plants
are preserved in the herbarium of the Bureau of Science at Manila and in
the National Herbarium (sheet No. 448333) at Washington.
From them were taken the flower and fruit characters given in the
description above.
Pleiospermium dubium is a small
tree or shrub, attaining a height of about 4 meters. The
inflorescences were said by Koorders (1912, p. 426) to be 5 to
15-flowered, short, axillary racemes. This plant has
probably the most polymorphic foliage of any species of the orange
subfamily. It often has branches bearing only trifoliolate
leaves and others with exclusively unifoliolate leaves.
However, sometimes trifoliolate and unifoliolate leaves are disposed
hit-and-miss on a branch. Some trifoliolate leaves develop
only one of the side leaflets.
This species and Citropsis gabunensis
of tropical West Africa, which has almost equally polymorphic leaves,
offer excellent material for a study of the critical evolutionary stages
passed through ages ago by the remote ancestors of Citrus.
3. Pleiospermium sumatranum Swing. Jour. Arbor. 20:260. 1939. Illus. Swingle, loc. cit. pl. 3, figs. 3, 4; fig. 3-19 this work.
Type.—Sumatra, Paanus (?) (Korthals, No. 960). Rijks Herb., Leiden.
Distribution.—Known only from Korthals' collections, probably from a single locality.
Common name.—Sumatra orangeaster.
Shrub or small tree; twigs cylindrical,
slender (1-2 mm diam.), brownish-gray (in dried herb. spec.), fruiting
twigs spineless, internodes 2-3 cm long; leaf blades broadly lanceolate,
8-17 cm long, 5-8 cm wide, acuminate at apex, acumen about 9-13 mm
long, often curved slightly to right or left, 3-4.5 mm wide at base, but
at the very tip 1.5-2 mm wide, blunt or slightly emarginate, base
cuneate (angle 75°-85°), blade 10-16 X 5-6.5 cm, petiole 18-20 mm long,
winged above, 3.5-6.5 mm wide, but wingless for 4-5 mm up from
attachment at base, lateral veins 10-12 but of unequal prominence, some
strongly elevated above lower surface, others faint and not prominent,
making angles of 60°-75° with the midrib, margins entire, very faintly
undulate, oil glands very numerous, evenly spaced all over the blade,
0.2-0.5 mm apart, plainly visible below, almost invisible above,
petioles 10-20 mm long, 3-7 mm wide, winged at top, wingless at base;
inflorescences axillary, simple or rarely bifurcate, apparently
sometimes terminal on short lateral twigs; pedicels of nearly ripe
fruits 1-1.5 cm long, 2-3 mm wide; flowers unknown; calyx with 5 acute
lobes, 1-2 mm wide and 2-2.2 mm long, minutely pubescent below, margins
sparingly short-ciliate; fruits subglobose, 18-20 mm diam., with 3
locules lined with a dense layer of short pulp-vesicles, 1-2 mm long,
0.4-0.7 mm wide, peel with numerous oil glands 1.5-1.8 mm thick.
This species of Pleiospermium has
remarkably small pulp-vesicles lining the dorsal walls of the three
locules of the fruit. The pulp-vesicles are very numerous,
ovoid, bluntly rounded at the tip, 1 to 2 mm long, 0.4 to 0.7 mm wide,
slightly narrowed at the base but not imbedded in the locule wall,
cortex very thin, composed of indistinct cells, contents sharply
delimited from the cortical layer and soon breaking down into a spongy
mass of oily or resinous (?) matter looking almost exactly like the
contents of the oil glands in the peel of the fruit (see fig. 3-19).
Apparently these very small pulp-vesicles secrete a translucent liquid
that completely fills the locules of the fruit. In dried
herbarium specimens this liquid hardens to a dark reddish-brown,
resin-like mass that splinters when struck a sharp blow.
This Sumatran species of Pleiospermium and its two close relatives from Banguey Island and Borneo, P. longisepalum and P. latialatum, all have leaves very similar to those of Citrus except for the more or less acuminate leaf tips.
A fungus, found on the fruits of the type
specimen, was identified by Bitancourt and Jenkins (1938, p. 388) as a
species of Elsinoë much like the scab fungi, E. fawcettii and E. australis, that attack Citrus.
4. Pleiospermium longisepalum Swing. Jour. Arnold Arbor. 20:259. 1939. Illus. Swingle, loc. cit. pl. 3, fig. 5.
Type.—Banguey Island (off
northeastern point of Borneo) (Castro and Melegrito, No.
1348). Herb. Natl. Arbor., Washington, D.C. (sheet No.
45800).
Distribution.—Known only from the type collection and from Castro and Melegrito, No. 1713, from the same locality.
Common name.—Banguey Island orangeaster.
A small tree or shrub, fruiting twigs
angular, 2-3 mm diam., straight, glabrous, grayish-green, spineless,
vegetative twigs at first angular then cylindric, 2-3 mm diam., both
vegetative and fruiting twigs with faint striae decurrent from the
nodes; leaves 1-foliolate, leaf blades 7.5-11.5 X 3-4.5 cm, elliptical
with acuminate apices turned slightly to one side, but the actual tip
(about 2 mm wide) abruptly rounded or even slightly retuse, margins
entire, lateral veins weak, 8-10 irregular pairs, with irregular
reticulations between; petioles 10-14 mm long, clearly articulated with
the leaf blades and with the twigs, winged, 3-5 mm wide at top, tapering
into a wingless base constituting about 1/4-1/3 the total length,
wingless basal portion often twisted and apparently pulvinoid; flowers
borne singly in the axils of the leaves but the tip of flowering branch
merging into a racemose inflorescence with the leaves reduced or
wanting; pedicels 20-25 X 1.5-2 mm with several minute bracts borne
singly, faintly striate longitudinally and grayish-green like the twigs;
pedicels of sterile flowers persistent, very slender, 15-20 X 0.75-1
mm; sepals persistent, gray-green, strap-shaped, 9-12 mm long, 2 mm wide
at the base, 0.5-0.8 mm wide at the apex, which is bluntly rounded or
slightly emarginate, straight and strongly reflexed below the ripening
fruit, showing one median nerve on the inside, margins entire; fruits
ovoid, tipped by the umbonate, persistent, very short style-base,
glabrous, gray-green, 20 X 15 mm, with 3 locules, having 1 or 2 ovules
in each locule; pulp-vesicles very rudimentary, 4-6 mm long (arising
from the dorsal ovary walls and tapering gradually to a blunt point);
peel thin (1.5-2 mm), gray-green, with numerous, slightly sunken, minute
oil glands; seeds 1 or 2, about 11 X 6 X 4 mm, monoembryonic.
This very curious plant was briefly noted
by Merrill (1926, p. 377), who published Swingle’s observations made on
a specimen of it and his own notes made shortly after its
discovery. At first sight it seemed to be allied to Atalantia
because of its unifoliolate leaves. However, it does not
have the well-developed, sessile pulp-vesicles characteristic of Atalantia but instead has rather rudimentary, corticate ones somewhat like those found in P. dubium. Then, too, its winged petioles are unlike any found in Atalantia, Severinia, or related genera, and are almost exactly like those of other species of Pleiospermium.
The long, persistent, reflexed ligulate sepals are unique in the orange
subfamily, although the evidently related species, P. latialatum, has similar sepals, persistent, cuneate, and partially reflexed, but shorter. The other three species of Pleiospermium have short sepals much like those of many other members of the subtribe Citrinae.
5. Pleiospermium latialatum Swing. Jour. Arnold Arbor. 20:261. 1939. Illus. Swingle, loc. cit. pl. 3, fig. 6.
Type.—North Borneo (Sabah), Tawao (Elmer, No. 21542). Herb. Arnold Arbor., Harv. Univ., Cambridge.
Distribution.—Known only from the original collection.
Common name.—North Borneo orangeaster.
A small tree or shrub, ultimate twigs
slender, 1-2 mm diam., at first slightly angled, soon terete, very
finely puberulent, more or less longitudinally wrinkled, nodes 1-1.8 cm
long; spines lacking (at least on fruiting branch); leaves 1-foliolate,
glabrous, shiny above, dull below, oblong-elliptical or lanceolate,
acuminate-caudate at apex, end of acumen linear for 4-6 mm and 1.5-2 mm
wide, ending abruptly with an emarginate tip, broadly rounded or very
bluntly cuneate at the base; leaf blade 9-15 X 3.7-7 cm, margins entire,
lateral veins 10-13 pairs, arising at an angle of 70°-75° with the
midrib, curving slightly toward leaf apex, oil glands small, very
numerous; petioles (all detached) short, broadly winged, obcordate,
1.6-2.4 X 1-2 cm. narrowed into a pulvinoid and minutely wrinkled terete
base, 1-2 mm long, 1.25 mm wide with a narrow channel above formed by
the decurrent wings; flowers, not seen, arising singly (?) at the tips
of short axillary branches which bear leaves or bracts below; calyx
puberulent without, sometimes persisting under young fruits, lobes
narrowly cuneate or somewhat rounded, apparently irregular in size,
acute or rounded, 2-4 mm long, 2-5 mm wide, diverging merely at right
angles to the pedicel under the young fruit; young fruits subglobose,
10-14 mm diam., glabrous, peel green, with numerous oil glands, slightly
raised above the surface with a small central depressed (crateriform);
locules 3; pulp-vesicles conical, very slender, 3-4.5 mm long, acutely
pointed, attached to the dorsal wall of the locule into which their
bases are somewhat sunken, cortication very thin with indistinct cells,
contents not degenerating to an oily or resinous mass as in P. dubium but showing axile droplets of oily substance; seeds 2 or 3, large and plump.
This remarkable species is known from a
single collection from Tawau, in North Borneo (about 175 km southwest of
Shibutu Island in Sulu Archipelago, Philippine Islands). It
is obviously related to P. longisepalum but differs strikingly
in its very broadly winged petioles, which are also relatively short,
giving them a very pronounced obcordate outline. The sepals
are sometimes (perhaps always) persistent under the developing fruit,
but are only about half as long as those of P. longisepalum and
are not completely reflexed, but stand out approximately at right angles
to the general direction of the pedicel. Only young fruits
were available for study but they show clearly that the pulp-vesicles of
this species, much like those of P. longisepalum, are very
numerous, slender-conical in shape, and slightly immersed in the dorsal
wall of the locule. The cortical layer of the pulp-vesicle
is present but not strongly developed and apparently sometimes this
cortex is so weak that the upper portion of the pulp-vesicle splits open
as the fruit develops. This species has leaves that
strikingly resemble those of Citrus in general appearance.
XVI. Burkillanthus Swing.
XVI. Burkillanthus Swing. Jour. Arnold Arbor. 20:255. 1939.
Type species.—Citrus malaccensis Ridl. = Burkillanthus malaccensis (Ridl.) Swing.; from Malacca, Malay Peninsula.
Distribution.—Malay Peninsula: Malacca; northern Sumatra: Asahan.
Common name.—Burkillanthus or Malay ghost-lime.
Leaves 3-, 2,- or 1-foliolate; leaflets
thin, with numerous strongly marked, subparallel, lateral veins;
petioles variable in length, articulated, narrowly winged or sometimes
merely margined, with pulvinoid bases; petiolules very short, pulvinoid;
inflorescences, few-flowered clusters in the leaf axils; flowers large,
5-merous with 10 stamens; pedicels short, about the length of the
styles; calyx deeply 5-lobed; petals 5, spathulate; ovary obclavate,
minutely and sparsely pubescent, merging abruptly into the much narrower
style, which is nearly as long as the ovary, with 5 locules, each with
22-26 ovules arranged in 2 rows; fruits very large, ovoid, more than
twice as long as the petioles, with a thin peel dotted with numerous oil
glands covering a thin, hard, woody endocarp; pulp-vesicles sessile
(not deeply counter-sunk) on the dorsal locule walls, very long, swollen
near the base, then cylindrical, then tapering to an acute apex,
corticate, with translucent inner core not breaking down into an oily or
resinous (?) mass; seeds very large, with a thin, slightly wrinkled
testa, immersed in mucilaginous gum and mingled with the collapsed
rudiments of the pulp-vesicles; embryo single with light buff (not
green) cotyledons.
This strange plant seems to be an
evolutionary freak of nature perhaps descended from some ancestral form
more or less like a trifoliolate Pleiospermium such as P. alatum or a uni-, di-, or trifoliolate species like P. dubium.
The pulp-vesicles of Burkillanthus are stalkless and somewhat resemble those of Pleiospermium;
however, they are very much larger and less obviously corticate, with a
central core which does not disintegrate into an oily or resinous (?)
mass resembling that of an oil gland. These pulp-vesicles of
Burkillanthus seem to represent a very interesting developmental stage about midway between the pulp-vesicles of Pleiospermium and those of Clymenia, one of the True Citrus Fruit Trees.
It is remotely possible that the curious, cavernous lining of the radial locule walls in Swinglea may, upon study of fresh material, prove to be composed of still more primitive structures analogous to the pulp-vesicles of Burkillanthus. the [sic] pistil of B. malaccensis (see fig. 3-20) is extraordinarily like that of Swinglea glutinosa in size, shape, number, and arrangement of the ovules, et cetera, except that in Swinglea the ovary is hypermerous, having 8 to 10 locules (not five as in Burkillanthus) and oil glands occur in all parts of the pistil, including the stigma (see fig. 3-20). However, the fruits of Swinglea have a very different gross structure from those of Burkillanthus and the seeds of Swinglea are not smooth but are covered with flattened laciniate paleae.
Cockrell (1935) found that the wood of B. malaccensis, as it grows near Asahan, Sumatra, is almost exactly like that of Micromelum pubescens (one
of the Very Remote Citroid Fruit Trees), differing from it only
slightly in texture and not showing any "'reasonably constant basis for
separation." However, the wood of Burkillanthus
differs decidedly from the wood of all the other genera of rutaceous
plants, 16 in all, that he studied, including eight genera of the orange
subfamily, viz.: Glycosmis, Clausena, Murraya, Merrillia, Feronia, Aegle, Atalantia, and Citrus. He did not, however, have wood of Pleiospermium or of Swinglea to compare with that of Burkillanthus.
Burkillanthus malaccensis (Ridl.) Swing. Jour. Arnold Arbor. 20:257. 1939. Citrus malaccensis Ridl. Fl. Malay Penin. 1:359. 1922. Illus. Swingle, loc. cit. pls. 2 (1/2 nat. size, not nat. size) and 3 (figs. 1, 2); figs. 3-20 and 3-21 this work.
Type.—Malay Peninsula, Malacca Territory, Nyalas (Goodenough, No. 1273). Cotype: Malacca State, Bukit Sedanan (Derry, No. 1106). Both in Herb. Bot. Gard., Singapore.
Distribution.—Malay Peninsula: Malacca; Sumatra: Asahan.
Common name.—Burkillanthus or Malay ghost-lime.
A tree up to 14 m high, some branches
with stout, straight, usually paired spines, others spineless, with
leaves mostly 1- or 2-foliolate, rarely 3-foliolate; leaflets
subcoriaceous but thin, broadly lanceolate or elliptic-lanceolate, acute
or more or less acuminate at the tips, which are blunt at the very
apex, terminal leaflets and 1-foliolate leaves variable in size, often
large, 12.5-27 X 4.5-11.5 cm, lateral leaflets much smaller, 6.5-8 X 3-4
cm, with short, pulvinoid petiolules 2-2.5 mm long, lateral nerves (of
larger leaflets) about 12-18 on each side arising at a very wide angle
(70°-85°) with the midrib, running subparallel and only slightly curved
for 2/3 or 3/4 the distance from the midrib to the margin, then
branching dichotomously, base broadly cuneate, articulated with the
petiole by means of a pulvinoid petiolule, margin subentire, very
slightly coarse-crenate; petioles of the 2- or 3-foliolate leaves 4-5 cm
long, often narrowly winged (3-6 mm in total width) at apex, narrowing
toward the base, often merely margined even at the apex; petioles of
1-foliolate leaves usually shorter, 1-3, rarely 4, cm long, sometimes
almost wingless when short; inflorescences few- (usually 1-4-) flowered,
axillary clusters, flowers large, 5-6 cm diam., borne on pedicels 5-7
mm long; calyx of 5 lanceolate-acuminate, acute sepals with large oil
glands, free nearly to the base; petals 5, subspathulate, with oil
glands in the broadened upper part, 20-25 mm long, 3.5-4.5 mm wide,
tapering into a long slender base 1-1.5 mm wide; stamens 10, filaments
free, long, slender, anthers rather small, oblong; ovary obclavate,
6.5-7 mm long, 2.5 mm diam. at the broadest part (about 2/3 the distance
from the top of the disk to the base of the style, at a point shortly
below the tips of the locules) and 1.8-2 mm diam. at the base, with 5
locales, each with 22-26 ovules in 2 rows in the upper 2/3 of the
locular cavity (see fig. 3-20),
the entire ovary covered with short sparse pubescence and with a few
small oil glands dotted over the upper half only; style slender, 5.5-6 X
0.5-0.7 mm, with small oil glands, glabrous, merging abruptly into the
tip of the ovary without any definite demarcation, swelling gradually at
the tip and surmounted by a depressed globose stigma, 1 mm high, 1.6 mm
wide, without oil glands; disk short, cylindrical, 0.6-0.7 mm high,
1.4-1.5 mm wide; fruits large, ovoid, 10-11 X 8-9 cm, outer peel thin
(2-3 mm), roughened with numerous slightly depressed oil glands, fitting
closely on woody endocarp, 2-3 mm thick, very hard in dried fruits,
that shows on its outer surface numerous slightly depressed areas 1.5-3
mm diam.; pulp-vesicles sessile, 15-33 mm long, with bases 2.5-4 mm
diam., tapering into long cylinders, 1.5-2 mm diam., which often end in
very acute tips; corticate with small tangentially compressed peripheral
cells and larger, thinner-walled central cells somewhat elongated in
their radial diameter; locules of the ripe fruit almost filled with
large seeds, apparently imbedded in mucilaginous gum, perhaps secreted
by the pulp-vesicles; seeds broadly obovate, tapering to an acute point
at the base where the seed is attached, 22-27 X 16-18 X 7-10 mm, smooth,
cream-colored, with a cinnamon brown chalazal cap covering the broad
end of the seed for 6-8 mm, monoembryonic with pale buff (not green)
cotyledons, testa thin, papery, irregularly wrinkled on dried seeds.
Burkill published (1931, p. 218) very
interesting notes on this species, as follows: "The characters of this
extremely interesting plant have not been brought into adequate
prominence. It was collected in the year 1893 twice in the
interior of the Territory of Malacca, and is represented in the
herbarium of the Botanic Gardens, Singapore, by a sheet of each
gathering. Derry obtained it with flowers in January, and
Goodenough with fruit in July. Derry's locality is given as
Bukit Sedanan; Goodenough's as Nyalas; these places are 6-8 miles
apart. Upon the two sheets there are ten leaves; and upon
each sheet one is compounded by having a single lateral
leaflet. Other leaves have a scar at the apex of the
narrowly winged petiole and therefore count as compound; others have no
scar, and obviously are simple. Trifoliate leaves do not
exist; but it would be curious if they are never produced.
There is a conspicuous joint between the petiole and the leaf-blade or
blades. The flower suggests that of Merrillia caloxylon Swingle. The sepals are in shape as those of Atalantia and
have large glands. The petals are nearly spathulate, and
with glands in the broadened upper part. The stamens
apparently are 10, free, with long filaments and rather short
anthers. The ovary is hairy and fluted with five grooves; it
is hard to distinguish the exact place where the gynophore passes into
it. The style is as long as the ovary and ends in a large
stigma. There are numerous ovules. For other
points the original description may be consulted."
This remarkable plant was first collected
in flower by R. Derry (at that time in charge of the Malacca forests)
at Bukit Sedanan, near Malacca, in January, 1893. On July 9
of the same year, J. Goodenough collected at Nyalas, only some eight
miles distant from Bukit Sedanan, a specimen with ripe or nearly ripe
fruits (see fig. 3-21) (fide
Burkill, in letter dated January 13, 1937). Thanks to the
kindness of R. E. Holttum, then director of the Botanic Gardens at
Singapore, Swingle was privileged to have the loan of the two type
specimens noted above.
E. D. Merrill directed attention in June,
1938, to a tree which he had assigned to the subfamily Aurantioideae,
collected by B. A. Krukoff (No. 4233) in November-December, 1932, in the
Nassihi Forest Reserve near Asahan in northern Sumatra (about 335 km
west-northwest of Malacca). Herbarium specimens kindly lent
by the New York Botanical Garden and the Arnold Arboretum showed that
this plant was almost identical with the type specimens of Citrus malaccensis Ridl.
The twigs of Krukoff's specimens were in part spineless but in part
armed with stiff, stout, straight, abruptly pointed, usually paired
thorns 2 to 3 cm long, and 2 to 3 mm in diameter at the
base. The leaves were uni-, di-, or
trifoliolate. A giant unifoliolate leaf in the New York
Botanical Garden herbarium had a petiole 2 cm long and a broadly
lanceolate blade, 27 by 11.5 cm, short-acuminate at the apex, cuneate at
the base. It had 17 or 18 principal lateral veins, and
about 9 or 10 shorter laterals, arising at angles of 70° to 80° with the
midrib (see Swingle, 1939a, p. 262, pl. 2). The
ovoid fruit measured about 11 cm long and 9 cm wide. The
inner side of the dorsal walls of the locules were thickly covered with
cylindrical or subclavate (?) saclike pulp-vesicles, as described
above. No similar pulp-vesicles are known in any other genus
of citrus fruit yet studied.
In a letter to Swingle, dated April 19,
1940, R. E. Holttum reported that a collector whom he had sent to Bukit
Sedanan, the type locality of B. malaccensis, found this species
growing there in quantity "in primitive forest, but only on the ridges,
where the shade is less than on the valley slopes." The
trees were about 30 feet (9.15 m) high and bore half-grown fruits.
In June, 1941, a large fruit, slightly
over 10 by 16 cm, was sent to Swingle by air express from the Singapore
Botanic Gardens. It reached Washington in good condition,
which made it possible to study fully developed pulp-vesicles in the
living state. This fruit contained more than 120 very large,
mature seeds. (See fig. 3-21.)
This remarkable tree should be studied in
the living state and possibly tested as a rootstock for Citrus. It is called by the Malays limnan hantu ("ghost lime"), a name also applied to wild forms of Citrus according to Burkill (1931, p. 221), perhaps because its large fruits are not unlike those of some species of Citrus in size and shape.
XVII. Limnocitrus Swing.
XVII. Limnocitrus Swing. Jour. Arnold Arbor. 21:2. 1940.
Type species.—Paramignya ? littoralis Miq. = Limnocitrus littoralis (Miq.) Swing.
Distribution.—Java: Bali; South Vietnam.
Common name.—Limnocitrus or swamp-orange.
A shrub with glabrous twigs having stout,
axillary, single spines at the nodes; leaves simple, coriaceous,
glabrous, broad-elliptical or obovate, bluntly pointed at the tip and
broadly cuneate at the base; petioles short (less than 1/10 as long as
the leaf blade), pulvinoid, not articulated with the leaf blade;
inflorescences terminal, short, corymbose; flowers 4- or 5-merous, borne
on very short, glabrous pedicels; flower buds oblong, greenish; calyx
4-5-lobed, lobes triangular, obtuse; petals linear-lanceolate, obtuse,
white; stamens 10, filaments free, glabrous, anthers linear; disk
annular; ovary oblong-ovate, with 15-20 narrow hirsute ridges, with a
single large oil gland over each of the 4 or 5 locules, each having 2
ovules; style slender, sparingly hirsute, stigma slightly capitate,
distended with large oil glands between the stylar canals; fruit globose
or subglobose, rather large (3.5-4 cm diam.), with a gland-dotted peel,
becoming orange-colored when ripe, filled with very numerous, slender,
fusiform pulp-vesicles, slender and acutely pointed at tip and abruptly
truncate at the broad base about 1/3-2/3 as wide as the broadest part,
which is near the base, with a slender axile [sic] column of
whitish granules (oil or resin drops?) in the center; seeds large,
flattened-oval, with a hard, creamy-white testa, monoembryonic, embroyo
green, cotyledons dotted with oil glands.
This remarkable plant has been placed in
several different genera by the few botanists who have discussed
it. It has certain resemblances to the species of Pleiospermium
but differs from them in several important characters: (1) in having
simple leaves with very short pulvinoid petioles; (2) in having slender,
fusiform pulp-vesicles with very slender, acute tips and slightly
narrowed at the base where attached; (3) in having thick, sparingly
veiny leaves; (4) in having straight, very stout, single spines in the
leaf axils.
Limnocitrus is distinguished from Atalantia
by its very slender-tipped pulp-vesicles, which are not conical and do
not have broad bases deeply immersed in the locule wall, as in Atalantia,
but are fusiform and narrowed into a definite, though very short, basal
stipe. The leaves are thicker and differently veined and
the whole plant has a different facies from that of Atalantia.
In many ways the pulp-vesicles of Limnocitrus are intermediate between those of the True Citrus Fruit Trees (Citrus and the five most closely related genera) and those of the Near-Citrus Fruit Trees (Citropsis and Atalantia) and some of the Primitive Citrus Fruit Trees, especially Pleiospermium. In most of its other characters, Limnocitrus
stands very much alone. The leaves are different in
texture, venation, and general appearance from those of all the other
twelve genera in the subtribe Citrinae. However, similar,
although not identical, leaf and twig characters are found in Merope and Pamburus, two monotypic genera of the Minor Citroid Fruit Trees, subtribe Triphasiinae, which also grow in brackish marshes.
Limnocitrus littoralis (Miq.) Swing. Jour. Arnold Arbor. 21:3. 1940. Paramignya ? littoralis Miq. Ann. Mus. Bot. Lugd.-Bat., 1:211. 1863, and Teijsmann & Binnendijk, Natuur. Tijdschr. Nederl.-Indie 27:41. 1864; Limonia littoralis (Miq.) Backer, 1911; Atalantia littoralis (Miq.) Guill. 1913; Pleiospermium littoralis (Miq.) Tan. Bul. Mus. Hist. Nat. Paris, 2 ser. 2:162. 1930. Illus. Valeton, Icon. Bogor. 4:163, pl. 349. 1912; Swingle, loc. cit. pl. 1; fig. 3-22 this work.
Type.—Java, Rembang, on seashore (Teijsmann). Rijks. Herb., Leiden.
Distribution.—Java: Bali; South Vietnam: Annam, Cochin China.
Common name.—Limnocitrus or swamp-orange.
This species was based on a specimen
collected by Teijsmann on the seashore at Rembang on the north coast of
Java. Miquel's original description reads, in translation,
as follows: "Spines solitary, straight, arising nearly at right angles
to the twig; leaves simple, with very short petioles, acute or acutish
at the base, broad- or obovate-elliptical, apex obtuse or somewhat
protracted-obtuse and emarginate, coriaceous, pellucid-punctate,
reticulate, venose below, [margins] very slightly crenulate; leaves 2-3
in. [5-7.6 cm] long; flowers in terminal tufts, forming much contracted
cymes, with very short, thick pedicels; calyx unequally 5-toothed;
petals 5, elliptic-oblong, imbricate; stamens 8, filaments very short,
anthers linear, marked with an oblong gland on the back, joined together
in the bud; ovary inserted on a short disk, 5-angled, sparsely pilose, 5
locular, ovules 2 in each locule, subcollateral; style thick, stigma
slightly capitate, obscurely 5-lobed; fruits globose, 2- or 3-seeded,
about the size of apricots, with distinct, empty locules."
Another description published almost
simultaneously by Teijsmann and Binnendijk (doubtless based in part on
independent observations of the species by Teijsmann, who discovered it
at Rembang) supplements Miquel's original description.
Omitting obvious duplications, this reads, in translation, as follows:
"Branches cinereous, twigs very glabrous; spines 1/2 in. [12.5 mm] long,
stout; leaves emarginate at the apex, rarely obtuse; racemes [sic]
short, sessile…calyx 4-5-lobed; filaments 10, free; ovary pubescent,
4-5-locular, ovules paired; fruits baccate, very fetid, 2.3 cm diam.,
locules by abortion 1-seeded."
In the notes following the technical
description they add, regarding the fruit, that it is
"depressed-globose, about the size of a lime, becoming
orange-colored…4-5-locular…pulpy; rind, leathery-glandular.
Seeds large, testa membranaceous, white. Cotyledons fleshy,
plano-convex, green."
One of the most important characters of
the species, overlooked by Miquel but brought to light by Teijsmann and
Binnendijk, is that the locules of the fruit contain pulp.
This was mentioned a few years later by Kurz, who lived for some years
in Java, where he doubtless saw Teijsmann's specimens collected at
Rembang. Kurz wrote (1875, p. 136, footnote): "The berries
of P[aramignya] littoralis Miq., a species closely allied to P. angulata [= Merope angulata], have pulp, but the dried ones appear pulpless."
Fortunately Swingle was able to
supplement the above-quoted descriptions and a later one by Valeton
(l.c., p. 163), all based on a single collection made at Rembang, Java,
from excellent material from Indo-China. Flowering specimens
studied were from plants growing in a hedgerow near houses at Tourane,
Annam (coll. by J. and M. S. Clemens, No. 3263), in Herb. Arnold
Arboretum; fruiting material was from Nhatrang, Annam (Aug. Chevalier,
No. 30526, February 6, 1916), in Herb. National Arboretum.
This material showed the following characters:
A shrub or small tree 2 m high with
stout, straight, single spines; leaves simple, glabrous, broadly oval,
bluntly pointed at both ends, margins entire or faintly crenulate; leaf
blades 5-7.5 X 3-4 cm, with 8-11 pairs of lateral veins, arising at
angles of 40°-60° with the midrib, usually straight but sometimes
bending to the right or left to unite with the neighboring lateral vein,
tertiary or quaternary veinlets forming coarse, irregular,
inconspicuous reticulations, oil glands small, very numerous; petioles
cylindrical, 3.5-7 X 1-1.5 mm, pulvinoid, minutely puberulous on the
upper side inside the shallow channel bounded by the decurrent leaf
margins; inflorescences terminal (sometimes also small ones in axils of
last few leaves), corymbose, 3-4 X 2.5-5 cm, pubescent, peduncles
abundantly and divaricately branched, divided into nodes (5-10 X 1.5-2
mm) by thick, blunt-pointed, pubescent, caducous bracts, 1-5 X 0.8 mm,
pedicels 2.5-3.5 mm long, expanding gradually into the base of the calyx
without any articulation; calyx glabrous without, 4-5-lobed, lobes
bluntly pointed, finely pubescent within, with short-ciliate margins;
petals white within, green without in the bud and greenish-white when
expanded, linear-oblong, blunt-tipped, 10-11 X 3 mm, glabrous except for
scattered puberulence near the tip; stamens with glabrous filaments,
anthers long and slender, 4.5 X 1 mm, with a large dorsal oil gland;
disk cup-shaped, 0.5-0.6 mm high, 1.5-1.6 mm wide, enclosing loosely the
base of the ovary for 0.2-0.25 mm; pistil 10-11 mm long; ovary obovoid,
4.5-5 mm high, 1.7-2 mm wide, flattened at top, obscurely ribbed in
middle portion with 15-20 slight ridges from which arise scattered long
hairs, pentagonal at the top because of large sunken oil glands (1 over
each locule), locule [sic] 4-5, each with 2 pendant collateral
ovules; style 6 mm long, 1.8-2 mm thick, terete, sparingly pilose above,
increasingly so toward the base, stigma depressed capitate, 1.8-2 mm
wide, 0.7-0.8 mm high, with 4-5 radially arranged, linear stylar canals,
with 2 (rarely 1) large oil glands between each adjoining pair of
stylar canals; fruits subglobose, 37-40 mm diam., peel thin, dotted with
oil glands, containing numerous, very slender, fusiform pulp-vesicles,
9-11 mm long, gradually tapering to 0.5-0.8 mm diam. at the base where
attached to dorsal wall of locule, the broadest portion (1.6-1.8 mm) of
the pulp-vesicle is situated about 1/10-1/6 of the distance from the
base to the tip, the slender apical portions often matted and tangled in
dried specimens; seeds long obovate, 17-18 X 9-11 X 3.5 mm, with a
smooth, firm, yellowish-gray testa, monoembryonic; cotyledons green,
gland-dotted.
This little-known species apparently has a
fairly wide distribution, as it has been found in Annam and Cochin
China in South Vietnam, as well as in Java and Bali.
However, it has been collected only a few times since it was discovered
by Teijsmann some seventy-five years ago at Rembang in Java, where
apparently it has not been seen since.
It has, however, been collected several times near Nhatrang in Annam (see fig. 3-22),
and once at Tourane. It grows in tidal swamps subject to
overflow with brackish water at spring tides. Guillaumin
(1913, p. 442), in describing the plant as found in the vicinity of
Nhatrang, wrote: "The fruits, as a matter of fact, resemble small
oranges about 4 cm in diameter, with five locules almost completely
occupied by two very large seeds surrounded by pulp formed by succulent
hairs, as in the genus Citrus and in Atalantia citroides." He went on to say that it is called kim-do-um by the natives at Nhatrang and that, since it grows on sea beaches, it is probably salt-resistant.
Limnocitrus, from its habitat, is almost certain to possess a high tolerance to salinity in the soil moisture. Citrus can be grafted on Merope, but has made only unsatisfactory growth. It is probable that Citrus would grow better when grafted on Limnocitrus, to which it is much more closely related than to Merope (a member of another subtribe). Such a rootstock might be expected to be useful wherever Citrus is grown in soils showing a high salinity in the soil moisture, as has been found to be true with the xerophytic Eremocitrus, native to more or less saline flats in the semiarid plains of Australia.
XVIII. Hesperethusa Roem.
XVIII. Hesperethusa Roem. Syn. Hesper. 1:31. 1846. Limonia Sec. III, Hesperethusa Engl. Die Nat. Pflanzenfam. 3(4):190. 1896.
Type species (monotype.—Limonia crenulata Roxb. = Hesperethusa crenulata (Roxb.) Roem.; from British India.
Distribution.—Northern India, Burma, southwestern China, Thailand, South Vietnam, Laos, Cambodia.
Common name.—Hesperethusa.
Slender, thorny trees or shrubs; leaves
persistent, odd-pinnate; petioles and rachis broadly winged (petioles
sometimes more narrowly winged); inflorescences axillary, few-flowered;
flowers small, 4-merous (except stamens, twice as many as petals); ovary
with 4 locules, 1 ovule in each locule; fruits small, 1 or more of the 4
segments with a single seed, surrounded by scanty, bitterish pulp
containing large rudimentary sessile pulp-vesicles of irregular size and
shape; seeds hard, smooth, germinating with epigeous cotyledons.
Hesperethusa has apparently no near relatives, differing widely from all the other genera of the Citrus Fruit Trees except Citropsis
in having odd-pinnate leaves with three to four pairs of small,
opposite, crenate leaflets and broadly winged petioles and rachis
segments. Pinnate leaves were undoubtedly borne by the
remote ancestors of all the Citrus and Citroid Fruit Trees (the tribe
Citreae). The characters persist today only in two out of
the thirteen genera (Hesperethusa and Citropsis)of the second subtribe, Citrinae, and in two out of the seven genera (Feronia and Feroniella)
of the third subtribe, Balsamocitrinae. None of the eight
genera in the first subtribe, Triphasiinae, have pinnate
leaves. In other words, only two of the three subtribes of
the tribe Citreae have genera with pinnate leaves, and out of a total of
twenty-eight genera in the tribe only four have pinnate leaves.
Hesperethusa has some other points of similarity with the African genus Citropsis aside
from pinnate leaves. The seeds of both genera have a hard
testa, cream-yellow in color, composed of radial prismatic cells, some
with very thick walls. The little known Citropsis daweana from Portuguese East Africa has the smallest leaflets of any of the species of Citropsis,
with widely winged rachis segments but nearly wingless petioles, making
the leaves look somewhat like those of certain forms of Hesperethusa crenulata.
The very small fruits of this monotypic
genus show rudimentary pulp-vesicles attached to the dorsal wall and
apparently also to the base of the locule. There are
relatively few of these pulp-vesicles in each locule of the developing
fruit; they are not clearly differentiated into basal and apical
portions but are irregularly rounded and seem to be thin-walled; they
vary greatly in size, and are often polygonal from mutual
pressure. These rudimentary pulp-vesicles can be seen in the
sections12
of the fruits of paratypic material in the Kew Herbarium which was
collected by Roxburgh in the last quarter of the eighteenth century and
from which he drew up the description of Limonia crenulata, the type species of the genus.
The pulp-vesicles of Hesperethusa that
arise from the dorsal wall of the locule appear like small vesicles
adhering to the wall by a broad base and are broader than
high. The few pulp-vesicles that arise from the base of the
locule are more or less slender and elongated but do not have any
clearly marked stalk. The shapes taken by the pulp-vesicles
seem to be governed by the free space available into which they can
expand as they develop. The pulp-vesicles attached to the
dorsal wall are somewhat like those of Pleiospermium in shape but
they do not show any definite cortical layer and furthermore do not
show any degenerations of the central portion into an oily or resinous
(?) mass.
Hesperethusa can be grafted on Citrus and such grafts live and grow for many years.
Dr. Anna E. Jenkins (1936, pp. 71, 73) discovered on the fruits of Hesperethusa from India a fungus, Elsinoë sp., very like the scab fungi, E. fawcettii and E. australis, that attack species of Citrus.
Hesperethusa crenulata (Roxb.) Roem. Syn. Hesper. 1:38. 1846. Limonia crenulata Roxb. Pl. Corom. 1795; L. acidissima Auct. (non L.). Illus. Rheede & Draakestein, Hort. Malabar. 4:31, pl. 14. 1679; Roxburgh, loc. cit. 1:pl. 86; Talbot, Forest Fl. Bomb. Presid. 198, fig. 121. 1909; Engler, Die Nat. Pflanzenfam. 3(4):190, figs. J, K, L. 1896; Swingle, in Bailey, Stand. Cycl. Hort. 3:1478, fig. 1825. 1915; fig. 3-23 this work.
Type.—Peninsular British India (Roxburgh). Herb. Brit. Mus., London (fide Tanaka).
Distribution.—West Pakistan, India, Burma, Thailand, southwestern China, South Vietnam, Laos, Cambodia.
Common name.—Hesperethusa.
Talbot (1909, pp. 198, 199) described
this species as follows: "A spinous, glabrous, small tree: spines
straight 0.5"-1" [12-25 mm] long. Leaves imparipinnate;
leaflets 2-3 pairs, 1"-2" [2.5-5.1 cm] by 0.5"-1" [1.2-2.5 cm],
conspicuously gland-dotted, sessile, ovate, emarginate, crenulate;
terminal leaflet usually largest; rachis and petiole broadly winged,
jointed; joints of rachis obovate. Racemes short, axillary,
pubescent, subumbellate, few-flowered. Flowers
4-merous. Calyx small, glandular, 4-lobed; lobes
ovate. Petals 4, fragrant, white, 0.25" [6 mm] long,
elliptic. Disk annular or stipitate. Ovary
4-celled with 1 pendulous ovule in each cell; style short.
Fruit globose, 1-4 seeded, 0.25" [6 mm] in diameter, black when ripe;
pedicels 0.75" [19 mm] long."
Hesperethusa has a wide range from
West Pakistan to Burma, southwestern China on to southern Indo-China
(Cambodia). In West Pakistan and India, it occurs commonly
in the sub-Himalayan tract from Ravi River (Long. 75° 30' E.) eastward,
ascending to 4,000 feet [1,220 m] altitude.
This species is a small tree reaching a
height of 25 to 30 feet (7.6 to 9.14 m); it grows commonly on dry hills
or in dry jungles. It was said by Haines (1921, vol. 2, p.
163) to be "subdeciduous at the time of flowering." The wood
is largely used in Bihar and Orissa, India, for cart axles.
Several authors have stated that the spines are sometimes paired and
that the leaves often have four pairs of leaflets. The
inflorescences often bear from one to several foliage leaves at the
base, and leaf spurs (Kurztrieben), with very short internodes,
are often borne in the axils of the leaves of older twigs.
The petioles of the leaves on such Kurztrieben are often more
narrowly winged than the rachis segments of the same leaves and are
sometimes almost wingless. The fruits are said by many
authors to be very acid, but Haines (1921, vol. 2, p. 163) reported them
to be "intensely bitter (not acid)."13
Guillaumin (1911, p. 660) spoke of the seeds being "immersed in a
mucilage," but no one seems to have realized up to now that the locules
of the fruit contain rudimentary pulp-vesicles. Hesperethusa crenulata produces
a hard, close-grained, light yellow wood in India, and its leaves,
fruits, and roots are used in making medicine in that
country. According to Watt (1890, vol. 4, p. 642) the fruit
is exported from India "to the Arabian coasts, where it is used as a
condiment with fish, meat, etc., being powdered along with the spices
commonly used in cooking."
Hesperethusa crenulata is promising as an ornamental because of its beautiful, feathery, green foliage (see fig. 3-23). Grafts of it on Citrus
were still growing in the greenhouses of the Agricultural Research
Service at Washington after 20 years, although the union of the stock
and scion was somewhat swollen. It can also be grafted on Swinglea glutinosa (the Philippine tabog), which belongs to the subtribe Balsamocitrinae.
Group B. THE NEAR-CITRUS FRUIT TREES
This group includes two genera, Citropsis and Atalantia, that show well-developed pulp-vesicles having broad sessile bases and conical sides that taper regularly to the acute apices.14
These pulp-vesicles are arranged more or less radially with the bases
at the periphery of the fruit locules attached to the dorsal walls of
the locules and imbedded in the inner layer of the rind. The
conical pulp-vesicles usually point toward the center of the fruit
unless deflected by the seeds, which (if present) are attached at the
inner angle of each locule. The genus Citropsis,
native to tropical and subtropical Africa, has eleven species, all but
one with pinnate or trifoliolate leaves resembling in several important
characters those of the genus Hesperethusa of group A; Atalantia,
native to southeastern Asia (including Ceylon), likewise has eleven
species, but all have unifoliolate or simple leaves much resembling
those of Citrus of group C in size and shape but differing in their more leathery texture and finer venation.
Both Citropsis and Atalantia are obviously related to the True Citrus Fruit Trees of group C, and some three species of Citropsis and two or three special of Atalantia (all that have been tested) can be grafted on Citrus,
and vice versa. These two genera are intermediate in
character between the Primitive Citrus Fruit Trees of group A and the
True Citrus Fruit Trees of group C; like the genera in group A they
contain many obvious connecting links between Citrus and the Minor Citroid Fruit Trees of the subtribe Triphasiinae.
XIX. Citropsis (Engl.) Swing. & M. Kell.
XIX. Citropsis (Engl.) Swing. & M. Kell. Jour. Agr. Res. 1:421. 1914. Limonia Sec. citropsis Engler, Die Nat. Pflanzenfam. 3(4):189. 1896.
Type species.—Limonia preussi Engl. (from Elephant Lake, Cameroons) = Citropsis articulata (Willd.) Swing. & M. Kell. (ranging from Togo to Cameroons and to Belgian Congo).
Distribution.—Not uncommon from Uganda to Nigeria and Sierra Leone, and south to Republic of the Congo, Angola, and Mozambique.
Common name.—African cherry-oranges.
A genus of Near-Citrus Fruit Trees found
in tropical Africa. Shrubs or small trees with 1 or 2
well-developed spines (C. angolensis is said to be spineless) in the axils of the leaves; leaves pinnate, sometimes 3-foliate [sic], rarely 1-foliolate (simple in C. tanakae); rachis and petiole usually broadly winged (wingless in C. le-testui),
flowers 4- or 5-merous, usually in dense axillary clusters or short
racemes; stamens twice as many as the petals, filaments free, flattened
laterally and in some species cohering laterally at the base in groups;
ovary with 4 or 5 locules, each with a single ovule; fruit spherical,
small (2-3 cm diam.), with pulp-vesicles broad at the base where they
are attached and tapering to an acute tip; seeds large (10 X 6 X 4 mm);
cotyledons hypogeous in germination.
This genus is certainly closely related to Citrus, in spite of the fact that all but one species of Citropsis have pinnate or trifoliolate leaves. It belongs, along with Atalantia,
to group B, the Near-Citrus Fruit Trees, of the subtribe
Citrinae. Both of these genera have small, subglobose
fruits, 1.5 to 3 cm in diameter, with 3 to 5 locules, in which occur
broad-based, sessile, conical, radially arranged
pulp-vesicles. All the species of Citropsis have leaves, or leaflets, very similar to those of Citrus in shape, venation, and texture, whereas the leaves of the species of Atalantia are thick, more leathery, and much more veiny than those of Citrus.
The seeds of Citropsis are plump
and broadly ovoid with a very hard, smooth testa. The hilum
is an oval or ovate aperture bordered by the incurved testa, which is
here very hard and thick. No other genus of the subtribe
Citrinae has seeds as plump and as hard-shelled. The flowers
of Citropsis differ greatly in the various species with respect
to size and proportion of parts, and especially with respect to the
morphology of the pistil. The leaves differ even more than
the flowers in the different species, but fortunately for the taxonomist
the leaf and flower characters are not closely correlated; that is, a
pair of species having very similar leaves, like C. schweinfurthii and C. angolensis, may show easily recognized differences in the flowers. Citropsis schweinfurthii and C. gilletiana have similar flowers, with only slight differences in the pistil, but very different leaves.
The species of Citropsis look like missing links, i.e., surviving forms of the remote ancestors of Citrus
and may, in fact, be such forms that migrated tens of millions of years
ago from the southeastern Asiatic homeland of the tribe Citreae and
found safe and congenial refuge in the tropical forests of Africa, where
they have persisted with little change ever since. Once
safely in Africa, the ancestors of Citropsis were freed from
competition with the numerous species of related genera of the subtribe
Triphasiinae as well as from the danger of hybridization with vigorous
new genera that evidently arose in rapid succession in southeastern Asia
and the East Indian Archipelago. Thanks to this age-long
isolation, even today the leaflets of Citropsis (and especially the unifoliolate leaves of certain forms of C. gabunensis) resemble very closely the leaves of Citrus (and doubtless those of the common ancestor of Citrus and Citropsis)
in shape, texture, venation, and color. That this
resemblance of the leaves is no mere analogy is proved by the fact that
the species of Citropsis, so far as they have been tested, graft readily on Citrus, and vice versa. Citropsis and Pleiospermium are the two genera that most nearly represent today the remote ancestors of Citrus.
The species of Citropsis are all
native to tropical and subtropical Africa, from Sierra Leone to Angola
on the west coast and from Uganda south to Mozambique in East Africa, as
well as to many, if not all, of the regions of central Africa lying
between. As this immense territory includes vast areas still
only inadequately explored, it is highly probable that several, perhaps
many, more species of Citropsis will be discovered in the future.
A striking proof of the inadequacy of our
botanical exploration of tropical Africa is shown by the fact that, of
the eleven species of Citropsis here recognized, eight were discovered after 1900 and five of these after 1920. The last three species to be found—C. gilletiana, C. tanakae,and C. daweana—were
described as recently as 1940! The two last-named are
strikingly different from all the other known species and from each
other. They are not mere small species made by splitting
large species, but are new and aberrant members of the genus, which when
better known may need to have new subgenera made to include
them. One subgenus, Afrocitrus, has already been named to include three allied species, all growing in western tropical Africa.
In the Congo, it was found that Gillet’s cherry-orange, C. gilletiana,
the most vigorous species in the genus, growing to be a tree 10 meters
high, could be used to advantage as a rootstock for cultivated varieties
of Citrus because of its resistance to foot rot (very injurious to cultivated varieties of Citrus
there). This species proved to be an even better rootstock
than the sour orange for the orange, the mandarin, the pummelo, and the
lemon (see below). It is one of the more important rootstocks for Citrus found in this century.
In view of the beauty of their foliage,
the refreshing fragrance of their flowers, and the attractive aroma of
their tiny fruits, coupled with their rapid growth and free flowering
while still small trees, an effort should be made to test all the
species of Citropsis as greenhouse ornamentals in the cooler climates and as out-of-door ornamentals in subtropical regions. Keys to the subgenera and species of Citropsis are presented.
Subgenus Citropsis
Subgenus Eucitropsis Swing. & M. Kell. Jour. Arnold Arbor. 21:125. 1940.
Type.—C. Schweinfurthii.
Leaflets usually large, petioles and
rachis segments broadly winged; ovary ovoid without a single large oil
gland at the top of each locule; stigma medium-sized, depressed-globose,
without large oil glands; staminal filaments glabrous.
Most of the species of this subgenus have large leaves, and three of them, C. articulate, C. gilletiana, and C. latialata,
have leaves and leaflets larger than those of any other members of the
tribe Citreae except possibly the palmately trifoliolate leaves of
certain species of Luvunga. The species of this subgenus are rather sharply distinguished from those of the subgenus Afrocitrus by the ovary and stigma characters.
1. Citropsis schweinfurthii (Engl.) Swing. & M. Kell. Jour. Agr. Res. 1:426. 1914. Limonia schweinfurthii Engl. Notitzbl. Bot. Gart. Berlin 1:28. 1895. Illus. Swingle & M. Kellerman, loc. cit. figs. 1-2, 4(C)-7, pl. 49; Swingle, in Bailey, Stand. Cycl. Hort. 2:780, fig. 972. 1914; Engler, Die Nat. Pflanzenfam. 19a:348, fig. 158,K (copy of fig. 4,C above). 1931; fig. 3-24 this work.
Type.—Uando, northwestern Uganda (Schweinfurthii, No. 3656, 1870). Herb. Bot. Mus., Berlin-Dahlem.
Distribution.—Northeastern tropical Africa, northwestern Uganda, and northeastern Republic of the Congo, at altitudes of 600-1,600 m.
Common name.—Uganda cherry-orange.
Small tree, ultimate branches at first
angled, soon terete, often with single or paired spines 1-2.5 cm long;
leaves medium-sized, 3-5-foliolate, 12-30 X 12-20 cm, leaflets oblong or
lanceolate, tapering rather abruptly to a short, blunt acumen, cuneate
at base, margins denticulate to subentire, terminal leaflets usually
narrowly cuneate at base, 10-15.5 X 3-5.5 cm, lateral leaflets more
broadly cuneate at base, 8-14 X 3.5-5.5 cm, petioles broadly winged but
usually slowly narrowed and rounded at both ends, 5.5-10 X 2-3 cm,
rachis segment similar in shape to petioles but shorter and narrower,
4-9 X 1.5-2.8 cm; inflorescences axillary, short (1-2 cm), many
flowered, pedicels 2 mm long, 1 mm wide at base, gradually thicker
upward and about 2 mm wide at base of calyx, flowers white, fragrant,
usually 4-merous, about 2.2-2.5 cm when fully expanded, calyx with 4
thick, short, blunt lobes, petals 4, 12-15 X 4-5 mm, broadly rounded at
tips, stamens 8, 10-11 mm long, flattened and broad 3/4 of way to top,
0.5 mm thick, 1.4-1.6 mm broad; disk 1 mm high, 3 mm broad, surrounding
narrowed base of ovary with a shallow (0.3-0.4 mm), thick-walled cup
with small scattered oil glands on inside near base, pistil 10-11 mm
long (including disk), ovary ovate, 4-locular, 2 mm high, 2.5 mm wide,
rounded at tip with style often (always ?) attached to one side of
center of tip!, style short, stout, 6-7 X 1.1-1.4 mm, expanded slightly
at tip, stigma cushion-shaped, 0.9-1.1 mm high, 2-2.5 mm wide, 4-lobed
at tip, with very small oil glands between stylar canals; fruits
subglobose, lemon-yellow when ripe, fragrant, 2-2.2 cm diam., locules
filled with numerous, sessile pulp-vesicles that occupy all free space,
seeds slightly roughened, 9-12 X 7-8 mm, monoembryonic.
Citropsis schweinfurthii was grown
for many years in the United States and thrived in the Washington
greenhouses of the U.S. Department of Agriculture, where it flowered
profusely and set fruit freely while still a small tree. The
leaflets are narrower than those of most of the other species except
the related C. angolensis of Angola and the very different C. daweana
of Mozambique. The leaflets of the Uganda cherry-orange
show 6 to 8 lateral veins, slightly elevated below and slightly
depressed above. The surface of the leaflets is nearly
plane. The fruits of C. schweinfurthii are often
borne in clusters of two to five on short axillary inflorescences; they
are almost spherical or very slightly flattened at the top and 22 to 25
mm in diameter. The peel is very thin, 1 to 1.5 mm
thick. The ripe fruit ranges in color from Empire yellow to
Apricot yellow (Ridgway, 1912, pl. 4). The pulp, when seen
in cross section, is straw yellow, amber yellow, or even mustard yellow
(Ridgway, 1912, pl. 16) near the peel. The pulp-vesicles
fill all the space in the cells of the ovary not occupied by the plump
seeds, of which 1 to 4 may develop, never more than one in each
locule. The pulp-vesicles contain in their center a long
column of oil droplets, irregular in diameter and not sharply
delimited. The oil droplets are extremely variable in size,
though most of them are small. The mawkish taste of the pulp
is doubtless due to these droplets of oil.
The Uganda cherry-orange can be grafted readily on Citrus
(Swingle and M. Kellerman, 1914, p. 435, pl. 49). It can
also be made to grow, but less vigorously, when grafted on the wood
apple, Feronia limonia, or on the Philippine tabog, Swinglea glutinosa. It
is well worth growing as an ornamental in the greenhouse, as it not
only has handsome foliage, but also bears, for months at a time, a great
profusion of white bloom looking much like orange flowers, with a
strong but agreeable odor about midway between that of citrus flowers
and that of the North American wild plums (Prunus americana and other species).
2. Citropsis angolensis Exell, Jour. Bot., Brit. & For. 65(Suppl. 1):53.
Type.—Angola, Amboine
(Grossweiler, No. 4454). Herb. Brit. Mus.
Fragments and serial microtome sections, S. and T. Nos. 273-A, 273-B,
and 273-C, 12 slides, in Herb. Natl. Arbor., Washington, D.C.
Distribution.—Known with certainty only from the type locality.
Common name.—Angola cherry-orange.
The original description by Exell reads
as follows: "A tree with brown branchlets; leaves trifoliolate, leaflets
elliptical or obovate, cuneate at base, margins remotely and
irregularly crenate, glabrous on both surfaces, petioles broadly winged,
elliptical; flowers pedicellate, pedicels glabrous, in clusters in the
axils of the leaves; sepals 4, triangular, small; petals 4, oblong,
imbricate, rounded at the tips; stamens 10, filaments free, flattened,
glabrous; ovary 4-locular, style scarcely thickened at the base.
"A tree, total height 15 feet [4.6 m];
shortly branched from the base. Leaflets 8-12 X 4-6 cm;
petiole 7-8 X 2.5-3 cm; pedicels 5-7 mm long; petals 12-14 X 5-6 mm;
filaments of stamens 8-9 mm long; anthers 4 mm long affixed near the
base; ovary 4 mm long and 2.5 mm in diam., style 6 mm long; young fruits
8 X 5 mm.
"The species is nearest to C. Schweinfurthii
(Engl.) Swing. and M. Kell., but has rather longer pedicels and a
slightly longer and slenderer style—it is, moreover, apparently devoid
of spines."
The two flowers from the type specimen
were kindly donated to Swingle by the Curator of the Herbarium of the
British Museum. A nearly mature flower bud was cut into
several hundred serial microtome sections (both cross and longitudinal)
and a fully mature flower from which the petals and stamens had just
fallen was restored to natural state and photographed. The
following characters were observed:
Pistil slender, 1.2 cm long, with a very
slender style, 6 mm long, borne on a slender pedicel, 0.7 mm diam. at
base and 1 mm diam. at top; calyx very small (2.3 mm diam.), lobes
triangular, acute, with several (2 or 3) small oil glands near the tip;
stamens free, filaments flattened, anthers 3-3.5 mm long, apparently
without an oil gland near the tip; disk small, 1 mm high, 1.3-1.5 mm
wide, and nearly cylindrical on mature, dry flowers, but bulging to 1.8
mm at mid-height in nearly mature flower buds (and on a restored mature
pistil), not cupulate and not enclosing the ovary base; ovary
truncate-fusiform (ellipsoid), 3.5(-4 ?) mm high, 1.3 mm wide at base,
1.8 mm wide in middle in dry flowers (2-2.5 mm wide on a fully restored
mature pistil), 4-locular, narrowed at tip and merging gradually into
style base; style slender, 6 mm long, 0.8-1.3 mm wide, expanded rather
abruptly into the subglobose stigma which is 1.1 mm high, 1.6 mm wide
when dry (1.2 mm high, 2 mm wide in restored mature pistil), with 1 or 2
small oil glands between the stylar canals.
The flower characters of this species
show clearly that, in spite of the general resemblance of its leaves to
those of C. schweinfurthii, it is in fact a very distinct
species, differing decidedly in its spineless twigs, in its longer ovary
and its longer, more slender style arising from the center of the top
of the ovary (not from one side as in C. schweinfurthii), and,
even more strikingly, in its very different, noncupulate disk, which
does not enclose the base of the ovary even to the slightest extent.
This species of Citropsis can, as a matter of fact, be distinguished only with difficulty from C. schweinfurthii by
any of the easily visible, grosser characters of the leaves, flowers,
or fruits and has in fact been considered by experienced taxonomists to
be a mere synonym of it, not even worthy of being distinguished as a
variety. At first glance the only distinguishing character
is the absence of spines in C. angolensis and their abundance in C. schweinfurthii. However,
when the flowers are studied critically, striking differences appear
which not only separate clearly the Angola cherry-orange from the Uganda
species but also distinguish it from all the other known species of the
genus Citropsis.
3. Citropsis articulata (Willd.) Swing. & M. Kell. Jour. Agr. Res. 1:433. 1914. Citrus articulata Willd. in Spreng., Syst. Veg. 3:334. 1826; Limonia preussii Engl. Notitzbl. Bot. Gart. Berlin 1:28. 1895; Citropsis preussii (Engl.) Swing. & M. Kell. Jour. Agr. Res. 1:423. 1914. Illus. Swingle & M. Kellerman, loc. cit. p. 424, fig. 3; p. 425, fig. 4,A; Engler, Die Nat. Pflanzenfam. 19a:348, fig. 158,F,G,H. 1931.
Type.—In the mountains 50-75 km north of Accra (Isert. 1786). Herb. Bot. Mus., Berlin-Dahlem.
Distribution.—Ghana, Togo,
Cameroon, Republic of Congo (?). This species widely spread
in tropical West Africa, is everywhere a shrub, according to Engler
(1931, p. 347).
Common name.—West African cherry-orange.
A shrub or small tree with solitary
axillary spines, 0.5-2 cm long, even on fruiting branches; leaves large
or very large, 15-33 X 8.5-25 cm, leaflets broadly oval or
oblong-lanceolate, 13-19 X 7.5-10.5 cm, rounded at apex and abruptly
narrowed into a blunt acumen often very short (3-5 mm) but sometimes
longer (8-12 mm) and acute at the very tip, broadly or narrowly cuneate
at base, lateral leaflets slightly smaller than the terminal one,
10.5-15 X 5-7.5 cm, apex like that of terminal leaflets but base more
broadly cuneate or rounded, margins serrulate or shallowly crenulate,
petioles 5.5-8.5 X 1.7-3.5 cm, narrowly elliptical, usually narrowed at
both ends but sometimes broader at the tip or even obovate (as in the
type specimen); inflorescences about 3 cm long (1/3-1/2 as long as the
petiole); flowers white, 4-merous, calyx 4 mm wide, lobes triangular,
acute, petals 4, linear-oblong, 18 X 4 mm, stamens 8, filaments 8 X 1
mm, anthers 3.5 mm long, affixed near the base, disk 1 mm high, ovary
4-locular, ovoid-acuminate, 3-4 mm high, 2.5 mm wide, style long (12-15
mm), slender, expanding gradually and merging with top of ovary, stigma
subglobose, 2.5 mm diam., 4-lobed; fruits subglobose with a truncated,
conical style base, 1.5-2 mm long, persisting at apex.
This was the first species of Citropsis to
be described. It was discovered by P. E. Isert, who called
it a new species of lemon with jointed leaves: "une nouvelle espèce de
citroniers avec des feuilles articulées." One of Isert's
specimens was sent to the herbarium at Berlin, and Willdenow named it Citrus articulata in
1826, but did not describe the flowers, which had perhaps fallen off
the "many-flowered peduncles" he mentioned. In 1895, Engler
proposed as a new species Limonia preussii, found growing on the
shores of Elephant Lake in what is now Cameroon. The
description was the first full and accurate one published of a Citropsis.
The very defective type specimen of Citropsis articulata,
consisting of a short twig and two petioles in the Berlin-Dahlem
herbarium, is all that is known to be extant of Isert’s
material. This type specimen, when studies by Willdenow,
must have been more complete than it is now, for his original
description reads, in translation: "C.[itrus] with large, articulated,
obovate, leaf-like petioles, leaves oblong, peduncles
many-flowered." No inflorescences are now to be seen and no
leaves (or leaflets). Possibly, however, Willdenow mistook
detached oblong petioles for leaves. However, Engler (1915,
p. 758), who had access to the type specimen of Citrus articulata and abundant material of his own species, Limonia preussii, said: "…indeed I cannot avoid combining my Limonia preussii [with Citropsis articulata] as the width of the petiole wing shows no specific differences."
Engler gave C. articulata a very
wide range, from the type locality north of Accra in modern Ghana
through near-by Togo (Koli near Kame) east to what is now Cameroon
(Elephant Lake, type locality of Limonia preussii) and south to the present-day Republic of Congo (Brazzaville) and the Republic of the Congo (Leopoldville) (including Limonia demeusii De Wild. and L. poggei Engl.,
of which the flowers are not yet know). Future study of
flowering material is needed, however, to determine whether C. articulata has so wide a range or not.
For the present, Engler's view concerning the identity of C. articulata is accepted, but flowering specimens from the type locality might even show it to be identical with C. mirabilis, native to the ivory Coast, adjoining Ghana to the west, in which event the name C. preussii would be applied to what is here called C. articulata.
Citropsis preussii, here considered as synonymous with C. articulata, is a shrub with very large leaves, nearly as large as those of C. gilletiana, which grows to be a tree sometimes 10 meters high.
4. Citropsis mirabilis (A. Chev.) Swing. & M. Kell. Jour. Agr. Res. 1:432. 1914. Limonia mirabilis A. Chev. Bul. Soc. Bot. France 58(mem. 8d):144. 1912. Illus. Swingle & M. Kellerman, loc. cit. p. 425, fig. 4,B (pistil only); Engler, Die Nat. Pflanzenfam. 19a:348, fig. 158,J (copy of above). 1931.
Type.—West Africa, Ivory Coast,
between Sanroa and Quode on Koué River (an affluent of the Sassandra
River) (Chevalier, 1909, No. 21609). Herb. Chev., Paris.
Distribution.—West Africa: Ivory Coast. Up to now this species was known only from the type locality.
Common name.—Ivory Coast cherry-orange.
A much-branched and very spiny shrub, 2-5
m high, completely glabrous, spines 2-4 cm long; leaves 3-5-foliolate,
leaflets oblong or broad-elliptical, 9-16 X 5-9 cm, the terminal leaflet
larger than the lateral ones, apex narrowed into a short, blunt acumen,
base cuneate or badly rounded (when the terminal leaflet is borne
singly on a short rachis segment, as in some 3-foliolate leaves);
inflorescences small (5-10-flowered), axillary racemes, 2-3.5 cm long,
pedicels slender, 3-5 mm long, 0.5 mm wide at base and gradually
expanding to 1 mm diam. at top; flowers white, 4- (rarely 5-) merous,
sepals greenish, 1 mm long, petals linear, 13-15 X 4-5 mm, soon falling,
stamens free, filaments flattened, disk very short (0.5 mm), forming a
loose, very shallow cup (0.2-0.3 mm deep) at base of ovary, pistil in
fully developed flowers 11-13 mm long (including disk), ovary slender,
2-2.5 X 1-1.2 mm, style 6-9 mm long, slender at base (0.2-0.3 mm diam.),
gradually expanding upward to 0.6-0.7 mm at top, stigma 0.5-0.8 mm
high, 1-1.2 mm wide, 4-lobed, with 2 small oil glands in each space
between stylar canals; fruits (only immature seen) borne on pedicels.
This species much resembles C. articulata,
differing chiefly in the somewhat shorter style not expanding at the
base and not merging into the top of the ovary. Possibly C. mirabilis, when better understood, will be ranked as a variety of C. articulata occupying the westernmost part of its wide range.
5. Citropsis gilletiana Swing. & M. Kell. Jour. Arnold Arbor. 21:116. 1940. Illus. "W. G. S[mith (?)]," Gard. Chron. 3 ser. 53:378, fig. 159. 1913; Goossens, Bul. Agr. Congo Belge 15:161, fig. 45. 1924; Swingle & M. Kellerman, loc. cit. pl. 1, figs. 1-7; pl. 2, figs. 1-5; fig. 3-25 this work.
Type.—Washington, D.C., Bureau of
Plant Industry greenhouse, tree grown from seeds sent by Père J. Gillet
from type locality, Kisantu, Belgian Congo (Swingle, C.P.B. No. 7800 G =
P.E.I. No. 109622), flowering branch; also several paratypes of leafy
shoots, flowering and fruiting branches, fruit, etc., cut from type
tree; photographs and serial microtome sections S. and T. Nos. 501-A,
501-B, 501-C, and 501-D, 40 slides with 1,339 sections from type tree,
in Herb. Natl. Arbor., Washington, D.C.
Topotypes.—Belgian Congo, Kisantu,
Jardin Botanique (J. Gillet); 2 branches with very young fruits, March
5, 1913, in Herb. Natl. Arbor., Washington, D.C.
Distribution.—Reported (Goossens,
1924, p. 162) from Ubangi and Equateur regions of northwestern Belgian
Congo (now Republic of the Congo) and cultivated at the Jardin Botanique
d'Eala.
Common name.—Gillet's cherry-orange.
Tree 8-10 m tall, young branches
glabrous, 2.5-4 mm diam., internodes 2-6.5 (usually 3.5-4.5) cm long,
spines slender, acute, 2-5 cm long, solitary or in pairs; leaves very
large, 3-5-foliolate, 16-37.5 X 10-36 cm, terminal leaflets 9-21 X 5-14
cm, lateral ones (always smaller than the terminal) 7-17 X 4-9.5 cm,
petioles obovate, 6-10 X 3.5-7.2 cm, rachis segments (1 or 2) elliptical
or obovate, 3.5-9.5 X 1-5-7.5 cm (usually 3.5-6 X 1.5-4 cm);
inflorescences racemose, axillary, short, 5-12 mm long, flower pedicels
3-5 mm long; flowers white, numerous, about 2.5 cm diam., but often
opening incompletely because densely crowded in short inflorescences
4-parted, calyx lobes triangular, acute, 2 X 2 mm, petals 16-18 X
4.5-5.2 mm, stamens 8, filaments glabrous, flattened, free, disk 0.8-0.9
mm high, 2.2-2.4 mm wide, cupulate (0.3 mm deep), pistil (including
disk) 10-13 mm long, ovary ovoid or barrel-shaped, 3.5-4 X 2.5-3 mm,
4-locular, locules with 1 ovule, style 4.5-6 X 1.2-1.3 mm, stigma
depressed globose, 1.2-1.3 mm high, 2.5 mm wide; fruits subglobose,
24-25 mm diam., with pedicels 7-9 mm long, lemon-colored when ripe, peel
thin (1-1.5 mm), locules with very numerous pulp-vesicles filled with
granules of yellowish wax; seeds white, smooth, usually 2-3 (often
none), ovoid, 9.5-10 X 5-6 mm, testa very hard, hilum ovate, 1-2 mm
diam. with smooth edges, monoembryonic.
The type tree of C. gilletiana was
grown in the citrus greenhouse of the former Bureau of Plant Industry
from seeds received from Père Gillet in March, 1913. Unlike C. schweinfurthii,
growing alongside in the greenhouse, the young tree did not flower for
many years and then only sparingly; later it flowered and fruited
profusely. The type tree produced enormous leaves, both
trifoliolate and 5-foliolate. A trifoliolate leaf at the
base of a vigorous water sprout was 28.5 cm long and 31 cm
wide. The terminal leaflet measured 20.5 by 14 cm, the two
lateral leaflets 16.5 by 9.5 cm. The largest leaflets have 7
to 10 principal lateral veins, raised on the under surface and sunken
on the upper surface. The surface of the leaflet is usually
more or less bullate because of the upward curving of areas of the leaf
surface limited by the principal lateral veins and their cross
veinlets. The winged petiole, cordate in outline, measured
8.5 by 7.2 cm. A large 5-foliolate leaf higher up on the
same shoot measured 37.5 cm long and 36 cm wide; the terminal leaflet
(somewhat deformed) was 18 by 10 cm. The two higher lateral
leaflets were 18.5 to 19 by 10.5 to 11 cm. One of the lower
leaflets measured 16 by 10.25 cm (the other was imperfect).
The elongate-elliptical winged rachis segments measured 9.5 by 4.5 cm,
the elliptical winged petiole about 10 cm long and about 7.5 cm wide
(one side defective). These are the largest leaves yet
reported on either a Near-Citrus or a True Citrus Fruit Tree, though
they are greatly exceeded in size by the leaves of some species of Clausena.
In trifoliolate leaves, the terminal
leaflet is usually decidedly longer than the adjoining laterals and
frequently much wider, from one-fourth to one-third or even more; when
the terminal leaflet, as often happens, is borne on a separate winged
rachis segment, it is sometimes even two-fifths wider.
The stigma in cross section shows eight
small oil glands (two between each pair of stylar canals).
The fruits are often crowded, three to six in a dense cluster in the
axils of the leaves of the fruiting branches; they are usually
subglobose, 2 to 2.5 cm in diameter, but are sometimes
depressed-globose, 2 cm long and 2.3 to 2.4 cm wide; they become
yellow-orange and are fragrant when ripe (see fig. 3-25).
Gillet’s cherry-orange, the largest and most vigorous of all the known forms of the genus Citropsis,
has been reported by Belgian expert horticulturists and pathologists
(Goossens, 1924, pp. 156-62, figs. 42-45: Staner, 1929, pp. 364-66, fig.
170; and Pynaert, 1935, pp. 305-14), on the basis of experiments
carried out at the Eala Botanic Garden near Equatorville in Belgian
Congo (now the Republic of the Congo), to be immune to a very
destructive form or foot rot, supposed to be caused by the brown-rot
fungus (Phytophthora citrophthora), that attacks the lower trunks and upper roots of the species of Citrus grown in the Congo, including the sour orange, Citrus aurantium,
usually found to be very resistant to foot rot (see Fawcett, 1936, p.
177). It appears that in the Congo foot rot is greatly
aggravated in severity by the larvae of a longicorn beetle, Monohammus
sp. (see Goossens, 1924, p. 159, and Staner, 1929, pp. 365-66), which
attacks first the cambium layer and later the wood of the base of the
trunk. Citropsis gilletiana, besides being immune to the attacks of the foot-rot fungus, is not attacked by this beetle. It has been found
that Gillet's cherry-orange makes an excellent rootstock for the
cultivated varieties of sweet orange, mandarin, grapefruit, and lemon
which were all found to grow more vigorously when grafted on Gillet's
cherry-orange than on sour orange rootstocks. Furthermore,
citrus trees grafted on Gillet's cherry-orange rootstocks were
completely immune to the Monohammus beetle and also to foot rot,
provided the Gillet's cherry-orange stocks were grafted high enough
above the ground to prevent infection from the soil.
Pynaert (1935, p. 313) reported that the native Citropsis growing
about the Eala Botanic Garden in Belgian Congo had been introduced into
Belgium, and that a Jaffa orange grafted on a plant of Citropsis growing
in a greenhouse of the Colonial Garden at Laeken, Belgium, had made a
particularly vigorous growth and in 1935, when still only 2 meters high,
had produced a number of fruits. An excellent half-tone
figure of the wild Citropsis found near the Botanic Garden in
Belgian Congo, published by Goossens (1924, p. 161, fig. 45), shows
clearly that this cherry-orange is the same as the one sent to Swingle
by Père Gillet from Kisantu, about 700 kilometers down the Congo River
from Eala. It has the terminal leaflet distinctly larger
than the laterals, agreeing with C. gilletiana (but not with C. latialata). Goossens reported that near Eala this Citropsis is
a tree growing to a height of 8 to 10 meters (26 to 33 feet) that bears
tiny, orange-like fruits, 2 to 2.5 cm in diameter, with a resinous,
fragrant pulp in which three or four seeds are imbedded. The
fruits produced by the type tree of Gillet's cherry-orange growing in
the citrus greenhouse at Washington agreed very closely with those
described by Goossens, and the foliage, spines, and fruit clusters of
this type tree resembled exactly what is shown in Goossen’s photograph
of the Citropsis growing wild about Eala.
6. Citropsis latialata (De Wild.) Swing. & M. Kell. Jour. Wash. Acad. Sci. 28:533. 1938. Limonia poggei var. latialata De Wild. Ann. Mus. Congo Bot. 5 sér.1:160. 1904. Illus. De Wildeman, loc. cit. pl. 43; Swingle & M. Kellerman, Jour. Arnold Arbor. 21:pl. 2, figs. 6-10. 1940; fig. 3-26 this work.
Type.—Ikongu village, Sankuru
River basin, Lualaba-Kasai district, south-central Belgian Congo (L.
Gentil. No. 1). Herb. Jard. Bot. l'Etat Brussels;
photographs and serial microtome sections, S. and T. No. 397-A, slides
1-6, 429 cross sections, and No. 397-B, slides 1-2, 26 longitudinal
sections of a mature flower from the type specimen, in Herb. Natl.
Arbor., Washington, D.C.
Distribution.—Known with certainty only from the type collection.
Common name.—Ikongu cherry-orange.
De Wildeman's original French description of Limonia poggei var. latialata reads,
translated, as follows: "Shrub 3-4 m tall, with slender, cylindric
branches, with imparipinnate leaves, having 2 pairs of lateral
leaflets. Leaves distant 1-5 cm from each other, with the
petiole and rachis winged; petioles 3-8.5 cm long and 1.5-5 cm broad,
upper [pair of] leaflets distant 2-8.5 cm from the lower [pair of]
leaflets; rachis reaching 4.5 cm in width. Leaflets oblong,
narrowed into a very short petiolule at the base, cuneate at the apex
and at the base, the midrib dividing the leaflet in 2 more or less
unequal parts. Leaf-blades 6-15 cm long and 2-7 cm wide,
irregularly denticulate on the margins; the terminal leaflet regular,
cuneiform at the base, of the same size as the lateral leaflets;
axillary stipules changed into solitary or paired thorns, more or less
developed, reaching 2.5 cm in length. Flowers white, with
the odor of orange [flowers], in axillary or terminal inflorescences;
ovaries ovoid, terminated by a style twice as long, surmounted by a
trilobed stigma."
A note states that the type material (L.
Gentil, No. 1) was in flower when collected but "the petals fell off
during the preparation." Evidently the flowers were mature.
A single flower from the type specimen (see Swingle, 1940c,
p. 120) was restored by the modified Juel method, imbedded in paraffin,
and cut into serial microtome sections. First 26
longitudinal sections were cut until a section was obtained exactly
through the center; then the paraffin block was turned at right angles
and 429 cross sections 20 mu thick were cut, including the entire
length of the pistil, disk, calyx, and pedicel. These
sections give the following characters:
Calyx is 4-merous, the lobes about 1.2 mm
wide and 1.5 mm long, thick in the middle but with thin edges; disk
shallow, cup-shaped, 0.3-0.4 mm tall and 1.1-1.2 mm wide, pistil 6.4 mm
tall, including the short (1 mm), very shallowly cupulate disk, ovary
ovoid, 1.8 mm tall and 1.6 mm wide, merging rather abruptly into the
style, which is 0.8 mm diam. at the junction with the ovary and nearly 1
mm diam. at the stigmatic junction; stigma cushion-shaped, 1.5 mm wide
and 0.5-0.6 mm high, more or less 4-lobed, with 4 medium-sized oil
glands between the 4 stylar canals.
Thanks to the generous loan by Dr. W.
Robyns, director of the National Botanic Garden at Brussels, of one of
the very few flowers of the type specimen, it was possible to clear up
the long-standing confusion of this species with C. gilletiana, from which it can now be clearly distinguished by many characters of high taxonomic value in this genus. Citropsis latialata
is a shrub only 3 or 4 meters tall instead of a tree 8 to 10 meters
high, it has somewhat narrower leaflets and the terminal leaflet is of
the same size or only very slightly larger than the adjacent lateral
leaflets (in C. gilletiana, on the contrary, the terminal leaflet is always larger than the lateral ones). The pistil of C. latialata is only a little more than half as long as that of C. gilletiana
and has a decidedly shorter and much less deeply cupped nectary, as
well as a more flattened stigma with fewer but larger oil glands.
The long-standing confusion of these two
species was due, without doubt, to the very scanty type material of C. latialata and
the lack of any other material of this species from the type
locality. De Wildeman's excellent lithographic plate
figuring the type specimen of C. latialata, natural size, shows
five pistils in a close cluster at the end of a leafy twig.
This is fully confirmed by a photograph of the type filed in the
herbarium of the National Arboretum. These pistils must have
been full grown, as the petals were in place when the material was
collected, but fell off during the drying of the type
specimen. As noted above, a single flower from the type
specimen sufficed to distinguish clearly the two species C. latialata and C. gilletiana.
Subgenus Afrocitrus
Subgenus Afrocitrus Swing. & M. Kell. Jour. Arnold Arbor. 21:126. 1940.
Leaflets small, acuminate or caudate at
apex, petioles and rachis segments narrowly winged or wingless; ovary
clavate or obovoid, with a single very large oil gland at the top of
each locule; stigma subglobose, distended by large oil glands; staminal
filaments sparsely pubescent on inner side.
The three species that constitute this subgenus, Citropsis gabunensis (type of Afrocitrus), C. zenkeri, and C. le-testui, are easily distinguished from all the other species of Citropsis
by their long, acuminate leaves, narrowly winged or wingless petioles
and rachis segments, and the striking ovary and stigma characters.
Citropsis tanakae also has very
small flowers borne on slender pedicels and very slender styles each
ending in a subglobose stigma swollen by several large oil glands, all
of which are characters very like those of the three species named
above. However, C. tanakae differs from them in
lacking the large oil glands at the tip of the ovary, one over each
locule, and also in having simple leaves with very short, wingless
petioles, not articulated with the leaf blade.
7. Citropsis gabunensis (Engl.) Swing. & M. Kell. Jour. Agr. Res. 1:430. 1914. Limonia gabunensis Engl. Notitzbl. Bot. Gart. Berlin 1:28. 1895. Illus. Swingle & M. Kellerman, loc. cit. 425, fig. 4,D-E; De Wildeman, Ann. Mus. Congo Bot. 5 sér. 1:pl. 50. 1904; Engler, Die Pflanzenwelt Afrikas 3:760, fig. 354,L,N. 1915; Engler, Die Nat. Pflanzenfam. 19a:348, fig. 158,L,N (last two, copies of Swingle & Kellerman). 1931; fig. 3-27 this work.
Type.—Sibange Farm, Menda region near Libreville, Gabon, French Congo (H. Soyaux, No. 105).
Distribution.—Gabon Republic, Republic of the Congo, and Spanish Guinea.
Common name.—Gabon cherry-orange.
A shrub or small tree, 1.5-6 m high,
ultimate branches slender, 1.5-3 mm diam., with internodes 2-5 cm long,
with single or paired slender spines, 2-2.5 cm long even on fruiting
branches; leaves glabrous, 1-5 foliolate, variable in size, 5-foliolate
leaves 15.5-19 X 12-15 cm, 3-foliolate leaves 10-13 X 7-10 cm,
1-foliolate leaves 12-17 X 4-7 cm (including the petiole 2-4 cm long),
leaflets oblong or elliptical, long-acuminate at the apex or caudate,
very variable in size, 1-foliolate leaflets very large, blade 7-14.5 X
3-7 cm, petiole 2-3.5 X 0.4-1.5 cm, with a broadly rounded base,
5-foliolate leaflets usually 8-10 X 4-5 cm, but sometimes smaller, 3.5-8
X 1.5-3.5 cm, terminal leaflet often borne on a short rachis segment
and then abruptly narrowed at base, but if borne at apex of first rachis
segment with 2 lateral leaflets then narrowly cuneate or acuminate at
base and longer than lateral leaflets, petioles variable in size and
shape, 1.8-5 X 0.3-2 cm, linear or narrowly elliptical if narrow,
obovate if broad, rachis segments often similar in shape to petiole,
3.5-5.5 X 0.4-2 cm; inflorescences short, axillary flower clusters,
1.5-2.5 cm long, peduncles apparently unbranched, 8-9 mm long, pedicels
long and very slender, 7-11 X 0.4-0.6 mm (in dry state),
short-pubescent, flowers very small, usually 4-merous, buds 5-6 X 2 mm,
open flowers about 10-13 mm diam., calyx lobes 4, triangular, acute,
with a single medium-sized oil gland near the apex, petals 4, about 6 X
2.5 mm, stamens free, filaments flattened, sparingly pubescent on inner
side; disk very small, about 0.5 mm high, pistil very short (4-6 mm,
including the disk), ovary obovoid, about 1.5 X 0.8-0.9 mm, 3-4-locular
with a large, more or less protuberant oil gland at the top of each
locule, style very slender, not expanded at base, about 2 mm long,
0.3-0.4 mm diam., stigma subglobose, 0.9-1 mm diam., slightly 4-lobed,
with about 4 large oil glands; fruits subglobose, about 1.8-2.2 cm;
borne on pedicels 8-12 X 1-2 mm, nearly filled with 3 or 4 ovoid,
smooth, hard seeds, 10-12 X 8-10 X 6-8 mm, with an even-margined hilum 2
X 1 mm, pulp-vesicles almost suppressed the seeds in most fruits.
This species is the type of the subgenus Afrocitrus, which includes also C. zenkeri and C. le-testui. These three species are evidently related to each other and clearly delimited from the six typical species in the subgenus Citropsis.
Citropsis gabunensis has very small flowers, the smallest of any species of the genus. No other species of Citropsis shows
as much variation in the number and size of the leaflets.
The type material from Sibange Farm, Gabon (and also abundant material
collected by Père Klaine near Libreville, Gabon, now in the Paris
herbarium), shows whole branches with very large unifoliolate leaves,
although more often some of the leaves have two or three
leaflets. The typical 5-foliolate form is also common at
both places; it often shows a short winged rachis segment bearing the
terminal leaflet, something found only in trifoliolate leaves of other
species of Citropsis. The large unifoliolate leaves look astonishingly like those of Citrus in every character—size, shape, venation, texture, and color; they even have winged petioles very like those of some forms of Citrus aurantium and C. grandis.
The unifoliolate species of Pleiospermium, P. sumatranum, P. longisepalum, and P. latialatum, also have leaves very like those of Citrus and closely resembling those found on this form of Citropsis gabunensis. Doubtless both Citropsis and Pleiospermium contain species that resemble closely remote ancestral forms from which Citrus has evolved.
7a. Citropsis gabunensis var. lacourtiana (De Wild.) Swing. & M. Kell. Jour. Arnold Arbor. 21:124. 1940. Limonia lacourtiana De Wild. Ann. Mus. Congo Bot. 5 sér. 1:159. 1904. Illus. De Wildeman, loc. cit. pl. 50.
Type.—Bombay, Sankuru
(Lualaba-Kasai), south-central Belgian Congo (L. Gentil, No. 1), Herb.
Jard. Bot. l'Etat, Brussels; photographs and serial microtome sections
of type specimens, S. and T. Nos. 532-A, 533-A, 533-B, 533-C, and 533-D,
18 slides; also leafy twig and fruit of type collection, in Herb. Natl.
Arbor., Washington, D.C.
Distribution.—Republic of the Congo: known only from the type locality in the Sankuru River valley.
Common name.—Sankuru cherry-orange.
Fruits subglobose, 1.8-2 cm diam.,
yellow-orange when ripe, peel 2-2.5 mm thick, rather soft, pulpy tender,
juicy, and of very agreeable flavor, seeds few or none, plump,
subglobose, bluntly conical at one end, 11 X 9-10 mm.
The type specimen of Limonia lacourtiana
was kindly lent to Swingle by Dr. W. Robyns, director of the Jardin
Botanique de l'Etat at Brussels. It consists of a single
fruiting branch collected in May, 1902, with a number of half-grown and
three nearly mature fruits, most of them seedless, but one (or two?)
with a single yellowish-brown (Buckthorn brown, Ridgway, 1912, pl. 15),
rather large, plump, short-ovoid seed, 11 by 8.5 to 9 mm, with a hard
testa having a smooth-edged, ovate hilum 2 by 1 mm. Gentil's
original field label attached to the type sheet calls the plant "un
mandarinier sauvage" and notes its "fruit délicieux." The
three to six fruits occur together in dense axillary clusters and are
borne on pedicels 8 to 13 mm long, which in turn are densely crowded on a
very short peduncle only 4 to 10 mm long.
Three topotype specimens in the herbarium
of the National Botanic Garden at Brussels collected nearly a year
later by Em. and M. Laurent consist of two sterile branches with paired
axillary spines, 2 to 2.5 cm long, and a fruiting branch from a small
tree, 6 to 7 m high, looking extremely similar to the type specimen,
with eight immature fruits, all but one of them seedless.
Flowers of the variety are unknown, but a
specimen in the Brussels herbarium from the same general Sankuru
region, collected by A. Sapin in September, 1906, consists of two
flowering twigs with axillary clusters containing three to six very
small flower buds, about 5 by 3 mm, with slender pedicels, 0.4 to 0.6 mm
diam. These have pistils (immature?) which when restored by
the modified Juel technique measured 4.4 mm long (including the disk);
disk 0.6 to 0.7 mm high, 1 to 1.25 mm wide, cupulate, enclosing narrowed
base of ovary for 0.2 to 0.25 mm; walls of the cup unusually thick (0.4
to 0.6 mm), containing six to ten medium-sized oil glands arranged
approximately in a ring at a level even with or slightly below the
bottom of the cup; ovary 3-locular, 1.3 mm long, 1.1 mm wide at top, 0.5
mm wide at bottom, with a medium-sized oil gland at the top of each
locule; style 2 mm long, 0.5 to 0.6 mm wide; stigma 1 mm long, 1.2 mm
wide, with large oil glands between the stylar canals. The
anthers have a single large oil gland near the tip of the
connective. These measurements and the disposition of the
oil glands in the ovary, stigma, and anthers agree very closely with
those found in the flower buds of a specimen of typical C. gabunensis preserved
in the herbarium of the Museum of Natural History at Paris, collected
by Père Klaine at Libreville, Gabon. However, Sapin’s
material from Sankuru has glabrous staminal filaments, whereas those of
the species have scattered, slender hairs on the side facing the ovary,
as do those of C. le-testui. If this absence of
pubescence on the filaments of the variety is found to be a constant
character, it will be useful in separating it from the species at
seasons when no mature fruits are to be found.
The two species of Citropsis that have and fruited in the United States, C. schweinfurthii and C. gilletiana,
both produce an abundance of small orange-like fruits, but they are not
edible, as the pulp-vesicles contain numerous granules of a waxy
substance of disagreeable flavor. Doubtless C. gabunensis, belonging as it does to a very different group (the type of the subgenus Afrocitrus
discussed above), does not produce this ill-flavored wax.
The species itself has fruits so full of plump seeds as to leave very
little space for pulp. The variety lacourtiana, on the contrary, has seedless fruits that are filled with high-flavored pulp.
8. Citropsis zenkeri Engler, Die Pflanzenwelt Afrikas 3(Heft 1):760. 1915. Illus. Engler, loc. cit. p. 759, fig. 354,A-E; Engler, Die Nat. Pflanzenfam. 19a:348, fig. 158;A-F. 1931.
Type.—Bipindi, southern Cameroons (Lat. 3° 20' N., Long. 11° 45' E.). Herb. Bot. Mus., Dahlem-Berlin.
Distribution.—Known only from the type locality.
Common name.—Zenker's cherry-orange.
Fruiting twigs with slender, acute,
solitary, axillary spines, 1.5-2.5 cm long and 2-2.5 mm diam. at base;
leaves 5-foliolate, 25 X 23 cm, leaflets 11-13 X 5-5.8 cm,
ovate-acuminate or short-caudate, acumen 15-20 X 4-1 mm, acute at apex,
base broadly cuneate, with very short (1-2.5 mm) petiolules, petiole
5.5-6 cm long, narrowly winged, 3-4 mm wide on either side of the
midrib, rachis segments about 5 cm long, narrowly winged, total width at
broadest place, 8-9 mm; inflorescences short, axillary clusters of
numerous flowers with pedicels 3-4 X 0.5-0.7 mm, borne in dense clusters
(5-8?) on short, unbranched, glabrous peduncles, 3-4 mm long; flowers
medium-sized, 15-18 mm broad when open, 4-merous, calyx lobes deltoid,
bluntly pointed, roughened on the back by numerous oil glands, petals
tapering regularly to an acute apex, 8-10 mm long, with numerous oil
glands, stamens 5-6 mm long, anthers 3-3.5 mm long, pistil 7.5-8 mm long
(including short, narrow disk), ovary obovoid, 4-locular, 2-3 mm long,
0.6-0.8 mm wide at base but expanded at apex to 1.5-2 mm in width by 4
large protuberant oil glands (1 at the top of each locate), style
cylindrical, not expanded at junction with the tip of the ovule, 3.5-4
mm long (including the stigma), 0.4-0.5 mm wide, stigma subglobose, 1.5
mm diam., obscurely 4-lobed, swollen with 4 large oil glands.
This description is based partly on the
short original description but mostly on the excellent illustrations
that accompany it (Engler, 1915), which are made more valuable by
comparable figures of five other species of Citropsis.
The Zenker's cherry-orange is evidently closely related to C. gabunensis and to C. le-testui,
but has even larger, more protuberant oil glands at the top of the
ovary above each locule. The fruits are unknown, but should
be collected in the hope of finding an edible form with few seeds like C. gabunensis var. lacourtiana.
9. Citropsis le-testui Pellegrin, Bul. Mus. Hist. Nat. Paris 27:446. 1921. Illus. Pellegrin, Mém. Soc. Linn. Normandie 26:42, fig. 3. 1924.
Type.—Ndougou in Ngouyé Valley,
French Congo (Lat. 2°-3° S., Long. 10° 30' E.) (Le Testu, No.
2286). Herb. Mus. Hist. Nat., Paris; photographs of type,
also 2 leaflets and 3 flower buds of type material with serial microtome
sections of 1 bud, S. and T. Nos. 708-A (9 slides, cross sections),
708-B (3 slides, longitudinal sections), in Herb. Natl. Arbor.,
Washington, D.C.
Distribution.—Known only from the type locality.
Common name.—Le Testu's cherry-orange.
The original description, translated (and
slightly amended from the equally detailed French redescription
published (3 years later, in 1924) reads: "A small tree, 3 meters high,
branches gray-green, glabrous, slender, more or less spiny.
Spines 1 or 2, erect, axillary, 2-3 cm long. Leaves usually
3-foliolate, sometimes 5-foliolate ([the two pairs] separated 3-6
cm). Petiole nearly terete, glabrous, 6-8 cm long (or in
5-foliolate leaves, 12-15 cm long), articulated with the rachis
segment. Leaflets ovate, 6-12 cm long, 3.5-7.5 cm wide, apex
attenuate-acuminate, acumen obtuse, 1-2 cm long, abruptly contracted at
base into a petiolule 3-4 mm long, glabrous, rigid, membranaceous,
glandulose-punctate, midrib prominent below, depressed above, 6 primary
lateral veins on each side, ascending and anastomosing far from the
margin then curving to meet it, the smaller veinlets reticulate,
slender, prominent below in dried specimens. Inflorescences
short, axillary panicles, very shortly tomentose, peduncles 0.8 mm long,
pedicels 5 mm long. Bracts ovate, acute, 1 mm
long. Calyx thick, glandulose, shortly-villose without,
4-lobed, lobes deltoid, acute, 2 mm long with scarious
margins. Petals 4, glandulose, glabrous, oblong, concave,
apex subangulate, 7 mm long, 3.5 mm wide. Stamens 8,
filaments linear-lanceolate, flattened, shortly-villose, 4 mm long,
anthers introrse, glabrescent, 4 mm long, oblong-saggitate [sic],
apex acute and long-acuminate. Disk prismatic, apex
somewhat 4-lobed, 1 mm high, glandulose, glabrous. Ovary
glandulose, glabrous, obpyramidal, somewhat 4-lobed at the apex, 2 mm
high, 4-locular, locules 1-ovulate; style terete, glabrous, 2-3 mm high,
stigma capitate, somewhat 4-lobed. Fruit subglobose,
slightly flattened at the apex, 1.5 cm high, 2 cm broad."
Pellegrin in his comments following the
description stated that the flowers are white, the leaves usually
3-foliolate. Citropsis le-testui is a small tree, 3 m
high, relatively abundant on the slopes of the hills, and never seen
growing in wet situations; the fruit is yellow when ripe.
This remarkable species differs from all others of the genus Citropsis in
having completely wingless petioles and rachis segments, which gives
the leaves a curious aspect. As noted by Pellegrin, the
leaves of this species much resemble those of Balsamocitrus dawei, a very different plant of the subtribe Balsamocitrinae, not at all closely related to Citropsis.
The figure of C. le-testui cited
above shows the stamen to be 8 mm long, the filament flattened, about 4
mm long, 0.75 mm wide, 0.5 mm thick at the widest part, and
short-pubescent on the inner side. The anther is shown to be
about 3 to 3.2 mm long, 1 mm wide, and 0.75 mm thick, tapering to a
sharp point at the apex.
Fortunately, a flower bud ready to open
was available for study from the type specimen. After being
restored by the modified Juel technique and cut into serial microtome
sections, the following characters of the flower parts were observed:
Nearly mature flower buds 9-10 X 4-5 mm;
calyx lobes 3 (4?), 1 mm wide, 1.5 mm long, subacute, much thickened by
numerous oil glands which are larger and more closely juxtaposed in the
free lobes; corolla 3- (4-?) merous, petals linear, 9-10 X 5 mm, with
sparsely scattered, medium-sized oil glands; stamens 8, about 7 mm long,
filaments free, 4-4.5 mm long, subclavate, about 1 mm wide, thickest
near the apex (0.4-0.5 mm), with many slender hyaline, scattered hairs
on the ventral surface (facing the ovary), anthers 3-3.5 mm long,
0.6-0.8 mm wide, with a large, elliptical, acute-pointed oil gland at
the apex, 1 mm long, 0.3-0.4 mm wide; pistil (in nearly mature bud) 7 mm
long (including the disk), disk 1-1.2 mm long, cupulate and enclosing
base of the ovary for about 0.4 mm, without noticeable oil glands; ovary
3- (4-?) locular, obconical, 2.6-3 mm long, 0.5-0.6 mm wide below, at
junction with disk (at bottom of cup), tapering regularly upward, 2 mm
wide at flattened top, which has 1 large, ovoid, somewhat protuberant
oil gland (0.6-0.8 mm diam.) over each locule and numerous smaller oil
glands between them; style arising abruptly, narrowed and slightly
countersunk in the center of the flattish upper face of the ovary, 3-3.2
mm long, 0.5 wide at base, gradually expanding to 0.8 mm wide at
junction with the stigma, sparsely covered with small, scattered,
superficial oil glands; stigma subglobose, 1.2 mm high, 1.5-1.6 mm wide,
with several (4-5?) large oil glands, 0.9-1 mm vertical diam. and
0.3-0.6 mm transverse diam., sometimes smaller (through pairing).
Thanks to this authentic type material, it is possible to assert definitely that the pistil of C. le-testui is very like those of C. gabunensis and C. zenkeri,
and in general is intermediate between them in its
characters. The flat-sided ovary and disk described and
figured by Pellegrin (l.c.) were doubtless distorted by shrinking
suffered during desiccation.
SPECIES INADEQUATELY KNOWN AND OF UNCERTAIN RELATIONSHIPS
10. Citropsis tanakae Swing. & M. Kell. Jour. Arnold Arbor. 21:121. 1940. Illus. Tanaka, Kankitsu No Kenkyû (Citrus Studies) 78, fig. 71, left (as Citropsis citrifolia, a nomen nudum). 1933; Swingle & M. Kellerman, loc. cit. pl. 3, figs. 1-5.
Type.—Africa, Sierra Leone
(Afzelius). Herb. Univ. Uppsala, Sweden; photographs and
serial microtome sections, S. and T. No. 226-A, 3 slides, in Herb. Natl.
Arbor., Washington, D.C.
Distribution.—Known only from the type locality.
Common name.—Sierra Leone cherry-orange.
Ultimate branchlets slender, 1.5-3 mm
diam., with solitary, axillary, slender, short spines, 2-10 mm long;
internodes 2-3 (or 4?) cm long; leaves simple! broadly lanceolate,
tapering gradually, or slightly acuminate, into a short, thick, blunt
acumen, 8-10 X 6-3 (or 4) mm, base broadly cuneate, with the margins
slightly decurrent into upper part of petiole, lateral veins numerous,
10-12 on each side, arising at angles of about 75°-80° with the midrib,
margins regularly but shallowly crenulate on upper half, subentire
below; petioles very short (3.5-4 mm), wingless, slender (1-1.5 mm
wide), glabrous, not articulated with the leaf blade; inflorescences
very short, few-flowered, axillary; flower buds small (immature?), about
8 X 3 mm, borne on short, slender pedicels, 2-3 mm (or more?) long,
0.5-0.75 mm diam.; calyx roughened with numerous oil glands, glabrous,
calyx lobes 4, short (0-3-0.4 mm), with thin scarious edges, with a
single rather large oil gland near the subacute tip, petals 4, about 7 X
3 mm, glabrous, with many medium-sized oil glands, more abundant at the
pointed tips, stamens 8, about 5.5-6 mm long, staminal filaments
glabrous, somewhat flattened radially, broad at the base where they
cohere in groups of 2 or 3 for some distance (about 2.8 mm), anthers
about 3 mm long with a single small oil gland near the top of the
connective; disk cylindrical, glabrous, short, shallow cup-shaped,
fitting rather closely over the base of the ovary for about 0.1 mm, with
a few small oil glands in walls of cup, pistil 5.6 mm long (including
disk), ovary 4-locular, ovoid, 0.93-1 mm long, 0.8-1 mm wide, rounded at
top, without a large oil gland over each locule, style long and slender
(4.6 mm long, 0.3-0.4 mm wide), contracted where it joins the ovary in
which it is very slightly countersunk, slightly expanded at the apex
where it merges into depressed globose stigma, 0.7 mm high and 0.9 mm
wide, containing several (5-7) large oil glands.
This species is known only from a single
twig, about 20 cm long, with seven leaves and a single flower bud,
collected in Sierra Leone between 1794 and 1796 by the Swedish botanist
Afzelius, who identified it as Citrus medica, doubtless because the petioles were not articulated with the leaf.
This unique flower bud and a single leaf
were kindly sent to Washington by the custodian of the herbarium of the
Botanical Museum of the University of Uppsala, Sweden. The
flower bud was cut into 454 serial cross sections, each 20 mu
thick, by a modification of the method published by Juel (1918, p. 14)
while he was professor of botany at the University of
Uppsala. This very old material could not be restored as
well as usual, but nevertheless it was possible to work out the flower
structure in minute detail (see Swingle, 1940c, pl. 3, figs. 1-5) and to draw up the preceding description, which proves beyond doubt that this plant is not a species of Citrus but a new species of Citropsis.
This remarkable species is unique in the
genus because of its simple leaves with very short wingless petioles
(only one-twentieth as long as the leaf blade and not articulated with
it). All other species of Citropsis have odd-pinnate leaves, trifoliolate to 7-foliolate or occasionally (in C. gabunensis)
unifoliolate leaves, with petioles that are, however, very evidently
winged and never less than one-eighth as long as the leaf
blade. In C. le-testui the petioles (and rachis segments) are wingless, but are very many times longer.
The leaves of C. tanakae are very like the leaflets of the other species of Citropsis, which always have very short, wingless, nonarticulated petiolules. Citropsis tanakae has flowers somewhat resembling those of the species in the subgenus Afrocitrus
in having a subglobose stigma distended with large oil glands borne on a
very slender style, but the ovary lacks the large oil glands, one at
the top of each locule, such as characterize the species of this
subgenus.
Besides being one of the most distinct species of the genus, C. tanakae is also the northernmost species in Africa, occurring some 500 to 600 kilometers northwest of C. mirabilis, a very different species, native to the Ivory Coast in West Africa.
This beautiful Sierra Leone cherry-orange
has been named in honor of Professor Tyôzaburô Tanaka, who, as soon as
he saw the type specimen in the Uppsala herbarium, recognized that it
belongs, not to the genus Citrus, as Afzelius supposed, but to Citropsis.
11. Citropsis daweana Swing. & M. Kell. Jour. Arnold Arbor. 21:123. 1940. Illus. Tanaka, Kankitsu No Kenkyû (Citrus Studies) 77, fig. 70, right (sub nomen nudum, Hesperethusa villosa). 1933; Swingle & M. Kellerman, loc. cit. pl. 3, fig. 6; fig. 3-28 this work.
Type.—Madanda Forest, Portuguese
East Africa (Dawe, No. 443). Herb. Brit. Mus., London;
photograph and fragments in Herb. Natl. Arbor., Washington, D.C.
Distribution.—Known only from the type locality (now Mozambique).
Common name.—Mozambique cherry-orange.
A shrub or small tree, 3 -5 m high,
branchlets at first angular, soon cylindrical, 2 -4 mm diam; internodes
2-3 cm long; spines axillary, solitary, short, straight, 1-2.5 cm long,
2-4 mm diam. at base, shorter ones blunt-pointed, the longer ones
(1.5-2.5 cm) sharp-pointed; leaves 5-7-foliolate; leaflets elliptical to
rhomboid or ovate, bluntly rounded at the apex, terminal one narrowly
cuneate at base, 5-5.8 X 2-2.4 cm, lateral ones broadly cuneate or
broadly rounded at base, 2-4.5 X 1.5-2.4, with 4-6 rather inconspicuous
veins, sparsely and evenly dotted with small translucent oil glands,
sparingly pubescent on both sides and on the margins with very slender,
colorless ciliate hairs, margins finely and shallowly crenate or
subentire, petiolules very short (1-1.8 mm); petioles nearly or quite
wingless. 1.2-2.2 cm long, 1-1.5 mm wide; first rachis
segments 1.5-2 cm long, with spathulate wings, 3-6 mm wide and rounded
at the distal end, usually narrowed to a subacuminate base at the
proximal end, second rachis segments elliptical, broader (about 2.5 X
0.8 cm), not spathulate; flowers and fruits unknown.
This remarkable species is known only
from the type material collected by M. T. Dawe (when director of
agriculture of the Companhia de Moçambique) in the Madanda Forest, a
rubber-producing region, which lies 100 to 200 kilometers to the
southwest of Beira, between the Lucite River (Lat. 20° S.) and the Save
River (Lat. 21° 30' S.), to the west of the Sofala lands (about Long.
34° E.) and to the east of the Mossurize district (about Long. 33° E.).
Unfortunately the flowers and fruits of
this species are unknown; however, the leaf characters are so
distinctive that it cannot be mistaken for any other Citropsis. The
leaves, including the petioles and rachis segments, are sparingly
pubescent on both surfaces, whereas in all the other species they are
glabrous; the leaflets are the smallest known in the genus.
The petiole-rachis wings become progressively wider toward the tip of
the leaf, that is, the petiole is wingless or nearly so, the first
rachis segment narrowly winged (wider at the tip), and the second
segment still wider. This is just the reverse of what is
found in the other winged species of Citropsis. The scanty type material seems to show Kurztrieben, like the leaf and flower spurs of Poncirus trifoliata and some of the Hard-Shelled Citroid Fruit Trees (subtribe Balsamocitrinae).
The leaf, petiole, and rachis characters
of this species show a great similarity to those of certain forms of Hesperethusa crenulata from peninsular India. However, as noted above, certain forms of Citropsis gabunensis have leaves and petioles greatly resembling those of Citrus but have flowers and fruits unmistakably belonging to Citropsis. Only the study of flowers and fruits can reveal the exact relationships of C. daweana.
The Mozambique cherry-orange has the
appearance of being a somewhat xerophytic plant; the other species are
evidently mesophytes and usually grow in tropical rain forests.
This is without question the least known species of the genus Citropsis and
at the same time the most distinct one! When flowers and
fruits are available for study it will very probably be found to
constitute a new subgenus, if not a new genus. It is of
great phylogenetic interest as a measure of the nature and rate of
evolution that has occurred since Citropsis was cut off from any connection with its relatives in southeastern Asia, eastern India, and the Monsoon region.
XX. Atalantia Corrêa
XX. Atalantia Corrêa, Ann. Mus. Hist. Nat. Paris 6:383. 1805. Rissoa Arn. Nov. Act Acad. Caes. Leop.-Carol 18:324. 1836; Malnarega Raf. Sylv. Tell. Mant. 143. 1838.
Type species.—Limonia monophylla Roxb. non (L.) = Atalantia monophylla DC.
Distribution.—Southwestern Asia:
India, Ceylon, Burma, Cambodia, Laos, North Vietnam, South Vietnam,
southern China; also Sumatra, Banka (?), Java (?).
Common name.—Atalantia.
Small trees or shrubs, twigs more or less
angled when young, soon cylindrical, glabrous in some species, more or
less hairy when young, with single, stout, sharp spines in the axils of
the leaves, or spineless, especially fruiting branches of old trees
(some species [A. rotundifolia] nearly spineless); leaves
1-foliolate (or rarely simple), more or less coriaceous, strongly
veined, and usually with conspicuous reticulations between the lateral
veins; petioles wingless, often pubescent when young, articulated with
the leaf blade, short, often less than 1/10 as long as the leaf blade;
flowers small, axillary or rarely terminal, fascicled, or in racemose
corymbs or panicles; calyx 3-5-lobed, or forming a continuous envelope
over the corolla, stamens, and pistil, and splitting more or less
irregularly into 2 or 3 parts as the flower expands; petals imbricate;
stamens 6-10, free, or more or less connate into a staminal tube which
is sometimes a closed cylinder with the anthers attached to the rim;
anthers short, broadly ovoid; disk annular, short; ovary ovate, or
subglobose, with 3-5 locules, with 1 or 2 ovules in each locule; fruits
small, subglobose, with numerous broad-based, sessile, slender, tapering
pulp-vesicles filling all the space in the segments left by the seeds;
peel thin, greenish-yellow on ripe fruit, dotted with oil glands; seeds
oblong, green within, sometime polyembryonic.
The genus Atalantia contains small trees somewhat resembling Citrus in
general aspect, bearing fragrant white flowers and globose fruits with
the appearance of diminutive greenish-yellow oranges. The
pulp-vesicles are, however, different from those of Citrus in being sessile instead of stalked. The leaves of Atalantia, although almost always unifoliolate like those of Citrus,
are very different in having much more prominent, more numerous lateral
veins, and veinlets forming reticulations between the lateral veins.
Besides the typical species of Atalantia, which have numerous sessile, conical pulp-vesicles, there are at least two species which belong to the subgenus Rissoa, based on the type species A. ceylanica.
This species has very large seeds which almost completely fill the
locules of the fruit, leaving very little space for
pulp-vesicles. Atalantia rotundifolia is closely related to A. ceylanica and is perhaps a spineless brachytic mutation of it. A third species, A. guillaumini, somewhat resembles A. ceylanica
and like it has large seeds almost completely filling the locules of
the fruit. However, so far as could be determined from the
scanty fruits examined, no pulp-vesicles are present. It may
be found that there has been an evolutionary tendency of the species of
the subgenus Rissoa to lose the pulp-vesicles, resulting in the development of completely pulpless species obviously closely related to Atalantia in spite of lacking one of the most important characters of the genus and even of the subtribe Citrinae.
It has in the past been supposed that the genus Atalantia was founded by Corrêa da Serra to include Limonia monophylla L., now believed to be a synonym of A. ceylanica. Corrêa cited no species under his new genus Atalantia but almost certainly had in mind the "Limonia monophylla
L." described and figured by Roxburgh (1795, vol. 1, pp.59-60, pl. 83),
since he spoke in detail of "singular monadelphy" of the stamens with
the filaments fused into a complete cylinder, just as had been figured
by Roxburgh ten years previously. That he was familiar with
Roxburgh's great work on Plants of the Coast of Coromandel is shown by the fact that immediately after discussing the genus Atalantia he mentioned Limonia arborea and L. pentaphylla of Roxburgh (two species on which Corrêa based his new genus Glycosmis)and cited Roxburgh's plates of them which follow immediately after the plate of Limonia monophylla.
In view of these facts, it appears that the genus Atalantia is, in fact, based on Roxburgh's description and illustration of a plant which he thought was Limonia monophylla L., but which is now known to be another species, very probably Atalantia monophylla DC. Keys to the subgenera and species of Atalantia are presented.
Subgenus Atalantia
Subgenus Euatalantia Swing. in Bailey, Stand. Cycl. Hort. 1:426. 1914.
Type.—Atalantia monophylla DC.
Stamens connate, forming a cylindric
tube, or connate in groups, rarely free; fruits with numerous
well-developed, juicy pulp-vesicles that fill all the space in the fruit
not occupied by the few medium-sized seeds; stipuloid paraphylls
absent.
Seven of the species of Atalantia fall in this subgenus. In general they much resemble the species of the subgenus Rissoa.
1. Atalantia monophylla DC. Prodr. 1:535. 1824. Limonia monophylla Roxb. (non L.) Pl. Corom. 1:59. 1795; (?) Turraea virens Hellen. (non L.) Act. Holm. 9:308. 1788; (?) T. spinosa Willd., in L., Sp. Pl. ed. 4/5. 2:554. 1899 (= T. virens Hellen.); Atalantia spinosa (Willd.) Tan. Jour. Bot. Brit. & For. 68:232. 1930 (name preoccupied!); (?) Mal-naregam, Rheede, Hort. Malab. 4:27. 1679; (?) Malnarega malabarica Raf. Sylv. Tell. Mant. 143. (1838); (?) Atalantia malabarica (Raf.) Tan. Jour. Indian Bot. Soc. 16:233. 1937; Atalantia floribunda Wt. Icon. Pl. Ind. Or. 4:16. 1850. Illus. (?) Rheede, loc. cit. pl. 12; (?) Hellenius, loc. cit. pl. 1, fig. 1; Wight, loc. cit. pl. 1611. 1874; Beddome, Fl. Sylv. Anal. Gen. pl. 7, fig. 5. 1871; Engler, Die Nat. Pflanzenfam. 3(pt. 4):fig. 111,C-D. 1896; ibid. 19a:fig. 150,C-D. 1931; fig. 3-29 this work.
Type.—British India, Coromandel (Roxburgh). Brit. Mus.?
Distribution.—Common in India
(except in Himalayan region and in Bombay State), Ceylon, Burma,
Thailand, Cambodia, Laos, North Vietnam, South Vietnam.
Common name.—Indian atalantia.
A small, much-branched tree with rounded
twigs usually slightly hairy at first, becoming glabrous, with single,
stout, sharp spines, 10-15 or 20 mm long, or unarmed; leaves bright
green above, paler and reticulate-veined below, ovate-lanceolate or
elliptical, variable in size, 3-15 X 2-4 cm (usually 4-8 or 10 X 2.5-3.5
cm), margins entire or slightly undulate, apices obtusely rounded,
often emarginate, bases broadly cuneate, articulated with the wingless
petioles that are 5-10 mm long and 1.5-2 mm wide, flattened above, veins
strongly marked on the under surface, 10-14 on each side, branched,
forming reticulate veinlets and also forked near the margins and
anastomosing; flowers long-pediceled on short racemes (or clustered) in
the axils of the leaves, pedicels 6-15 mm long, finely pubescent or
glabrous, merging into the calyx; calyx more or less irregularly and
deeply 2-cleft, and glabrous or finely pubescent; corolla 4-5-merous,
petals white, glabrous, bluntly rounded at apex, 8-10 mm long; stamens
8-10, united into a tube 6-8 mm long with the anthers borne on the free
tips of the filaments; pistil slender, 6-7 X 1 mm, ending in an abruptly
expanded, 3-4-lobed stigma, 1.2-1.5 mm diam.; style caducous; fruits
globose, 1.5-2 cm diam., yellowish-green when ripe, locules filled with
numerous cuneate, sessile pulp-vesicles which are broad-based and
tapering to a point at their free end, toward the center of fruit; seeds
usually only 1 to a locule; often some of the locules do not develop
seeds.
The most remarkable character of this species (found also in the closely related species A. macrophylla)
is its very curious calyx. This is a hollow, balloon-like
envelope, not articulated with the pedicel and without any sign of
sepals. Soon this undifferentiated envelope splits more or
less irregularly into 2 (rarely 3) lobes, and exposes the corolla,
stamens, and pistil to view.
The nomenclature of this species is in a confused state. Limonia monophylla of Linnaeus has been assumed by almost all taxonomists to be this species. However, Trimen (1893, p. 227) listed L. monophylla L. as a synonym of Atalantia ceylanica, and stated that "the figure of Burmann [1737, pl. 65, fig. l]…appears to represent this rather than A. monophylla…Hermann's specimen…is certainly A. zeylanica [ceylanica]." Airy-Shaw (1939, p. 291) again examined Hermann’s specimen (which is in fact the type specimen of Limonia monophylla L.) in the British Museum and saw no reason to doubt Trimen's findings. Airy-Shaw then showed that A. monophylla was based by De Candolle expressly on "Limonia monophylla Linn." of Roxburgh (1795, vol. 1, pp. 59-60, pl. 83) and that L. monophylla L. was not cited. However, the plant described and figured by Roxburgh was certainly not A. ceylanica and hence was not Limonia monophylla L. Airy-Shaw assumed that Roxburgh's plant from the Coromandel Coast was, in fact, A. monophylla as understood by Hooker (1875, p. 511), and accepted the name A. monophylla
DC. for it. However, Roxburgh described and figured a plant
having a "four-five parted" calyx, a character not found in A. monophylla
as understood by Hooker. That species has, instead of a
normal calyx, a bladder-like continuous membrane covering the flower bud
which, as the bud expands, splits irregularly. Possibly
both Roxburgh and the artist who made the beautiful colored plate of the
Coromandel plant failed to see the irregularly ruptured calyx and,
without careful study, assumed that it was 4- or 5-parted as in most of
the other species of Atalantia and other related
genera. Roxburgh described the leaves as "end-nicked" and
"from two to three inches long, and one or one and a half broad";
nevertheless he published a plate showing a flowering branch with 23
leaves, none of them emarginate at the apex, measuring 1 7/8 to 2 9/16
inches long, and 5/8 to 1 1/16 inches wide, only one leaf slightly
exceeding the minimum width given in the description and more than
three-fourths of them narrower than 1 inch! In view of these
facts, no great importance should be attached to the fact that neither
Roxburgh nor the artist noticed at that time the abnormal splitting of
the calyx, something no botanist had noticed in any species of Atalantia or in any other plant belonging to the orange subfamily.
For the present, it seems best to assume that Roxburgh was describing and figuring the true A. monophylla of Hooker and that A. monophylla DC. is the oldest valid name for it.
Atalantia monophylla has very hard
wood that has been recommended as a substitute for boxwood (Gamble,
1915). The fruits are said to yield a warm oil used in
treating chronic rheumatism by native doctors. One Indian
author (Nadkani) stated that the fruits "make a nice pickle" (Lewis,
1934, p. 80).
When watered frequently, this species makes a luxuriant growth in the greenhouse (see fig. 3-29).
It should be tested as a hedge plant in warm subtropical climates and
in dooryard gardens as an ornamental, since it has dense deep-green
evergreen foliage and bears a great profusion of fragrant flowers and
many small globose yellow fruits. Atalantia monophylla can be grafted on Citrus, and vice versa.
2. Atalantia macrophylla (Oliv.) Kurz. Jour. Asiat. Soc. Bengal 44(2):136. 1875; idem, For. Fl. Burma 1:195. 1877. Atalantia monophylla var. macrophylla Oliv. Jour. Linn. Soc. Bot. 5(Suppl. 2):24. 1861.
Type.—Tenasserim (Helfer). Herb. Bot. Gard., Calcutta (?).
Distribution.—Southern Burma: Tenasserim; Andaman Islands; also Bangka Island and Java (fide Engler).
Common name.—Giant Andaman atalantia.
This species was at first considered to be a subspecies of A. monophylla,
since it has, like that species, the calyx irregularly split, usually
to the base on one side; it differs, however, in having 2 ovules in each
locule of the ovary (A. monophylla usually has only 1), and in
having larger and broader leaves (5-15 X 3.5-6.5 cm). Kurz
(1877, vol. 1, p. 195), who raised A. macrophylla to specific rank, found that it had fruits much larger than those of A. monophylla;
he stated that they are "the size of a wood apple" [which measures
about 3.5-5 cm diam.]. The pedicels of the short racemes are
long (6-15 mm), as in A. monophylla, but are very stout, stiff, and compressed. Atalantia macrophylla
is a small tree, 8-10 m in height, occurring in the Andaman Islands and
Tenasserim. Kurz described it as glabrous in all parts and
almost spineless.
Unfortunately, this very interesting Atalantia
has been very inadequately studied and has never been
figured. Kurz showed clearly that the two species agree in
possessing this remarkable character by putting both A. monophylla and A. macrophylla into the first division of his key to the species of Atalantia,
which reads: "Calyx irregularly lobed, split to the base on one
side." All other Aurantioideae have flower buds with a more
or less regularly (usually 3 to 5-) lobed calyx. This
character, shared in common by the two species, is an almost certain
indication of their very close relationship.
Parkinson reported (1923, p. 108) that
the trunk of this species measures 2 to 3 feet (61 to 91 cm) in girth at
breast height (19.3 to 29.1 cm diam.), an unusual girth for an Atalantia. This Andaman Island form (which Parkinson called A. monophylla) has globose fruits 2.5 cm in diameter; it is common everywhere in deciduous forests.
Engler (1931, p. 328) recognized A. macrophylla as a good species distinct from A. monophylla. Hochreutiner (1904, pp. 50-51) considered the form from Bangka Island as a variety of A. monophylla
differing "in having somewhat larger leaves, less hairy twigs and
especially in having a larger calyx with convex acute lobes; in the
typical A. monophylla the calyx lobes are smaller and
truncate-scarious." A specimen examined in the Botanic
Garden at Buitenzorg (now Bogor), Java, was a round-topped tree, 12 m
high, with a deeply furrowed trunk 1.8 m in circumference (59 cm diam.),
forking at 1 m from the ground and branching profusely at 2 to 3 m from
the ground. No information is given by Hochreutiner
concerning the size of the fruits or the number of ovules in each locule
of the ovary.
Atalantia macrophylla is the only species of the subgenus Atalantia
that is found south of the Asiatic mainland; it seems to have spread
westward to the Andamans and southward to Bangka from extreme southern
Burma, retaining its large size and exceptional girth, but showing
diminished (although still large) fruit size. The typical
form of the species, growing in Tenasserim, has the largest fruits of
any of the Near-Citrus Fruit Trees (included in the genera Citropsis and Atalantia).
3. Atalantia racemosa Wight,15 Hook. Jour. Bot. 1:64, pl. 122. Jan., 1834; A. racemosa Wt. & Arn. Prodr. 1:91. Apr., 1834, nomen semi-nudum. Sclerostylis racemosa Wt. 1838?; S. parvifolia Wt. 1838?; Lampetia racemosa (Wt.) Roem. Syn. Hesper. 1:42. 1846. Illus. Wight, loc. cit. pl. 122; idem, Ill. Ind. Bot. 1:pl. 71. 1838?; idem, Icon. Pl. Ind. Or. 1:pl. 71. 1840; Beddome, Fl. Sylv. Anal. Gen. xlvii, pl. 7. 1871; Talbot, For. Fl. Bomb. Sind. 1:p. 202, fig. 123. 1909; Swingle, Jour. Arnold Arbor. 21:133, pl. 4, fig. 5. 1940.
Type.—Southwestern British India, "Madera…Alpine country" (Wight). Herb. Univ. Glasgow.
Distribution.—Southwestern India: Konkan Coast to Travancore; Ceylon. It is much more common in the Bombay Presidency than A. monophylla, which is there rare (fide Cooke, 1903, p. 187).
Common name.—Bombay atalantia.
This species was described by Hooker
(1875, vol. 1, p. 512) as follows: "Leaflet oblong-elliptic or
ovate-oblong, tip obtuse or 2-lobed, flowers racemed, rarely fascicled,
racemes pubescent or glabrous, calyx 4-lobed, lobes acute or obtuse,
filaments more or less connate, ovary 2-3 celled, ovules 2 collateral.…A
small tree, armed or unarmed, very similar to A. monophylla, but
the flowers, instead of being long-pediceled in short racemes or
fascicles, are shortly-pediceled on racemes sometimes 3 in. long, but at
others almost reduced to corymbs; the leaves are usually larger, and
often broader, though quite small in Wight's figure; the flowers are of
the same size, but often very crowded and the buds very globose, they
are usually 4- but sometimes 3-5-merous, and the filaments are free or
variously united; the ovary is sessile on a small disk.—The great
distinction between these species is in the more or less regularly 4-
(3-5-) lobed calyx of this, the lobes of which are acute or
obtuse. Fruit globose, 3/4 in. [19 mm] diam. One
of Wight's specimens has ovate leaves, cordate at the base.
Wallich’s 6358-E, from Penang (G. Porter), in fruit only, with leaves
cordate at the base, may be this or the following [A. ceylanica], or something different from both."
This species, like A. monophylla, has the stamens fused into a tube. In A. racemosa,
however, the stamens are often fused all the way to the tips into a
cup-like cylinder surrounding the ovary and the anthers are attached
directly to the edge of the cup, whereas in A. monophylla the
tips of the stamens are free and only the bases (about two-thirds to
three-fourths of their length) are fused together into a tube which is
somewhat irregular because the free tips vary in length. The
flower buds of A. racemosa are globose and the calyx differentiates into four or five (rarely three) lobes, whereas in A. monophylla the flower buds are oblong or ovate, pointed at the tips, and the calyx shows
no division into sepals but splits more or less irregularly into two or
three lips often to the base on one side as the bud opens. The fruits are much like those of A. monophylla.
They are globose, about 18 to 20 mm in diameter, and show the three to
five lobes of the persistent calyx. The flesh is composed of
pulp-vesicles.
3a. Atalantia racemosa var. henryi Swing. Jour. Arnold Arbor. 21:127. 1940. Illus. Swingle, loc. cit. pl. 4, figs. 1-4.
Type.—China, Yunnan Province, Szemao, altitude 1,220 m (Henry, No. 12930). in [sic] Herb. Arnold Arbor.; photographs and serial microtome slides, S. and T. Nos. 660-A, 660-B, 660-C, and 660-D (14 slide [sic] with 464 cross sections and 156 longitudinal sections). in [sic] Herb. Natl. Arbor. Paratype: Same collection, in Natl. Herb., sheet No. 459320.
Distribution.—China: Szemao and Chi-li district in southern Yunnan Province near the Indo-Chinese border at altitude 1,100-1,800 m.
Common name.—Henry's atalantia.
A small tree, 4-7 m high, ultimate
branches slender, 2-3 mm diam., soon terete, spineless; leaves glabrous,
lanceolate, short-acuminate at apex, acumen 5-8 X 4-3 mm, tip blunt or
even slightly emarginate, cuneate at base, lateral veins very numerous,
15-30 on each side, not all clearly marked, arising at angles of 50°-70°
with the midrib, margins subentire, petioles 5-10 X 1.2-2 mm, glabrous,
coriaceous, more or less wrinkled, with a deep narrow channel, 0.5-0.8
mm wide on upper side, articulated with the leaf blade; inflorescences
single axillary racemes, 1-2 cm long, with 5-15 flowers borne on slender
pedicels 3-8 mm long, peduncles, pedicels, and calyx pubescent, flower
buds subglobose, 3-4 mm diam., calyx lobes rounded, 1.8-2 mm long, 2-3
mm wide, margins thin and ciliate, petals oblong, rounded at apex,
stamens 8, filaments glabrous or very sparingly short ciliate, cohering
irregularly in groups, sometimes almost to the tips, in other flowers
free almost to base, anthers about 2 mm long, attached near the middle
to the narrowed filament, connective bearing 1 medium-sized oil gland
near tip; disk cup-shaped, 0.5 mm high, 2 mm wide, pistil 3.5-4 mm long,
ovary ovate, 1.5 X 1.5 mm, 4-locular with 2 ovules in each locule, with
1 medium-sized oil gland at top of each locule, style short and thick, 2
mm long (including stigma), 0.7-0.9 mm wide, stigma not clearly
distinguished from the style, about 0.9-1 mm wide, with 4 stylar canals
with 2 medium-sized oil glands in each space between two stylar canals;
fruits subglobose, 1.5-2 mm diam., borne sparingly (1-2?) on each raceme
on pubescent pedicels 3-5 X 1.5-2 mm, with numerous sessile
pulp-vesicles (scanty in ripe fruit from seed pressure?), seeds 1-3,
ovoid-oblong, 12 X 7 mm, monoembryonic.
This variety resembles the typical A. racemosa of
southwestern peninsular India and Ceylon in its racemose flower
clusters, but it has larger leaves, flowers with longer pedicels and
usually with a 4-locular ovary (not 2- or 3-locular) and with the
staminal filaments rarely completely connate into a long tube.
It is remarkable that so far as is known
neither this variety nor the species itself has been found in the vast
region, some 2,700 kilometers across, that separates the Mekong River
valley of southern Yunnan from the Western Ghats in Bombay State,
India. There are many instances of discontinuous
distribution of species or of varieties of a single species belonging to
the tribe Citreae but few are as striking as this one.
4. Atalantia citroides Pierre ex Guill. in Lecomte, Not. Syst. 1:178. 1910. Illus. Guillaumin, loc. cit. p. 176, fig. 8(2); p. 177, fig. 9(3, 4); idem, in Lecomte, Fl. Gén. Indo-Chine 1:pl. 24, figs. C and 5, 6. 1911; fig. 3-30 this work.
Type.—French Indo-China, Cochin China, Mount Dinh (Pierre, No. 4011). Herb. Mus. Hist. Nat., Paris.
Distribution.—South Vietnam: Cochin China; Cambodia.
Common name.—Cochin China atalantia.
Guillaumin's original description of this
species reads, in translation, as follows: "Trees 5-10 m high,
glabrous, spines straight, few, 5 mm long, in the axils of the leaves;
branches grayish. Petioles glabrous, 1 cm long.
Leaves coriaceous, ovate (5-9 X 2-4 cm), entire, attenuate at the base,
attenuate and emarginate at the apex, primary and secondary veins
prominent above and below, oil glands visible only by being pellucid [to
transmitted light]. Flowers very glabrous, in the axils of
the leaves, pedicels glabrous, 1 cm long, with bracts at the base; calyx
cupulate, with 3 or 4 lobes, obtuse at the apex; petals 4, reflexed,
ovate, attenuate at the apex; stamens 10, almost as long as the petals,
more or less equal, connate for 2/3 of their length, anthers ovate,
apiculate; disk annular at the base of the ovary; ovary ovoid-elongate,
terminating in an articulated cylindric style, caducous at maturity,
stigma capitate, locules 3-5, ovules 1-2 [in each locule],
collateral. Fruit very similar to a small orange, 2 cm
diam., pulp made up of succulent vesicles, seeds ellipsoid, about 1 cm
long."
The specimens from Cambodia were said by
Guillaumin to differ from those from Cochin China in having the young
twigs, as well as the peduncles and pedicels of the flower clusters,
slightly pubescent, as shown in his figure C, cited above.
This species has the filaments of the stamens united into a cylindrical tube like A. monophylla and A. racemosa.
The tips of the filaments (about one-third of their length) are free
and the anthers are oval and apiculate, not triangular, as in A. monophylla. The petals are narrowed at the tip, not broadly rounded. The inflorescences resemble those of A. monophylla,
having rather long-pediceled flowers clustered on short inflorescences
in the axils of the leaves. The calyx is much like that of A. racemosa,
with three to four sepals. The fruits resemble small
oranges about 20 mm in diameter, with a rough peel and the flesh formed
of sessile, conical pulp-vesicles. The seeds are ellipsoid,
about 10 mm long.
This species grows to be a medium-sized
tree, 5 to 10 m high, and is probably larger and more vigorous than any
other species of the subgenus Atalantia except A. macrophylla.
Although this species looks much like A. monophylla
and has flowers with similar staminal tubes, it differs greatly in
having a calyx with distinct sepals, unlike the curious balloon-like
calyx of A. monophylla and A. macrophylla that splits irregularly into two or three lobes as the flower bud expands. Tanaka (1930a, p. 163) made this species a synonym of A. monophylla, overlooking this important difference. Guillaumin, who studied A. monophylla, also widely distributed in Indo-China, considered it to be clearly distinct from A. citroides.
5. Atalantia wightii Tan. Bul. Soc. Bot. France 75:714. 1928.
Type.—Nilgiri Hills, Madras, southern British India (Bentham, No. 1531). Herb. Kew.
Distribution.—India; northern Canara, Bombay; Mysore and Madras (fide Tanaka, 1937, p. 234).
Common name.—Nilgiri atalantia.
Tanaka's original description reads,
translated, as follows: "Leaves oblong-ovate, coriaceous, acute at the
tips, rounded at the base, never attenuate; [stipuloid] paraphylls
linear, very short; racemes few-flowered; calyx lobes very narrow and
acute, glandular; stamens free (at length sometimes crowded); style
evenly cylindric; stigma obtuse." A typical specimen
collected in Nilgiri Hills, India (Bentham, No. 1531), preserved in the
Rijks Herbarium at Leiden, Holland, of which Tanaka provided Swingle a
photograph, shows leaves 6-10.5 X 2-4.5 cm (exclusive of petioles),
acute at the tip and rounded or subcuneate at the base, lateral veins
numerous, 15-20 or more pairs arising at a wide angle (60°-70°) with the
midrib, margins entire; petioles very short, 4-6 X 1-2 mm,
wingless. Another specimen of Bentham's type collection (No.
1531), preserved in the herbarium of the British Museum, London, shows
the flowers in axillary racemes or corymbs, with 8-10 or more very small
flowers borne on slender pedicels 4-5 mm long.
A specimen with good flowers and young
fruits in the herbarium of the Arnold Arboretum at Jamaica Plain,
collected by Father Anglade in southern India in the Kodaikanal region,
Pulney [or Pulni] Hills about 75 kilometers northwest of Madura,
identified by Tanaka ("Det. A-382") as Atalantia wightii, has
smaller leaves than the type specimens, blunt at the apex and
emarginate, with the leaf blades 4-7 (or 8?) X 1.5-3.8 cm, with fewer
lateral veins (11-18); petioles 3-6 mm long; flowers small, densely
crowded in axillary racemes, pedicels very slender, 3-4 mm long; calyx
lobes subacute at apex; petals linear, tapering to an acute apex,
5.5-6.5 X 2.5-2.8 mm.
In properly restored material from this
specimen cut into serial sections the floral organs appear as follows:
Stamens 4.5-5 mm long, filaments 2.8-3.2 mm long, 0.1 mm wide at base,
tapering upward, 0.25-0.3 mm thick, cohering in groups near the base,
anthers without an oil gland in the connective; pistil (including disk)
4.5-5 mm long; disk short, shallow-cupulate, 0.5-0.6 mm high, 1.5 mm
wide; ovary ovoid, 2 mm long, 1.6 mm wide, merging into the thick style,
which is about 2 mm long, 1 mm wide, and merges into a stigma of nearly
the same width, slightly 2-lobed for about 0.4-0.5 mm at the top; young
fruits fusiform, 8-9 X 5-5.5 mm (when dry), in restored microtome cross
section 6-7 mm diam., 2-locular with 2 collateral ovules in each
locule, and a few pulp-vesicles developing in the locule walls.
It seems probable that A. wightii is somewhat related to A. simplicifolia and A. roxburghiana. Like these two species, it needs more study of the flower and fruit characters.
6. Atalantia simplicifolia (Roxb.) Engl. Die Nat. Pflanzenfam. 3(4):192. 1896. Amyris simplicifolia Roxb. Fl. Ind. 2:244. 1832; Atalantia caudata Hook. f. Fl. Brit. Ind. 1:513. 1875.
Type.—"Pulo Penang," Malaya? (coll.?). Herb. Brit. Mus., London.
Distribution.—Northeastern India: Khasi Hills; also, fide Tanaka (1930b, p. 232), in [northern] Burma but not yet found in Malaya or even in southern Burma (Tenasserim).
Common name.—Khasi Hills atalantia.
Hooker's original description of A. caudata,
collected by Hooker and Thompson at Churra, altitude 1,220 m [4,000
ft.], Khasi Mountains, northeastern India, now considered a synonym of A. simplicifolia,
reads as follows: "Leaflet elliptic-lanceolate caudate-acuminate with a
broad 2-lobed tip; flowers small in very short glabrous racemes, calyx
very small 4-5 lobed, ovary 2-celled, ovules 2 collateral…A glabrous
unarmed shrub, with slender branches. Leaflets 3-4 in.
[7.5-10 cm], much narrower and more narrowed at each end than in any
congener, margin quite entire, tip sometimes dilated.
Racemes 1/2 in. [13 mm], peduncles and pedicels much more slender than
its congeners. Flowers 1/4-1/3 in. [6-8 mm] diam., white,
fragrant, usually 4-merous, buds rather longer than broad.
Calyx very small. Petals obovate-oblong. Stamens
quite free; anthers ovoid. Ovary sessile on a disk narrower
than itself; stigma subcapitate.—A very distinct species, distributed
as A. Roxburghiana? by T. Thompson and myself."
The type specimen of Roxburgh's Amyris simplicifolia,
preserved in the herbarium of the British Museum, shows the following
characters: leaves elliptical-lanceolate, 6.5-9.5 cm long (excluding
petioles), 2-3.6 cm wide, acuminate at the apex, with an acumen 6-8 X
4-1 mm, the tip blunt and minutely emarginate, cuneate at the base and
narrowed toward the petiole; petioles 5-6 X 11.5 mm with a narrow
(nearly closed?) canal on the upper side, articulated with the blade,
primary veins 10-16 with about as many fainter ones between, arising at
angles of 50°-60° with the midrib; inflorescences axillary, peduncles
1-3 cm long, 0.4-0.6 mm wide, pedicles almost all fallen (about 3.5 mm
long?).
The type specimen of A. caudata preserved in the Kew Herbarium looks very much like-the type of Amyris simplicifolia
except that the leaves are slightly narrower, 2-2.8 cm wide, and have a
longer acumen, 8-11 X 4-2 mm, with a blunter, more deeply emarginate
apex.
This species is still incompletely known
and in particular the flowers and fruits are not adequately
described. It is without doubt related to A. roxburghiana
but seems to be specifically distinct. It has been found so
far only in the Khasi Hills in Assam and in near-by parts of
northwestern Burma, more than 2,500 kilometers distant from the type
locality of A. roxburghiana at Malacca; it has not yet been found in southern Burma (Tenasserim) about 1,800 kilometers distant.
The nomenclature of this species is
confused. The type specimen in the British Museum is
credited to Pulo Penang, but the species has never been found anywhere
near Penang. The original description of Amyris simplicifolia
Roxb. agrees fairly well with the type specimen, but a drawing of the
species, made by Roxburgh and published later by Wight (1840, pl. 72)
under the name Sclerostylis roxburghii, does not agree either
with the description or with the type specimen, as it shows short
petioles not articulated with the blade, the margins of which are
decurrent well down the petiole. It also shows only a few
(five to seven) main lateral veins and about as many more fainter and
shorter ones, whereas the type specimen shows many more veins, both
strong and faint.
If the figure was made from some other
plant, not this species, and if the type specimen came, not from Penang,
but from Assam in northeastern India, or from northwestern Burma, then
undoubtedly the name A. simplicifolia will hold.
7. Atalantia roxburghiana Hook. f. Fl. Brit. Ind. 1:515. 1875.
Type.—Malay Peninsula, Malacca (Griffith). Herb. Bot. Gard., Calcutta?
Distribution.—Malay Peninsula, also Indo-China; fide Tanaka, varieties of this species also occur in Thailand and southeastern China; also, fide Burkill (1931, p. 216), in northern Sumatra.
Common name.—Malayan atalantia.
A sprawling thornless shrub, ultimate
branchlets slender, 1.5-2.5 mm diam., soon terete, glabrous; leaves
large, lanceolate or long-elliptical, tapering toward both ends, but
often acute or shortly subacuminate at apex and sometimes broadly
cuneate or rounded at base, 9-21 cm long (including petiole), 2-4 cm
wide, glabrous, subcoriaceous, with abundant veins visible on both
surfaces, primary veins very abundant, 10-12 stronger ones and as many
fainter ones arising at an angle of 70°-80° with the midrib; petioles
short, 6-10 mm long, 1.3-1.8 mm wide, with a very narrow, almost closed
canal, 0.3-0.7 mm wide, on the upper side, glabrous, articulated with
the leaf blade; flowers not seen; inflorescences (bearing fruits)
axillary, 1-6 cm long, peduncle often simple, bearing pedicels 5-6 mm
long, 0.6-1 mm wide; calyx lobes 4, persistent, glabrous, rounded,
margins thin, sparingly ciliate; fruits subglobose, 1.5-2 cm diam.,
young fruits 2-locular, with abundant sessile, conical pulp-vesicles,
older fruits often nearly full of oblong seeds, 10-12 X 4-6 mm; oil
glands in peel rather sparse and often large, 0.3-1 mm diam.
This seems to be a very well-defined
species, easily recognized by its being spineless and having unusually
long leaves with short petioles, less than one-tenth as long as the
blade, which have a nearly closed canal on the upper side.
It is closely related to A. simplicifolia, which has smaller acuminate or caudate leaves. Two varieties of A. roxburghiana are described below.
The nomenclature of this species and of A. simplicifolia is badly confused, so badly confused that it cannot be settled finally without further study of the type material of both A. roxburghiana and A. simplicifolia. It
is possible that the name here used can be considered as legal since it
was based, in part, on fruiting material that doubtless belongs to the
species as here described. Unfortunately, the original
description was also based on a misleading illustration of Amyris simplicifolia Roxb. which does not agree with the original description of Amyris simplicifolia or with the type specimen of it preserved in the British Museum.
7a. Atalantia roxburghiana var. kwangtungensis (Merr.) Swing. Jour. Arnold Arbor. 21:129. 1940. Atalantia kwangtungensis Merr. Phil. Jour. Sci. 21:496. 1922.
Type.—China, Kwangtung Province, Tung Sing (Ts'oong, No. 1936). Herb. Bur. Sci., Manila.
Distribution.—Known only from the type locality.
Common name.—Kwangtung atalantia.
The original description, in English,
reads as follows: "A glabrous shrub, the branches terete, the branchlets
somewhat compressed, unarmed. Leaves subcoriaceous,
olivaceous, oblong-elliptic, 10 to 14 cm long, 4 to 6 cm wide,
subequally narrowed to the acute base and to the acute or somewhat
obtusely acuminate apex, the upper surfaces slightly shining, the lower
somewhat paler; primary lateral nerves about 14 on each side of the
midrib, prominent on the lower surface, the ultimate reticulations
rather close and distinct on both surfaces, the glands invisible except
by transmitted light; petioles about 5 mm long.
Inflorescences axillary, very short, of solitary or fascicle-like
racemes, the rachis 3 mm long or less. Flowers white, about 6
mm long, their pedicels stout, 1 mm in length; bracteoles ovate,
obtuse, about 1 mm long, the margins ciliate. Calyx lobes 5,
orbicular, rounded, 1.5 to 2 mm wide, the margins slightly
ciliate. Petals 5, 4 to 5 mm long, oblong-elliptic, rounded,
glabrous. Stamens usually 8, the filaments about 3 mm long,
flattened, glabrous, and united for the lower one-half; anthers 1.2 mm
long. Ovary glabrous; style 1 mm long."
This variety differs from the species in
having usually 5-merous flowers (instead of 4-merous) and staminal
filaments cohering from the base for about half their length instead of
being free. Tanaka (1930b, p. 232) referred A. kwangtungensis to A. roxburghiana and Merrill (1931, p. 311) accepted this reduction. In view of the presence of characters in A. kwangtungensis not yet found in typical A. roxburghiana,
it appears possible, even probable, that the southern Chinese form
deserves to be recognized as a variety, as done here, pending further
study of the A. roxburghiana complex of forms.
7b. Atalantia roxburghiana var. kerrii Swing. Jour. Arnold Arbor. 21:129. 1940.
Type.—Thailand, Sam Roi Jawt
(Kerr, No. 10943). Herb. Univ. Aberdeen; photographs,
fragments, and 12 serial microtome cross sections of a fruit, S. and T.
No. 684-A, slides 1-4, in Herb. Natl. Arbor., Washington, D.C.
Distribution.—Known only from the type locality.
Common name.—Kerr's atalantia.
A small tree up to 5 m tall, ultimate
branches at first green and slightly angular, soon brownish, terete and
faintly striate longitudinally; internodes 1.2 cm long; leaves thick and
leathery, broadly oval or elliptical, smaller ones lanceolate, 9-15 cm
long (including the petiole), 3-8 cm wide (usually 6-8 cm), tapering to a
blunt apex, broadly cuneate at base with numerous small oil glands
scattered over the whole surface of the leaf blade but scanty near the
margins which are entire or faintly crenulate and slightly thickened at
the very edge, lateral veins 7-12 pairs, nearly straight or slightly
curved, forked at 5/6-6/7 of the distance to the margin, making angles
of 45°-60° (rarely 65°-70°) with the midrib, with numerous small lateral
veinlets that anastomose; petioles stiff, glabrous, wrinkled, 8-13 mm
long, with a shallow channel on the upper side, 1-2 mm wide, 0.4-0.5 mm
deep; inflorescences axillary, paniculate (?), 2-10 cm long, peduncle
1-2 mm diam., pedicels 5-8 X 1.25-1.8 mm; fruits subglobose, 1.5-1.8 cm
diam., peel covered with large, slightly sunken oil glands, 0.5-0.9 mm
diam., 3-locular, pulp-vesicles numerous, sessile, 3-5 mm long, filling
all the space not occupied by the seeds; seeds ovoid 11.5-12 X 10-11 X
6-8 mm, with a very thin, papery testa (which swells and separates from
the embryo in hot water), monoembryonic.
This remarkable Atalantia has
large, broad, coriaceous leaves; unfortunately it is known only in the
fruiting stage. It differs strikingly in its leaf
characters, not only from A. roxburghiana, but also from the other species of Atalantia
known from the Indo-Chinese region. As the species of this
genus are, most of them, variable in many of their characters, it seems
best to consider this striking form as a variety of A. roxburghiana
Hook. f., not uncommon in the Malay Peninsula and reported from
Indo-China, at least until flowers can be secured for study.
This variety is named in honor of Dr. A. F. G. Kerr, who did so much to
make known the rich flora of Thailand.
Subgenus Rissoa
Subgenus Rissoa (Arn.) Swing. in Bailey, Stand. Cycl. Hort. 1:426. 1914. Rissoa Arn. Nov. Act. Acad. Caes. Leop.-Carol. 18:324. 1836.
Type.—Rissoa ceylanica Arn. = Atalantia ceylanica (Arn.) Oliv.
Stamens free; fruits with the locules
nearly filled with large seeds, with only a few sessile pulp-vesicles;
leaves often accompanied at the base with a pair of small stipuloid
paraphylls.
The species of this subgenus are very like those of the subgenus Atalantia
in general appearance but differ from them in having free stamens, and
nearly dry fruits with large seeds, almost filling the
locules. Only two species of Atalantia (A. ceylanica and A. rotundifolia)
are now known to belong to this subgenus, but probably several others
will be placed here when their fruit structure is better known.
8. Atalantia ceylanica (Arn.) Oliv. Jour. Linn. Soc. Bot. 5(Suppl. 2):25. 1861. Rissoa ceylanica Arn. Nov. Act. Acad. Caes. Leop.-Carol. 18:324. 1836; Limonia monophylla L. Mant. Pl. Alt. 237. 1771; Sclerostylis ceylanica Wt. 1840; S. arnottiana Wt. 1840. Illus. Swingle, in Bailey, Stand. Cycl. Hort. 1:426, fig. 434. 1914 ; fig. 3-31 this work.
Type.—Ceylon (Wight No. ?), Glasgow Univ. Herb. (fide Tanaka, 1930b, p. 232).
Distribution.—Ceylon, low country; southern India.
Common name.—Ceylon atalantia.
This species was described as it occurs
in Ceylon by Trimen (1893, p. 227) as follows: "A much-branched bush,
usually armed with very sharp, stout spines, 1/4-1 in. [6-25 mm] long,
bark smooth, brown, young parts glabrous, l[eaves] very variable, 1
1/4-3 in. [3-7.6 cm long], lanceolate or oval-oblong or somewhat ovate,
rounded at base, emarginate or 2-lobed at apex, entire, coriaceous,
veiny, petiole short, thick, glabrous; fl[owers] 1/2 in. [13 mm diam.]
or rather more, on somewhat slender, glabrous ped[icels], usually
crowded in short, very finely pubescent, corymbose, or racemose cymes
much shorter than the l[eaves], bracts minute; cal[yx] lobes broad,
shallow, often obscure, finely ciliate; pet[als] 4 (rarely 3 or 5),
oval, with a broad claw, obtuse, thick, slightly concave, glandular;
stam[ens] 8, alternate ones longer, quite distinct, fil[aments] flat,
rather wider than anth[ers], anth[ers] cordate-ovate, apiculate; ov[ary]
sessile, smooth, 2-celled, with 2 collateral ovules in each cell; style
short, stout, stigma clavate; berry 1/2-3/4 in. [13-19 mm diam.],
globular-ovoid, 2-4-seeded."
Hooker (1875, p. 511) described it as
follows: "leaflet obtuse, notched or 2-lobed, rarely obtusely acuminate,
flowers very shortly racemed, calyx 4-lobed, filaments free or 2 or 3
of them more or less combined, ovary 2-celled, ovules
2-collateral." He mentioned in the notes that the ovary is
"sunk in the annular disk."
Atalantia ceylanica is remarkable
for its nearly dry fruits, with the very few pulp-vesicles almost
crowded out by the large, plump seeds that almost completely fill the
locules. Small stipuloid paraphylls, 4 to 6 mm long, often
occur singly or in pairs at the base of the petiole. This
species seems to be related to A. guillaumini, from Indo-China,
which apparently has lost its pulp-vesicles and has still larger seeds
that completely fill the locules of the fruit.
9. Atalantia rotundifolia (Thwaites) Tan. Bul. Soc. Bot. France 75:714. 1928. Sclerostylis rotundifolia Thwaites, Enum. Pl. Zeyl. 46. 1858; Atalantia ceylanica var. rotundifolia (Thwaites) Oliv. 1861.
Type.—Ceylon, Muratte (Thwaites,
No. 3295). Herb. Kew; photographs, fragments, and serial
microtome sections of type material, S. and T. Nos. 652-A, 652-B, 652-C,
and 682-D, 17 slides, in Herb. Natl. Arbor., Washington, D.C.
Distribution.—Ceylon: "Montane
zone at about 4,000 ft. [1,220 m] and upwards"; also in Madras, India,
and eastward in Indo-China (Vietnam), Annam and Cochin China (fide Tanaka, 1928b, p. 714).
Common name.—Dwarf Ceylon atalantia.
Thwaites's original description reads
(translated with the addition of the English account) as follows:
"Spineless; leaves rounded or ovate-rounded, retuse, coriaceous;
inflorescences racemose, grouped at the ends of the
branches. A small tree, very much branched,
glabrous. Leaves 0.75-1.75 in. [19-45 mm] long, 0.5-1.4 in.
[12-39 mm] wide; petiole 1-2 lin. [2-4 mm] long. Racemes
axillary and terminal, solitary, or in clusters of 2 or 3,
5-10-flowered, as long as the leaves. Flowers
4-merous. Calyx profoundly 4-lobed; lobes
rounded. Ovary oblong, short-stalked, attenuate into a
cylindric style of equal length ending in a compressed-dilate top with
stigmatic margins; locules 2, 2-ovulate [Latin to here].
"Closely allied to the preceding species [= A. ceylanica],
but distinguished at once by the absence (apparently) of spines, and
the different shape of the leaves. The calyx is deeply
four-lobed, whereas in S. [Atalantia] ceylanica it
is scarcely more than undulated; the style is also more slender in the
present species, and the ovary more decidedly stalked. In
both species the latter organ is surrounded at its base by a free,
glandular annulus."
A photograph of Thwaite's [sic]
type, No. C.P. 3295, in the Rijks Herbarium at Leiden, sent Swingle by
Tanaka, shows that this species has the leaves densely crowded on the
twigs, because of the shortness of the internodes. No spines
can be seen. Many of the leaves are elliptical in shape,
abruptly rounded at the narrow base but usually emarginate (often rather
deeply) at the apex, giving the appearance of an obcordate leaf that
had been greatly compressed laterally. The leaves appear to
be tufted at the ends of the short twigs, where the internodes must be
very short, probably only 4 to 6 mm long in some instances.
The whole appearance of this plant is
reminiscent of the spineless or nearly spineless, short-internoded
mutations of Severinia buxifolia—for example, the brachytic form—and the myrtle-leaved mutation of the sour or Seville orange, Citrus aurantium var. myrtifolia. Possibly this species arose from A. ceylanica as such a brachytic, spineless mutation which in time bred true and persisted at higher altitudes. Atalantia rotundifolia therefore is probably to be considered as a satellite species of A. ceylanica. It is possible that A. rotundifolia will some day be used for hedges or other ornamental purposes in moist subtropical regions.
SPECIES OF UNCERTAIN RELATIONSHIPS
10. Atalantia guillaumini Swing. in Lecomte, Not. Syst. 2:159. 1911. Atalantia disticha Guill. (non Merr.) in Lecomte, Fl. Gén. Indo-Chine 1:673. 1911. Illus. Swingle, loc. cit. 2:162. fig. 1.
Type.—French Indo-China, southern Tonkin, Lang-hé, on Mount Dên (Bon, No. 4047). Herb. Mus. Hist. Nat., Paris.
Distribution.—North Vietnam: known
only from southern Tonkin, from Mount Dên, Mount Nam-cong, Mount
Luong-xa, and Mount Thin-chan (all from collections made by H. Bon.)
Common name.—Tonkin atalantia.
Swingle's original description,
translated, reads as follows: "Leaves ovate-lanceolate, apex obtuse,
base rounded or deltoid with many lateral veins running parallel
[margins entire]; petioles articulated at both ends, not winged, not
[deeply] channeled; calyx persistent, sepals 4-5, subtriangular, with
sparsely ciliate margins; fruits solitary, 2.4-2.8 cm diam., globose,
with 3 or 4 segments, segments 2- (or 1- ?) seeded, destitute of
pulp-vesicles; seeds large, with membranous testa." [Latin
diagnosis to here; continuing, in French, the translation reads:] "A
small tree, 3-4 m high, with spiny, pubescent branches.
Twigs more or less angular when very young, soon becoming rounded and
glabrous. [Fruiting twigs] spineless. Internodes
1-2 cm long. Leaves large, oval or oval-lanceolate, rounded
at the tip and base; the small leaves lanceolate, more or less pointed
at the tip and base; leaf blades 55-85 mm long, 25-60 mm wide, always
clearly distinct from the petiole (which is, moreover, articulated at
the point of junction with the leaf blade), glabrous, without oil glands
except at the margins; lateral veins numerous, 20-30 [sometimes fewer],
parallel and almost straight for 3/4-5/6 of their length, confluent by
anastomosis near the margin; petioles 5-9 mm long, flattened above with
the edges slightly elevated, brown in dry specimens, with many or few
very slender hairs; stipules [stipuloid paraphylls] short, narrow, 2 mm
long, 0.5 mm wide, veinless. Inflorescences few-flowered,
spicate, 3-4 cm long; axillary or else bearing only isolated flowers or a
single fruit in the axils of leaves near the tips of the young twigs;
flowers not seen; fruit pedicels 6-8 mm long, 1.5-2 mm diam.
Calyx persistent, composed of 4-5 distinct sepals that are more or less
triangular, sparsely ciliate on the margins. Fruits
solitary, spherical or slightly pointed, 2.4-2.8 cm diam. with
1-3-fertile segments; seeds 2 in each segment, very large, 12-15 mm
long, 8-9 mm wide, rounded at both ends, more or less angular from
mutual pressure, with a very thin membranous testa; pulp-vesicles
absent, skin glandular and rough, but thin."
Guillaumin (1911, p. 673) described this plant (under the name Atalantia disticha [Blanco]
Merrill) as a "tree 4 m high, spineless," but went on to say,
"branches…with small erect spines," and later on, "petioles…furnished
with 2 erect stipules [stipuloid paraphylls], in the form of spines
reaching 5 mm [in length] or in the form of minute linear leaf blades
[paraphylls] showing a central vein and a few veinlets."
This species much resembles A. ceylanica
(1) in having large fruits filled with very large seeds; (2) in the
general character of the leaves, which have few or no oil glands except
along the margins; and (3) in having frequently one or more paraphylls
more or less like stipules at the base of the petiole, usually more
spinelike than in A. ceylanica. The ripe fruits of A. guillaumini do not show pulp-vesicles, or at least Swingle did not find any in the type specimen. The ripe fruits of A. ceylanica
usually show traces of a few pulp-vesicles, although almost all of them
are crowded out by the very large seeds that almost completely fill the
locules. The still larger seeds of A. guillaumini
may perhaps obliterate all the pulp-vesicles in many of the fruits, or
even in all of them. The study of young fruits of this
species should show whether a few pulp-vesicles are present or whether
they have been completely suppressed. If the latter should
prove to be true, a very interesting and important taxonomic problem
would be raised, since the possession of pulp-vesicles of a special type
is an important character of the genus Atalantia.
Severinia disticha, to which this
species was assigned by Guillaumin (1911, p. 673), is a very different
plant, having small fruits with rudimentary, round, stalkless
pulp-vesicles crowded into the periphery of each locule. A
single seed of Atalantia guillaumini is larger than an entire fruit of Severinia disticha. Severinia disticha has, moreover, the cup-shaped disk enclosing the lower part of the ovary, as in other typical species of Severinia.
11. Atalantia hainanensis Merr. & Chun, ex Swingle, Jour. Arnold Arbor. 21:20. 1940. Illus. Swingle, loc. cit. pl. 4, figs. 3-7.
Type.—China, Hainan Island, Po-Ting (How, No. 72807). Herb. Arnold Arbor, [sic]
Harv. Univ., Cambridge; photographs, fragments, and serial microtome
sections, S. and T. Nos. 261-A, 261-B, 261-C, 12 slides, in Herb. Natl.
Arbor., Washington, D.C. Cotype: Same locality (How,
No. 73976), Herb. Arnold Arbor.; serial microtome sections S. and T.
Nos. 263-A and 263-B, in Herb. Natl. Arbor.
Distribution.—Known also from Yaichow, Hainan Island. Not uncommon, usually in forests near streams at altitudes of 100-640 m.
Common name.—Hainan atalantia.
A small spineless shrub, 1-2 m high;
young twigs slightly angled but soon becoming cylindrical; leaves
simple, persistent, thick and coriaceous, elliptical or broadly
elliptical, slightly acuminate or bluntly pointed at the tip, often
emarginate, cuneate at the base, narrowing gradually into the petiole,
very variable in size, usually 6-15 X 2.5-6 cm, but sometimes as large
as 20 X 8 cm including the petiole, margins entire or faintly undulate;
petiole not articulated with the leaf blade, 5-10 mm long, more or less
pulvinoid, with a channel on the upper side formed by the decurrent leaf
margins; inflorescences axillary, few-branched panicles, short (1-1.5
cm); pedicels slender, 2-3 X 1 mm; flower buds small, 3-3.5 mm long,
2-2.5 mm wide; calyx with 5 triangular lobes, thickened, roughened with
oil glands except at the margins, which are thin and ciliate; petals 5,
white; stamens 10, filaments flattened, connate at the base, free above,
anther with 1 large oil gland in the connective; ovary small, 1.5 X 1
mm, ovoid, with 2 locules, each with 2 collateral ovules, top of ovary
with 1 large oil gland above each locule; style slender, 1.25 X 0.3-0.4
mm, stigma nearly isodiametric with the style, with 2 pairs of large oil
glands; disk cupulate, about 0.35 mm deep, glabrous, completely
surrounding the basal 2/5 of the ovary; fruits (young) ellipsoid, 8-10 X
4-5 mm, peel green, with numerous oil glands, surmounted by the small
persistent style, 1 X 0.6-0.7 mm; seeds 1 (or more?) to a fruit, large,
ellipsoid, about 10 X 7 X 5 mm, monoembryonic (?), cotyledons with
numerous oil glands.
This curious plant, clearly a very
distinct new species, is hard to place in the absence of mature
fruits. It has leaves varying greatly in size (2.5 to 19.5
by 0.8 to 7.5 cm) which have much the same general aspect as those of Severinia buxifolia,
a species it further resembles in having a cupulate disk and a
2-locular ovary with a large oil gland over each locule. One
specimen not considered in the leaf measurements given above (How, No.
73818) from Po-Ting, Hainan, in the herbarium of the Arnold Arboretum,
shows relatively very small leaves, only 2.5 to 5.5 by 0.7 to 1.5 cm,
narrowly elliptical, very blunt-pointed and retuse at the
tip. Young fruits with persistent calyces on this specimen
were, however, almost identical with those of the large-leaved specimens
from the same locality in Hainan. However, serial microtome
sections made of the immature fruits of the cotype (How, No. 73976)
show the locule walls lined not with a clear-cut inner layer of
stalkless subglobose pulp-vesicles but rather with large and
variable-sized oil glands (?), not all in a definite layer but with a
few of them scattered between the much smaller oil glands of the peel
and the inner locule wall. Study of the fruits of this
species at all stages of development may show that these structures have
a merely superficial resemblance to and no true homology with the
primitive pulp-vesicles of Severinia buxifolia and other typical species of Severinia. The typical species of Atalantia
have sessile, broad-based, conical pulp-vesicles growing out from the
dorsal locule walls which with the seeds fill the locules
completely. However, A. ceylanica, the type species of the subgenus Rissoa,
shows in the mature fruit very few pulp-vesicles, perhaps because the
very large seeds almost completely fill the locules. Atalantia hainanensis, like the anomalous A. guillaumini,
of which only the very large, subglobose, fully mature fruits are
known, does not seem to have any pulp-vesicles. These two
anomalous species of Atalantia need critical study at all stages of the developing fruits in order to be certain of their taxonomic placement.
GROUP C. THE TRUE CITRUS FRUIT TREES
This group includes six genera, Fortunella, Eremocitrus, Poncirus, Clymenia, Microcitrus, and Citrus,
all marked by having orange or lemon-like fruits with highly
specialized, slender-stalked, usually more or less fusiform
pulp-vesicles filling all the space in the segments of the fruit not
occupied by the seeds, and also by having at least four times as many
stamens as petals. All the genera have persistent
unifoliolate or simple leaves except the monotypic genus Poncirus, which has trifoliolate, deciduous leaves. Clymenia
differs in having simple leaves borne on short, wingless petioles, with
numerous, nearly straight veins prominent on the lower surface,
somewhat resembling the venation of the leaves of Wenzelia and Monanthocitrus of the subtribe Triphasiinae.
All the genera in this group except Clymenia have fusiform pulp-vesicles borne on very slender stalks, sometimes short, sometimes long. In Clymenia
the pulp-vesicles are subglobose or pyriform in shape, usually having
subglobose apices and being narrowed into somewhat contracted bases; the
bases, however, are never reduced to slender stalks of variable length,
as they are in the pulp-vesicles of the other genera of this
group. All the genera except Clymenia have all, or at
least the majority, of the pulp-vesicles attached to the dorsal walls
of the locules. A few species of Citrus (subgenus Papeda)
have a few or sometimes many pulp-vesicles attached to the radial
walls, but only on the distal portion of these lateral walls nearest the
periphery of the fruit. Clymenia differs from all the species of the subgenus Citrus of the genus Citrus
in that many of the pulp-vesicles, probably a large majority of them,
are attached to the radial walls of the segments and occur on these
walls nearly to the center of the fruit (three-fourths to four-fifths of
the way). Although Clymenia has much simpler pulp-vesicles, without specialized apices, the other fruit characters are very like those of Citrus, to which it is obviously related.
The structure of the pulp-vesicles is of
great taxonomic importance in the classification of the genera of the
subtribe Citrinae. Found only in this subtribe, these unique
structures reach their highest development in group C, the True Citrus
Fruit Trees. In contrast with group B, the Near-Citrus Fruit
Trees, in which the pulp-vesicles are conical in shape, tapering into
more or less acute apices and having broad, sessile bases, the
pulp-vesicles of the True Citrus Fruit Trees are never conical in
outline, but are fusiform, being narrowed at the base (except in Clymenia)
into slender stalks (varying considerably in length in different
pulp-vesicles of the same locule) and into a point at the
apex. In Clymenia the pulp-vesicles are different
from any others occurring in the True Citrus Fruit Trees in being
pyriform and in not being slender-stalked at the base nor having acute
apices.
The pulp-vesicles of all the genera included in this group, with the possible exception of Clymenia
(not yet available for study in the living condition), contain droplets
of oil. These oil droplets are very abundant in the
pulp-vesicles of Poncirus, Microcitrus, and the species of Citrus belonging to the subgenus Papeda, but are fewer in the pulp-vesicles of Fortunella, Eremocitrus, and the species of Citrus belonging to the subgenus Citrus. Similar oil droplets (or even wax particles) occur also in the pulp-vesicles of the Near-Citrus Fruit Trees, Citropsis and Atalantia.
Three genera in group C, Clymenia, Eremocitrus, and Poncirus, are monotypic. Two other genera, Fortunella and Microcitrus,
have four and six species respectively. All five of these
genera have a limited area of distribution much more restricted than
that of Citrus, which is the dominant genus of the subtribe with the largest number of species (sixteen are recognized in this chapter).
The region occupied by the six genera
comprising the True Citrus Fruit Trees is a long, barrel-shaped area
about 9,000 kilometers (5,590 miles) long and 3,200 kilometers (1,990
miles) wide in the center, tapering to about 2,600 kilometers (1,615
miles) at the ends. This barrel-shaped area has its long
axis slanting from the northwest (northeastern India to north-central
China) to the southeast (east-central Australia to New
Caledonia). At its broadest part the area extends from Java
to the eastern shores of the Philippine Islands. If, as some
experts believe, Citrus is native to southern Japan, there would be an extension of the northern corner of this area to include Citrus tachibana. Citrus is native to the whole of the area except in the southernmost corner (northeastern Australia), where it is replaced by Microcitrus and Eremocitrus, and in the extreme northernmost corner (northern China), where it is replaced by Poncirus. Fortunella occurs in southeastern China, where Citrus is probably also native, and Clymenia occurs in the Bismarck Archipelago (the extreme easternmost part of the area), where one species of Citrus is probably also native.
The six genera of group C are all
obviously closely related and all (except the newer, little studied
genus Clymenia) have been grafted on one another and hybridized with one another.
Fortunella resembles Atalantia
(a Near-Citrus Fruit Tree of group B) in having 3 to 5- (rarely 6- or
7-) locular ovaries with only two ovules in each locule, also small
fruits and thick, stiff leaves, but differs in having highly organized,
slender-stalked pulp-vesicles. Eremocitrus has ovary and fruit characters much like Fortunella,
but it has undergone striking xerophytic adaptations that have
culminated in the acquisition of leaves very diverse in structure from
those of the other genera of the True Citrus Fruit Trees. Poncirus
stands alone in group C in having trifoliolate, deciduous leaves and
winter buds well protected by bud scales. It has pleiomerous
ovaries with six to eight locules, with many ovules in each
locule. In these ovarial characters it agrees with Microcitrus and Citrus. Poncirus
undoubtedly represents an ancient offshoot from the True Citrus Fruit
Trees that pushed north into China and in so doing acquired deciduous
leaves and bud scales and developed great resistance to winter
cold. Clymenia is probably the most primitive of all
the genera comprising the True Citrus Fruit Trees. Although
it has fruits (said to be sweet and edible) that appear much like those
of Citrus, it differs widely from Citrus in having more primitive pulp-vesicles and in having leaves that resemble those of the genera Monanthocitrus and Wenzelia of the subtribe Triphasiinae, the Minor Citroid Fruit Trees. Microcitrus is a primitive genus related to Citrus; perhaps some of its species are very like the ancestral species from which Citrus developed.
Of the six genera comprising the True Citrus Fruit Trees, Fortunella, especially the subgenus Protocitrus, is the most simple and primitive of the main branch that ends in Citrus. Microcitrus represents a higher stage of evolution and is still closer to Citrus. Eremocitrus and Poncirus are genera profoundly modified, the one to withstand semiarid climates and the other winter cold. Clymenia is the Cinderella of the group; it shows some affinity with the Papeda subgenus of Citrus and even some relationship to certain of the Primitive Citrus Fruit Trees, namely, Pleiospermium, Limnocitrus, and Burkillanthus, on the basis of which a new theory on the origin of the True Citrus Fruit Trees is possible (see under Clymenia; also under Pleiospermium).
Four of the six genera in group C are
clearly adapted to fit exceptional climatic or soil conditions,
conditions under which Citrus grows poorly or fails completely. Eremocitrus is a pronounced xerophyte, able to grow in semiarid regions in northeastern Australia that are too dry to support Citrus. Microcitrus is semi-xerophytic and can endure long drouths. Poncirus has become deciduous and is able to endure very severe cold in winter, a condition fatal to Citrus and even to Fortunella.
It also has developed well-protected flower buds that form during the
early summer and push into bloom from old twigs the following
spring. Fortunella can withstand long spells of warm
weather in winter or early spring without showing new growth, thereby
escaping all danger of injury from spring frosts, often very injurious
to Citrus. These four genera can grow where no species of Citrus can thrive; perhaps all of them are in fact survivals that escaped destructive competition with Citrus by occupying territory where the latter genus could not live. The other relative of Citrus in this group, Clymenia,
is so little known as yet that it is not possible to state whether it
has any physiological or structural adaptations that permit it to
survive where Citrus would fail. Perhaps, like the
four other genera of limited geographic range, it will on further study
show adaptive structures and physiological peculiarities that will give
it an advantage over Citrus in the regions where it occurs in a wild state.
There is every indication that Eremocitrus, Microcitrus, Poncirus, and Fortunella,
because of their ancient and deeply inbred adaptations to special
climatic and soil conditions, will prove important in breeding new types
of citrus fruits and new rootstocks able to resist disease and able to
endure unfavorable climatic and soil conditions that no Citrus
species can withstand. It is for this reason that every
effort has been made to present as full an account as possible of these
close relatives of Citrus, all of which can very probably be hybridized with Citrus and also with one another.
XXI. Fortunella Swingle
XXI. Fortunella Swingle, Jour. Wash. Acad. Sci. 5:167. 1915.
Type species.—Citrus margarita Lour. = Fortunella margarita (Lour.) Swing.
Distribution.—Southern China, probably now only in cultivation.
Common name.—Kumquat.
Shrubs or small trees; young branches
angular, the older ones rounded; spines borne singly at one side of the
bud in the axils of the leaves, or wanting; leaves 1-foliolate, rather
thick, blunt-pointed or even retuse, acute or rounded at the base, veins
evident above, scarcely showing beneath, lower surface pale green,
densely glandular-dotted; petioles narrowly winged or merely margined,
sometimes not articulated with the leaf blade; flowers borne singly or
in few-flowered clusters in the axils of the leaves, hermaphrodite,
5-merous (rarely 3-, 4-, or 6-merous); flower buds, 8-10 mm long, more
or less angular in cross-section; petals 5 (rarely 4 or 6), white,
acute, 8-12 mm long; stamens 16 or 20, polyadelphous, cohering
irregularly in bundles; filaments broad, but tapering at the tip; pistil
seated on a well-marked cylindrical disk; ovary subglobose, with 3-7
locules, with 2 collateral ovules in each locule; ovary merging
gradually or abruptly into the short style, this usually shorter than
the ovary, sometimes shorter than the stigma; stigma capitate,
symmetrical, cavernous within because of the large, deep-seated oil
glands (1/4-1/5 the diam. of the stigma); fruits small, usually 2-4
times as long as the petiole, ovoid or globose; peel rather thick,
fleshy, aromatic, and sweet flavored, containing large immersed oil
glands; segments 3-7; pulp-vesicles small, fusiform or subglobose,
stalked, containing an acid juice; seeds ovate in outline, smooth;
embryo pistache green, germination with hypogeous cotyledons; first
foliage leaves broadly ovate, subsessile, opposite as in Citrus.
The genus Fortunella resembles Citrus
in the general appearance of the stems, twigs, spines, leaves, flowers,
and fruits and in having the polyadelphous stamens cohering in bundles
and normally four times as numerous as the petals. It
differs from Citrus: (1) in having an isomerous or hypomerous
ovary normally with three to five, rarely six or seven, locules (not
polymerous with 8 to 15 or more locules); (2) in having two collateral
ovules in each locule (not 4 to 12); (3) in having a cavernous stigma
containing a few large, deeply immersed, lysigenous oil glands, usually
in pairs, oval in cross section, with the radial diameter longer, about
one-fourth to one-fifth the diameter of the stigma (in Citrus the homologous oil glands are so much smaller [one-tenth to one-fifteenth the diameter of the stigma in C. sinensis]
that they do not give a cavernous character to the stigma); (4) in
having the under surface of the leaves pale green, nearly veinless, and
with very numerous, small, deep-green glandular dots; (5) in having very
small fruits with acid pulp and a sweet, edible, more or less pulpy
skin; (6) in having small, more or less angular flower buds.
The kumquat bears abundant orange- or
flame-to-orange-colored fruits of small size, often less than an inch in
diameter. Fortunella margarita and F. japonica,
widely cultivated in China and Japan and in all subtropical regions,
have fruits with a relatively thick, fleshy, sweet, edible peel, with
four to seven segments filled with mildly acid pulp. A third
species, with long, slender leaves and long petioles, F. polyandra, commonly cultivated in the Malay Peninsula, has larger globose fruits with a thin peel. A fourth species, F. hindsii,
which grows wild in the mountains of southern China and on the island
of Hong Kong, has very small globose fruits with three to four segments.
The kumquat orange, though described by
early Chinese writers on agriculture, remained virtually unknown to
Europeans until recent times. The kumquat is mentioned in
many early Chinese works and described in some detail by Han Yen-chih
(1923) in his treatise on the oranges written in 1178. Later
works of both Chinese and Japanese authors treat of it fully, often
with fairly good illustrations.
The first vague description of the
kumquat orange in European literature was published by Ferrari in 1646
in his Hesperides and was based on reports made to him by Alvaro
Semedo, a Portuguese Jesuit who lived for twenty-two years in
China. Ferrari's successors, Sterbeeck, Volckamer, Risso and
Poiteau, and other authors of monumental illustrated works on citrus
fruits, have added nothing to our knowledge of the kumquat.
Full descriptions of the round and oval
kumquats were published by Hume (1903, 1909), but not until 1912 was
there a good account of these plants published in Europe, when Trabut
(1912) described them and distinguished them from the so-called
"chinosis" or "chinotto" (Citrus aurantium var. myrtifolia),
with which they had been confused by Volckamer (1708) and many
subsequent European writers. Two years later, Trabut (1914)
published in Algeria a fuller illustrated account of these plants and
gave an explanation of the failure of the kumquat to become known and be
propagated in continental Europe, namely, that seedlings do not thrive
and, furthermore, that viable seed is hard to secure; moreover, he
stated that the kumquat, when grafted on sour or Seville oranges (the
stock generally used), did not succeed at all.
One of the kumquats, F. polyandra,
is native to tropical regions; the other three grow in cool subtropical
or even warm temperate regions. The type species of Fortunella, F. margarita, and the closely related F. japonica not
only are resistant to cold when in a dormant condition but also exhibit
the highest degree of winter dormancy of any of the True Citrus Fruit
Trees. These two species of kumquats can endure fairly warm
weather in winter or early spring lasting for many days or even for some
weeks without starting new growth (Swingle, 1910, 1913e; Swingle and Robinson 1923, p. 229.)
Fortunella approaches Atalantia, and differs strikingly from Citrus, in having only two collateral ovules near the top of each locule (Citrus has 4 to 12 ovules). However, Fortunella differs from Atalantia in having four times as many stamens as petals (instead of twice as many) and agrees with Citrus
in having similar twig, leaf, spine, flower, and fruit
characters. The leaves, however, show very many more oil
glands on the underside than are present in any species of Citrus, often ten times as many. In many superficial fruit characters Fortunella agrees with the Australian desert lime, Eremocitrus glauca.
The seeds are very different, however, and the stem, twig, leaf, and
flower characters are so strikingly different that it is not possible to
regard these genera as being very closely related.
THE SPECIES AND HYBRID PROBLEM IN FORTUNELLA
The species of Fortunella, in
spite of their small number, have been very inadequately studied,
largely because, until recently, only one species was cultivated in
either Europe or the United States and the others were represented only
by scanty herbarium material in a few of the largest herbaria.
The discovery that a small-fruited plant, obviously a kumquat, was masquerading under the name Atalantia hindsii led Swingle to a study of the group, with the result that in 1915 he proposed a new genus, Fortunella, to include all the species of kumquats that had hitherto been placed in Citrus and Atalantia. Important characters were brought to light that separated Fortunella sharply from both Citrus and Atalantia.
Further studies have disclosed the fact that a number of varieties of
kumquats found in cultivation in China and Japan are merely hybrids due
to chance cross-pollinations by insects in village or dooryard
groves. The Meiwa variety (called Chintan in China), at
first considered by Swingle to be a good species (Fortunella crassifolia), and the Changshou kumquat, named as a species (F. obovata)
by Tanaka, are both doubtless mere garden hybrids not entitled to rank
as species. This decision helps greatly in clarifying the
taxonomic status of the genus.
There are also intergeneric hybrids resulting from cross-pollinations between Fortunella and Citrus found
in cultivation in China and neighboring countries. One such
hybrid, the Calamondin, has been erroneously named as a species of Citrus (it was called C. microcarpa by Bunge and C. mitis by Blanco). However, the whole complex intergeneric hybrid problem of Fortunella has been materially clarified by the making of many accurately safeguarded cross-pollinations of Fortunella with Citrus, Poncirus, Microcitrus, and Eremocitrus. This
work, conducted under Swingle's direction in the Agricultural Research
Service, led to the creation of a bewildering group of strange hybrids
that would have been very disturbing to the taxonomist if their origin
were not definitely known. They are discussed below under Fortunella hybrids.
Several species of Fortunella have
developed a degree of resistance to winter cold and at the same time an
even more important physiological peculiarity, namely, a very
pronounced winter dormancy that permits them to pass through weeks of
warm weather without starting growth or flowering. This
quality, possessed in much higher degree by the kumquats than by any
other citrus fruit tree (not excluding the winter-hardy Poncirus),
makes them of prime importance in the breeding of new types of hardy
citrus fruit trees (especially for producing acid citrus fruits) able to
grow in much colder regions than the lemon or lime (both notoriously
deficient in winter dormancy and hence easily pushed into growth by a
few days of untimely warm weather in winter or early spring).
Fortunella hybrids will in all
probability be produced in large numbers in the future.
Their study is likely to prove of great importance in bringing about a
just appreciation of the hybrid problem in the taxonomy as well as in
the breeding of citrus fruit trees. Since Fortunella,
with its few species and its already well-understood intergeneric
hybrids, constitutes a veritable microcosm of the citrus world, it will
doubtless prove of great help in understanding the much more complex and
still only imperfectly studied species and hybrid problems in the genus
Citrus itself. A key to the subgenera and species of Fortunella is presented.
Subgenus Fortunella
Subgenus Eufortunella Swing. in Webber & Batchelor, Citrus Indus. 1:346. 1943.
Ovary with 4-7 locules; fruits more than 1.5 cm diam., with many pulp-vesicles.
1. Fortunella margarita (Lour.) Swing. Jour. Wash. Acad. Sci. 5:170. 1915. Citrus margarita Lour. Fl. Cochinch. 2:467. 1790; C. aurantium [var.] olivaeformis Risso ex Loisel.-Deslong. Nouv. Duhamel 7:95. 1816; C. aurantium var. japonica Hook. f. Curt. Bot. Mag. 3 ser. 30:pl. 6128. 1874; C. aurantium subsp. japonica var. globifera subvar. margarita Engl. Die Nat. Pflanzenfam. 3(4):199. 1896. Illus. Hooker f. loc. cit. pl. 6128 (col.); Siebold & Zuccarini, Fl. Japon. 1:35, pl. 15, fig. 3. 1835; W. G. Smith, Gard. Chron. 2 ser. 2:337, fig. 72. 1874; same figure, ibid. 3 ser. 7:393, fig. 58. 1890; also same figure, redrawn in Gartenflora 31:pl. 1097 (col.). 1882; Swingle, loc. cit. 5:171, fig. 2; idem, in Bailey, Stand. Cycl. Hort. 2:1269, fig. 1563(1); 1270, fig. 1564(1). 1915; Hume, Cult. Citrus Fruits 118, fig. 76. 1926.
Type.—Canton, China, cultivated (coll. by Loureiro, but lost).
Distribution.—Known only in cultivation; doubtless native in southeastern China.
Common name.—Oval kumquat.
Loureiro's original description
(translated from the Latin) reads as follows: "Differs from the species
of Citrus in its ascending, spiny branches, its linear petioles, its 5-locular, oblong fruits.
"Habitat and notes: A tree 4 ft. [1.22 m]
high, branches spiny, ascendant; leaves lanceolate, entire, shining,
few; petioles linear; flowers white with 5 petals, fragrant; peduncles
sparse, few-flowered; fruit oblong-ovate, yellowish-red, glabrous, 8
lines [16 mm] long; 5-locular; peel thin, pulp vesicular, sweet, edible.
"Habitat: Canton, China, not rare. Not seen by me in Cochin China."
Hume (1926) gave the following
description: "Tree dwarf, eight to twelve feet, bushy; young branches
somewhat angled, light green; leaves 1 1/4-3 1/2 X 3/8-1 1/4 inches
[3-8.8 X 1-3 cm], lanceolate, apex obtuse; base acute or obtuse; margins
crenate down about half-way from the apex; veins inconspicuous, surface
dark green, glossy; lower lighter; borne on rather stout, usually very
slightly margined, petioles, 1/4 to 5/8 inch [6-16 mm] in
length. Fruit small, obovate or oblong, 1 1/4-1 3/4 X 3/4-1
3/16 inches [3-4.4 X 1.8-2.5 cm], golden yellow; stem short; calyx
small; rind smooth, aromatic, spicy; oil glands large; juice acid,
sparse; sections usually five; seeds 2 to 5, oval 1/2 inch [13 mm] long,
greenish; cotyledons two, green; season October-January.
The oval kumquat differs from the round
kumquat chiefly in the following respects: (1) the leaves are larger,
more acute at the base, less pallid, and more veiny below; (2) the ovary
has usually four or five (not four to seven) locules; (3) the fruit is
oval, not globose; (4) the style is persistent, not caducous; (5) the
seeds are larger and especially longer, with a rougher
testa. It differs also in being distinctly more vigorous and
attaining a greater height (3 to 4 m); in the somewhat brighter orange
color of its fruits; and especially in the harsher, more biting flavor
of the peel, which evidently contains an ethereal oil more like that of
the common orange than is that of the round kumquat.
The type specimen of Citrus margarita
seems to have been lost, but Loureiro's description is very good and
can apply only to an oval kumquat very similar to the one commonly
cultivated in all the warmer parts of the world.
Robert Fortune, the celebrated explorer
of the tea regions of China, brought back plants of the oval kumquat
from China and delivered them to the Royal Horticultural Society's
Garden in London on May 6, 1846. He stated (1848) that he
had found numerous groves of kumquats thriving to perfection, along with
tea, on the lower hills of Chusan Island (off the coast of Chekiang
Province, near latitude 30°) where the climate is far too cold to permit
the culture of ordinary sweet oranges or mandarins. He
added: "this shows, therefore, that the Kum-quat is of a much hardier
nature than any of the plants belonging to the orange tribe with which
we are acquainted in gardens."
In a later Publication Fortune (1870, p.
50) asserted that the kumquat needs a hot summer, 80° to 100° F and
"will bear without injury 10° to 15° of frost, and perhaps even a lower
temperature."
The oval kumquat reached the United
States by 1850 (see Hume, 1926, 114), but the round kumquat was not
known in either Europe or the United States until near the end of the
nineteenth century.
2. Fortunella japonica (Thunb.) Swing. Jour. Wash. Acad. Sci. 5:171. 1915. Citrus japonica Thunb. Nov. Act. Soc. Sci. Upsal. 3:199. 1780; also Fl. Japon. 292. 1784; C. madurensis Lour. 1790; C. inermis Roxb. 1832; C. aurantium subsp. japonica var. globifera Engl. Die Nat. Pflanzenfam. 3(4):199. 1896. Illus. Thunberg, Icon. Pl. Japon. 2:pl. 5. 1800; Siebold & Zuccarini, Fl. Japon. 1:pl. 15. 1835; Fortune, Jour. Roy. Hort. Soc. London 3:240. 1848; Swingle, loc. cit. 5:168, fig. 1; p. 171, fig. 3; idem, in Bailey, Stand. Cycl. Hort. 2:1269, fig. 1563(2); 1270, fig. 1564(2). 1915; Hume, Cult. Citrus Fruits 116, fig. 74. 1926.
Type.—Japan (in culture) (Thunberg). Herb. Thunberg, Bot. Mus. Uppsala.
Distribution.—Known only in culture, doubtless native in southern China.
Common name.—Round kumquat.
The first fairly complete description of this species, under the name Citrus japonica, was published in 1784 by Thunberg in his Flora japonica;
it reads in translation, as follows: "petiole winged, leaves acute,
shrubby stem. Japanese: Kin Kan, vulgo Fime tats banna,
Kaempf., Am. ex., Fase. V. p. 801. Growing here and there,
often cultivated for its little fruits. Stem shrubby,
compressed-subangulate, erect, glabrous, scarcely a foot
high. Branches and branchlets alternate, compressed-angular,
spinose, glabrous, erect, green. Spines solitary, in the
axils of the leaves, erect divergent. Leaves few, with
winged petioles, ovate, somewhat acute, entire, somewhat concave,
glabrous, dark green above, paler below, erect, spreading, 1 in. [2.5
cm] long, with very minute glands ('poris'). Petioles
winged. 1 line [2 mm] long. Flowers axillary,
often solitary, rarely paired, pediculate, nodding. Pedicels
glabrous, hanging down, 1 line [2 mm] long. Parianth,
1-phyllous, green, glabrous, minute, 5-toothed. Petals 5,
white, oblong, somewhat concave, spreading, somewhat
claw-like. Filaments 19, subulate, compressed, erect, in 5
more or less coherent bundles, connate, forming a cylinder, shorter than
the corolla, nearly equal in length, white. Anthers oblong,
small, yellow. Ovary superior, subglobose,
glabrous. Style solitary, cylindrical, slightly shorter than
the stamens, greenish white. Stigma simple, globose,
yellow, striate, many-locular within. Fruit with fleshy
peel, vesicular pulp, 9-locular [sic], the size of a cherry. Differs from the other species of Citrus
especially in being a very small shrub with minute fruits; thus it can
scarcely be considered as a variety of orange. It resembles Citrus medica
in the axillary flowers, but differs in the winged petioles; it differs
from the orange in the axillary flowers, which are solitary or paired,
never in panicles. Fruit ripens in December and January, is
very sweet, agreeable and edible."
This description was evidently drawn from
a very small plant, perhaps an artificially dwarfed one, such as are
commonly grown in Japan. The very small leaves with axillary
spines, and the fruits "the size of a cherry" strongly indicate that
Thunberg was describing the round kumquat and not the oval kumquat (F. margarita).
His plate of this plant published in 1800 shows a flowering twig with
small leaves and well-developed axillary spines.
Hume (1903 and 1926) described this species as follows:
"Tree similar to Nagami [F. margarita],
except that it is slightly thorny, and has the leaves somewhat smaller
and rounder at the apex. Leaves oval; apex obtuse; margin
crenate halfway down the length; veins slightly more conspicuous than in
Nagami; borne on short rigid, inconspicuously winged petioles, 1/4 to
1/2 in. [6-13 mm] in length. Fruit spherical or somewhat
oblate, 1 to 1 1/4 inches [2.5-3 cm] in diameter; golden yellow, short
stalked; calyx small; rind smooth, thin, spicy to the taste and aromatic
when bruised; oil cells large; pulp sparse; juice acid; sections four
to seven; seeds one to three, small, oval, greenish; cotyledons two,
greenish. Season same as Nagami."
SPECIES OF DOUBTFUL VALIDITY
3. Fortunella polyandra (Ridl.) Tan. Studia Citrol. 6:33. 1933. Atalantia polyandra Ridl. Fl. Malay Penin. 1:359. 1922; Fortunella swinglei Tan. Bul. Soc. Bot. France 75:714. 1928; Citrus polyandra (Ridl.) Burkill, Gard. Bul. Straits Settl. 5:219. 1931; C. swinglei Burkill ex Harms, in Engler, Die Nat. Pflanzenfam. 19a:459. 1931.
Type.—Malay Peninsula (Ridley). Herb. Bot. Gard., Singapore.
Distribution.—Malay Peninsula; Southern China: Hainan Island.
Common name.—Malayan kumquat.
Ridley described this species as follows, under the name Atalantia polyandra:
"Unarmed glabrous bush, branchlets smooth with a ridge decurrent from
the petiole; leaves thinly coriaceous, unifoliolate; leaflets
lanceolate, bluntly acuminate, base narrowed; main nerves slender, about
10 pairs; intermediate nerves nearly as thick, numerous, irregular, all
inarching; [leaflet] 4-6" [10-15 cm] long 1.25-2.75" [3.2-7 cm] wide;
petioles 0.25 to 0.75" [6-19 mm] long, winged above; flowers few,
usually 2 in an axil, pedicels 0.25" [6 mm] long; calyx lobes 5,
ovate-acute, short; petals 5, linear-oblong, blunt, 0.5" [11 mm] long;
stamens 24, connate, in a tube, some shorter than the others, tube
nearly 0.5" [11 mm] long, cylindric; anthers small-ovoid; disc fleshy,
cushion-shaped, forming a gynophore; ovary on the disc, oblong,
glandular, 5-celled; style short, stout; stigma oblong, clubbed,
5-ribbed; fruit globose with numerous large glands 1.75" [4.5 cm]
through (not ripe)."
In his description of Fortunella swinglei,
based on a specimen from the Malay Peninsula, Tanaka stated: "fruits
small, globose, 1.5 cm diam., with 5 locules; peel thin, smooth,
minutely punctate; seeds ovoid, 10 X 15 mm, flattened, apex rounded,
base very acute."
A kumquat collected in May, 1922, by F.
A. McClure (No. C.C.C. 9449) along a woodcutters' path in dense forest
on the south slope of Five Finger Mountain, now in the National
Arboretum Herbarium at Washington (C.P. Or. Herb. No. 7714), was
identified by Tanaka (slip SW-316) as Fortunella swinglei. The
leaves are slender, lanceolate, acuminate, with the very tip
emarginate; the petioles are slender, 12-14 mm long, and very narrowly
winged above. Fruits are not known. It looks
like the wild form from which the Malayan kumquat has been developed by
culture or by hybridization.
This species is as yet inadequately
known. The cultivated form common in the Malay Peninsula,
where it is called limau pagar, or "hedge lime," has much larger fruits than any other species of Fortunella, and likewise a thinner peel. It may possibly prove to be a limequat, i.e., a hybrid of a Fortunella and some variety of Citrus aurantifolia,
but, if so, it is abnormal in having only five locules in the ovary and
only two ovules in each locule. It also has an abnormally
high number of stamens, which may indicate hybridity.
Subgenus Protocitrus
Subgenus Protocitrus Swing. Jour. Wash. Acad. Sci. 5:174. 1915.
This subgenus differs from the subgenus Fortunella:
(1) in having the ovary hypomerous (3- or 4-loculed, not 4- to
7-loculed); (2) in having in mature fruits on the inside of the ovary
wall between the stalks of the pulp-vesicles a number of minute,
wart-like, pale yellow, cellular masses; (3) in having the dissepiments
of the fruit dry, and the peel thin and not very fleshy; (4) in having
shorter, broader, more brachytic flowers; (5) in having leaves with the
veins more prominent on both faces, and less pallid below.
The two most important characters distinguishing the subgenus Protocitrus from the subgenus Fortunella are the few-loculed ovary and the dimorphic emergenzen arising
from the ovary wall of the fruit, viz., ordinary pulp-vesicles and
verruciform tufts of loosely aggregated, more or less colored
cells. These curious organs are analogous to the
short-stalked, clavate slime glands found in Citrus,
but are much more easily seen as they are not intermingled with the
developing pulp-vesicles; they also persist longer, being visible in
half-grown fruits.
4. Fortunella hindsii (Champ.) Swing. Jour. Wash. Acad. Sci. 5:175. 1915. Sclerostylis hindsii Champ. ex Benth. Hook. Jour. Bot. 3:328. 1851; Atalantia hindsii (Champ.) Oliv. ex Benth. 1861. Illus. fig. 3-32.
Type.—Hong Kong (Hinds, no number, coll. 1841). Herb. Kew.
Distribution.—Hong Kong; China: Kwangtung and Chekiang provinces.
Common name.—Hongkong wild kumquat.
A spiny shrub or small tree; twigs
slender, angled when young; leaves oval-elliptical, tapering sharply at
both ends, dark green above and faintly venose, paler and not venose
below; petioles winged, often emerging into the lamina of the leaf
without a separative joint; flowers short, broad, not opening very
widely; pistil very short; style shorter than the ovary; stigma large,
cavernous; ovary with 3 or 4 locules; ovules 2 in a locule; fruits
small, 1-1.5 cm diam., subglobose, bright orange or scarlet-orange when
ripe (the color of a tangerine orange); pulp-vesicles very few, small,
fusiform; seeds thick, oval or ovate in outline, plump, 9-11 X 7-8 X 5-6
mm, pistache green in section.
The Hongkong wild kumquat, Fortunella hindsii, differs from the round kumquat (F. japonica) and the oval kumquat (F. margarita)
in a number of morphological characters, some of them being of decided
taxonomic significance in this group. Longley (1925, p. 347)
found the pollen mother cells of this species to contain eighteen
instead of nine chromosomes as in all other wild-growing species of the
orange subfamily. This plant is in the tetraploid state,
very probably in an autotetraploid state.
Frost (1926, pp. 380-81) found that tetraploid forms of the commonly cultivated species of Citrus
(sweet orange, tangerine and mandarin, grapefruit and lemon) show
"unfavorable tree and fruit characters," such as thickened leaves, lower
vigor, slowness to bloom, coarser rind, and lowered acid content in the
fruits.
Although F. hindsii has long been
known to the Chinese and is not uncommonly cultivated in both China and
Japan, it was not discovered by Europeans until about a century
ago. At first it was not recognized by taxonomic botanists
as being closely related to the other species of kumquats (then placed
in Citrus) but was considered to be a species of Atalantia
(probably because of the small size of the fruit), in spite of the fact
that the stamens are four times as numerous as the petals, whereas in Atalantia the stamens are only twice as numerous as the petals.
The earliest known Chinese reference to Fortunella hindsii is found in the first monograph on citrus fruits ever published in any country, the famous Chü lu
(Orange Monograph) of Han Yen-chih (1923), first published in
1178. In the translation made by Hagerty, the paragraph
about wild kumquats reads as follows: "Chin chü [golden chü orange]. The chin chü grows along the sides of mountain paths; compared with the chin kan
[golden mandarin, the ordinary round kumquat], this fruit is very much
smaller, but is similar in color and form…We sometimes find the tree
bearing enough to fill several pint measures. The pulp
segments of the chin chü cannot be divided. It has but one seed but the taste of its pulp is such that it cannot be eaten. The chin chü
trees are only suitable to be placed in pots on balcony
railings. Many gardeners cultivate and sell them for this
purpose."
Han Yen-chih then went on to say that this little tree is also called shan chin kan
(mountain golden mandarin), meaning wild kumquat, and quoted a song
about it written by Chou Mei-ch'êng, a poet of the Sung dynasty, who
must have written before A.D. 1178, the year Han Yen-chih’s work was
published. A few centuries later, in the Ming dynasty
(1368-1644 A.D.), we find Chinese authors using the name chin tou (golden bean) for this species. This name is found in Min shu
(Records of Fukien), compiled by Ho Chiao-yüan, who lived toward the
end of the fifteenth century. In describing the kinds of
kumquats, he wrote: "there is also the chin tou…growing in the mountain forests; when preserved in honey they are very good."
T’u Pên-tsun (1600?), an author of the Ming dynasty, in an essay, P'ing shih yüeh chih (Calendar of Garden Flowers), named clearly three kinds of kumquats: "the three little friends, the chin tou [or golden bean, Fortunella hindsii], the chin kan [or golden mandarin, F. japonica] and the chin chü [or golden orange, probably F. margarita]." Swingle (1922 and 1929a)
pointed out that this was apparently the first definite recognition of
the fact that these are different kinds of kumquats, now considered to
be three distinct species.
4a. Fortunella hindsii var. chintou Swing. Jour. Arnold Arbor. 21:130. 1940. Illus. fig. 3-33.
Type.—Plant introduced from Japan
and grown in the U.S. Plant Introduction Greenhouse near Glen Dale,
Maryland (C.P.B. 907, F.P.I. No. 71241). Herb. Natl. Arbor.,
Washington, D.C.
Distribution.—Cultivated in the
warmer regions of China and Japan as an ornamental plant.
Doubtless native, or originated under culture in southeastern China.
Common name.—Golden-bean kumquat.
Differs from the parent species, F. hindsii,
in having larger, thinner, somewhat narrower leaves, 3.5-8 X 1.5-2.5
cm, shorter, more slender spines, and larger, slightly depressed,
globose fruits, 12-15 mm in diam., and in having the normal diploid
number of chromosomes (9 in the gametes and 18 in the somatic cells)
instead of twice as many (18 and 36), as the parent species
has. It has also distinctly smaller flowers with petals 5-6 X
2.5-4 mm instead of 6-7 X 4-5 mm, as in the tetraploid species growing
alongside; blunter, much shorter calyx lobes (0.5-0.6 mm long instead of
0.8-1.2 mm, as in the species) and a somewhat narrower and evidently
shorter disk than in the parent species.
This striking dwarf kumquat is probably a
cultivated variety derived from the wild species. It is
unique among the Citrus Fruit Trees in being the diploid state of a normally tetraploid wild species. As is remarked under Citrus, autotetraploid cytonomic states of the commonly cultivated species of Citrus have been found by Frost (1925, 1926, 1938a, 1938b)
to occur not uncommonly in California among seedlings of the sweet
orange, tangerine, mandarin, grapefruit, and lemon. Such
autotetraploid seedlings usually show many or all of the following
characteristics, as compared with the parent species: a tendency to
slower growth, later bearing, and being less floriferous and less
fruitful; also thicker and broader leaves and winged petioles, more
thorny twigs, shorter fruits having thicker rind with larger oil glands,
less juice, and larger, especially longer seeds.
Swingle was able to observe minutely this
cultivated diploid variety during a trip to Japan and China in 1926 and
to bring back living plants with him to this country. This
cultivated form, called by the Chinese Chin-tou (pronounced kindzu
in Japan), meaning "golden bean," has just such characters as would be
expected in a diploid reversion from an autotetraploid
species. It may, however, prove to be a cultivated form of a
species which still persists as a diploid plant.
THE THREE CLASSES OF FORTUNELLA HYBRIDS
The hybrids of Fortunella are many and are both intrageneric (inside the genus) and intergeneric (between Fortunella and
other genera). The hybrid question comes up at every turn
in classifying cultivated citrus fruit trees and is the chief hindrance
to phylogenetic taxonomy of the species of Citrus and Fortunella. It can be given a simpler and at the same time a more comprehensive treatment in a discussion of Fortunella than of Citrus, for the latter has many more species and many more hybrids that are often less easily recognized.
There are at least three distinct classes of Fortunella hybrids. (1) intrageneric hybrids between species of Fortunella; (2) bigeneric hybrids between species of Fortunella and species of Citrus, Poncirus, Microcitrus, or Eremocitrus; and (3) trigeneric hybrids.
INTRAGENERIC HYBRIDS
Two cultivated varieties of kumquats, the
Meiwa (or Chintan) kumquat of China and Japan, widely distributed, and
the Changshou (longevity) kumquat growing in Chekiang and Fukien
provinces of China, are probably to be classed as hybrids between two
species of Fortunella.
Meiwa kumquat.
According to Tanaka (1922, p. 248), the
Meiwa kumquat was so named in Japan because it was introduced from China
during the reign of the Japanese emperor Meiwa (1764-1771).
It is usually called Chintan (golden bullet) in China and is widely
grown in Chekiang Province (Hu, 1934, pp. 22-23).
The Meiwa kumquat is figured and described in Swingle (1915c,
pp. 172-74, fig. 4) and in Hume (1926, p. 117, fig. 117).
The fruits are broadly oval or sometimes subglobose, 25-35 X 25-28 mm,
ordinarily with 7 segments, and usually some of them
seedless. The peel is very thick, nearly twice as thick as
that of either the round or the oval kumquat, and is very sweet and good
flavored. The leaves are also thicker than those of the
common round or oval kumquats and have 4-5 or even more layers of
palisade cells on the upper surface instead of 2 or 3 layers.
The nearly thornless twigs, the often
nearly seedless fruits and the increased thickness of the peel, the
irregularly thickened segment walls, and the thickened leaves with more
layers of palisade cells are in a way an intensification of kumquat
characters that may have resulted from a chance hybridization of the
round and the oval kumquat, or a back-cross with a Fortunella of a Citrus-Fortunella hybrid. The broadly oval shape of the fruits of the Meiwa kumquat is about midway between the oblong fruits of Fortunella margarita and the globose fruits of F. japonica.
Swingle named this variety as a new species, Fortunella crassifolia (1915c,
p. 172), but suggested that it might be of hybrid origin.
He later considered it to be a garden hybrid not entitled to rank as a
species.
Changshou kumquat.
The Changshou (longevity) kumquat is a
dwarf variety commonly grown as a potted plant in China, in the
provinces of Wenchow, Fuchow, Chekiang, and Fukien. A
condensation of Hu's description (1934, p. 24) follows.
Fruits obovate with the tip concave,
about 3 cm long and 3 cm wide, with 8 segments. The peel is
very thin (1.5 mm) and has the same flavor and odor as that of the round
kumquat, F. japonica. The seeds are few (rarely more
than 2 or 3) and polyembryonic. This variety was fully
described by Tanaka (1932c, pp. 151-52, in Japanese; and 1933a,
pp. 38-40, in English). He reported the plant as thornless,
the fruits as "about 3 cm broad, and slightly over 3 cm in height,
obovoid, sometimes nearly globose, but broadest at the apical part; apex
abruptly and rather deeply concave…" The peel is said to be
2.5-3 mm thick, soft, sweet and edible; segments 5-6; the pulp, "juicy,
subacid, refreshing." Seeds sometimes absent but often
rather abundant if present, polyembryonic with more embryos than those
of the Meiwa kumquat.
The dwarf habit, absence of spines, the
frequent seedlessness of the fruits, the concavity at the apex, and the
large number of embryos in the seeds, all point to this as being a
chance hybrid between two species of Fortunella. It was named as a species, F. obovata, by Tanaka (1933a,
p. 38), but specific names for forms suspected of being garden hybrids
or mutations are of doubtful taxonomic validity and should not be
accepted if proof is lacking that the plants are not mere garden
hybrids, propagated only by man's help.
It is probable that other kumquat hybrids
exist in China, since differences in the articulation of the petioles
with the leaf blades are observable in herbarium specimens of Fortunella collected in China.
BIGENERIC HYBRIDS OF FORTUNELLA WITH CITRUS AND PONCIRUS
The citrus experts of the Agricultural
Research Service, using adequate precautions to exclude all stray
pollen, have made a number of bigeneric hybrids of Fortunella.
Apparently, some such hybrids have arisen without human help in the
dooryard or village groves of mixed genera, species, and varieties of
citrus fruit trees. It is probable that some of these chance
seedlings found in the Far East are second-generation kumquat-citrus
hybrids or else backcrosses of an F1 Fortunella X Citrus hybrid on one of the parental species.
Limequats [Citrus aurantifolia X Fortunella sp.].
These hybrids have been described by
Swingle (1914-1917, vol. 4, p. 1882, fig. 2176); by Swingle and Robinson
(1923, pp. 235-38, pls. 4, 5); by Hume (1926, pp. 134-35, fig. 88); and
by Hodgson (see chap. 4, this work).
Most of the named varieties of limequats, Eustis, Lakeland, etc., are hybrids of Fortunella japonica with Citrus aurantifolia
'Mexican,' the round kumquat being the pollen parent.
Another named variety of limequat, the Tavares, has the oval kumquat as
the pollen parent (Citrus aurantifolia 'Mexican' X Fortunella margarita).
Orangequats [Citrus reticulata c. satsuma X (Fortunella japonica X F. margarita 'Meiwa’)].
The orangequat is a complex, artificial,
safeguarded hybrid between the satsuma orange and the Meiwa kumquat (the
latter, the pollen parent, is here considered a hybrid of the round and
the oval kumquat). A named variety of this hybrid, the
Nippon orangequat, was described in Robinson and Savage (1934, p.
11). The fruit is broadly oval or obovate in shape, 3.8 to
5.0 cm in diameter by 5 to 6.3 cm in length, with thick, spongy peel of
mild flavor and with acid pulp.
Citrumquats [Poncirus trifoliata X Fortunella japonica].
The citrumquat proved an exceedingly
difficult hybrid to make. For several years no viable seeds
were obtained. When at last a few were secured, the young
seedlings all died promptly. Finally, in 1909, Swingle found
a few belated "June blooms" on a Poncirus trifoliata tree, nearly all of which set fruit when pollinated with pollen from Fortunella japonica. From
these cross-pollinated trifoliate oranges nearly a hundred seeds
germinated. Many of the seedlings died while still very
young but a few lived and a very few made healthy, vigorous plants that
were obviously hybrid plants and not nucellar seedlings of the female
parent. (See fig. 3-34.)
This hybrid looks much like a citrange in twigs and foliage.
The citrumquat is a combination of two
citrus fruit trees possessing to the highest degree two very different
kinds of hardiness. Poncirus trifoliata is a
deciduous tree able to endure winter temperatures as low as -23° C or
-25° C (-10° F to -13° F), whereas the kumquat, with its highly
developed winter dormancy, is able to withstand long spells of warm
weather in winter or early spring without putting out tender new growth
easily killed by temperatures of even only a few degrees below the
freezing point. This winter dormancy of the kumquat was
noted by Swingle and Robinson (1923, p. 230) in their discussion of
citrangequats.
The extreme difficulty experienced in getting healthy hybrids between Fortunella and Poncirus is
further proof of the remote degree of relationship of these
genera. However, failure to get viable hybrids on the first
trial should not be taken as conclusive proof that such hybrids cannot
be obtained if the parent plants (particularly the seed parent) are in
proper condition when cross-pollinated.
Calamondin (orangequat?) [Citrus reticulata var. austera ? X Fortunella sp. ?].
This Chinese citrus fruit tree, illustrated in figure 3-35,
widely cultivated in the Philippines and also grown in Hawaii and the
United States, is very probably an orangequat that arose in China by
insect cross-pollination of a sour, loose-skinned mandarin orange and a
kumquat, perhaps Fortunella margarita. In the Philippines, it is known under the name Calamonding. This hybrid was described under the name Citrus mitis Blanco by Swingle (1914-1917, vol. 2, p. 784) and by Hume (1926, pp. 133-34, fig. 87) and under the name Citrus microcarpa Bunge by Tanaka (1933b,
p. 184). It was figured in Ochse (1931, pp. 131-32, col.
pl. 50). It is reasonably certain that the Calamondin is a Citrus X Fortunella hybrid and should not be considered as a valid species (see Swingle, 1942, p. 26).
This hybrid has depressed-globose fruits
with a very thin peel, that becomes loose as the fruit ripens, and with
intensely acid pulp. The segments number only seven to
ten. It may possibly turn out to be a back-cross of an F1 Citrus X Fortunella hybrid on Citrus reticulata. This
could probably be determined by experimental hybridization.
This hybrid enters into the parentage of the interesting trigeneric
hybrid, the Altamaha or Glen citrangedin.
Tetraploid Calamondin.
This interesting form of the Calamondin
was discovered in Formosa by N. Nakamura, one of Tanaka's graduate
students. He published (1934) an account of his examination
of a large number of cultivated forms of Citrus, including at the
end of the list several forms of the Calamondin and two other
hybrids. In all, he examined seventy-six species or
cultivated varieties of Citrus and four citrus
hybrids. Only one of these varieties (the one now in
question) showed the tetraploid number of chromosomes. He
called this variety "Shikinari-mikan" and considered it to be a
tetraploid form of the Calamondin. He noted that the pollen
mother cells show 18 bivalent chromosomes in the first division of the
pollen mother cell, and 18 monovalent ones in the second division
(Nakamura, 1934, p. 169, figs. 9, 10). He stated that the
characters of this variety correspond in general to those of the diploid
form of Calamondin, commonly cultivated in Japan; however, the
tetraploid variety has "fruits…larger in size and sweeter,
and…leaves…much thicker than those of the diploid individuals.…Its
pollen grains are also larger than those of the diploid," but more of
them (about 30 per cent) are sterile.
Unlike many tetraploid forms of Citrus, this tetraploid Calamondin grows as vigorously as the diploid form, or even more vigorously.
COMPLEX BIGENERIC HYBRIDS
Procimequat [(Citrus aurantifolia 'Mexican’ X Fortunella japonica) X Fortunella hindsii].
This very interesting complex hybrid,
which has a triploid chromosome number, is the result of a carefully
safeguarded cross-pollination of the Eustis limequat with Fortunella hindsii,
a tetraploid species made by Eugene May and the writer expressly to
obtain a triploid hybrid. Longley (1926, pp. 543-45, fig. 1)
found it to be triploid, with 27 chromosomes in the somatic cells (18
supplied by the male parent, the Hongkong wild kumquat, and nine by the
limequat).
The limequat fruits have from six to nine
segments, as might be expected from a hybrid of the round kumquat (with
four to seven segments) with the Mexican lime (with 10 to 12
segments). The Hongkong wild kumquat fruits have only three
or four segments. The ovaries of the procimequat hybrid
under consideration usually show from four to five segments.
The leaves of these hybrids are small but some of them show fairly vigorous growth (see fig. 3-36). The fruits set abundantly even on small young plants and are small and subglobose, much like those of Fortunella hindsii but
a little larger and a much paler orange in color when ripe.
These fruits are not seedless, as was expected, but produce some
nucellar bud embryos, as do many citranges after the development of the
ovules has been stimulated by pollination. Triploid limes
are usually seedless.
This hybrid is interesting because it throws light on bigeneric Fortunella X Citrus back-crosses such as are possibly represented by the Malayan hedge lime
discussed. The procimequat is in reality intermediate
between a true bigeneric back-cross and a trigeneric hybrid, because Fortunella hindsii belongs to a subgenus, Protocitrus, with many important taxonomic characters separating it from the true Fortunella species placed in the subgenus Fortunella.
The name "procimequat" (given here for convenience) is derived from Pro[to]c[itrus X L]imequat.
TRIGENERIC HYBRIDS OF FORTUNELLA
Several remarkable trigeneric hybrids having Fortunella as
one parent have been made by the citrus experts of the former Bureau of
Plant Industry. These hybrids are of great interest because
of the light they throw on the origin of strange complex hybrids that
arise without human aid in the dooryard citrus groves of China, Japan,
and India.
Citrangequats [Fortunella sp. X (Citrus sinensis X Poncirus trifoliata)].
These were the first trigeneric hybrids
to be produced artificially from definitely known parents.
Swingle succeeded in making this cross in 1909 by using pollen from
Willits and Rusk citranges (Poncirus trifoliata X Citrus sinensis) on properly safeguarded flowers of the oval kumquat (Fortunella margarita) and the round kumquat (F. japonica).
Several of these citrangequats were described and illustrated by
Swingle and Robinson (1923, pp. 230-33, pls. 1, 2, 3). The
Thomasville, Sinton, and Telfair citrangequats, described and figured by
Hume (1926, pp. 40-42, fig. 45), are the best known of these hybrids.
Citrangequats vary greatly in size,
color, flavor, etc. The Thomasville citrangequat has obovoid
fruits borne on long pedicels, 1.5 to 3 cm long and 2 to 2.5 mm in
diameter at the base, but swollen and pulvinoid at the top, 8 to 10 mm,
and permanently curving as the fruit matures until it hangs down, making
an angle of 45° to 90° with the base of the pedicel. This
character is unknown in any of the three parent species and shows how
taxonomically new characters can arise in complex hybrids (see further
discussion under Poncirus hybrids).
Citrangedins [(Fortunella sp. ? X Citrus reticulata var. austera ?) X (Citrus sinensis X Poncirus trifoliata)].
This highly complex trigeneric and
4-specific hybrid is the result of a cross of the Calamondin, itself a
hybrid of Fortunella and Citrus, with the Willits citrange, a hybrid of Poncirus and Citrus.
It bears small, subglobose fruits of a brilliant orange-yellow
color. The fruit was described and figured by Swingle,
Robinson, and Savage (1931, pp. 14-15, pl. 9) and the plant’s extreme
resistance to cold was noted in Swingle, Robinson, and Savage (1932, p.
7). The 4-specific hybrid often shows one- or two-lobed
leaves on young vigorous shoots, and sometimes difoliolate or
trifoliolate leaves. The leaves on fruiting twigs are almost
always unifoliolate and look very like those of a Fortunella-Citrus
hybrid. This hybrid shows clear traces of all three genera
that enter into its parentage but is strikingly different from any
species of Fortunella, Poncirus, or Citrus.
If its parentage were not known, the
Altamaha or Glen citrangedin might even be considered a new genus, as
well as a new species, by those who name "chance seedlings" of obvious
hybrid ancestry as good species!
Faustrimedins [Microcitrus australasica X (Fortunella sp. X Citrus reticulata ‘Calamondin’)].
The faustrimedin is a hybrid of the
Australian finger-lime with the Calamondin, itself a hybrid between the
kumquat and some variety of orange of the mandarin group (Citrus reticulata). It is thus a trigeneric hybrid of Citrus, Fortunella and Microcitrus. The faustrimedin has small leaves much like those of the Australian finger-lime and is hardy like the Calamondin.
This hybrid, first made by Oliver (1911,
p. 40, pl. 1, fig. 2), may be of use in obtaining still more complex
hybrids containing the blood of Eremocitrus or Poncirus.
It is a vigorous grower and shows some promise as a
rootstock. It is easily propagated from
cuttings. The fruits are like finger-limes but are shorter,
nearly seedless, and pleasantly acid.
XXII. Eremocitrus Swingle
XXII. Eremocitrus Swingle, Jour. Agr. Res. 2:86. 1914.
Type species.—Triphasia glauca Lindl. = Eremocitrus glauca (Lindl.) Swing.
Distribution.—Australia: central
and southern Queensland; northern New South Wales. From near
the coast at Broad Sound, Queensland, as far west in scattered colonies
as Long. 142° E. in New South Wales, or possibly Long. 141° E. in
Queensland.
Common name.—Australian desert lime.
Leaves gray-green, thick and leathery
with appressed grayish hairs on both surfaces; spines solitary in the
axils of the leaves, sometimes lacking on older branches; flowers single
or few in the axils of the leaves, 3-5-merous, petals narrowed at the
base, stamens free, 4 times the number of the petals, ovary with 3-5
locules, 2 ovules in each locule, style short; fruit oval or pyriform
with a fleshy peel (as in Citrus), having oil glands, pulp acid,
with stalked subglobose pulp-vesicles, seeds small with hard wrinkled
testa; cotyledons hypogeous, first leaves cataphylls.
This genus is in many ways the best
characterized and most distinct of any of the near relatives of Citrus.
It is the only pronounced xerophytic plant in the whole orange
subfamily. Both leaves and twigs are gray-green, like
sagebrush; the leaves are small, thick, bifacial with palisade
parenchyma on both faces, and covered with a thick cuticle.
The stomata are deeply sunken in pit-like depressions in the surfaces of
both leaves and young twigs. There is a somewhat persistent
sparse coating of thick-walled appressed hairs on the leaves and twigs
not present in any other citrus fruit tree. In the event of
severe drouth, the leaves fall and the gray-green twigs carry on the
very restricted photosynthesis possible under such
conditions. The young plants have greatly reduced linear
leaves that are, in fact, cataphylls. The young seedlings
grow very slowly until an extensive root system is formed; then, if
adequate moisture is found, the stem grows upward as rapidly as that of
any citrus tree and little by little larger leaves are formed until some
may measure 50 to 65 by 10 to 20 mm and nearly 2 mm thick!
The young plants have single sharp, stiff spines in the axils of the
leaves. These are usually 2 to 3 cm long. On
certain particularly vigorous wild trees growing in central New South
Wales, spines of enormous length have been produced. They
are very stout, somewhat up-curved, and reach a length of 6 to 9 cm with
a vertical diameter at the base of 5 to 7 mm and a transverse diameter
of 3 to 4 mm. The flowers are much like those of Microcitrus
but smaller, usually 3- to 5-merous with six to ten entirely free
stamens with slender filaments. The ovary has three to five
locules with two ovules in each locale, a character not found in any
other True Citrus Fruit Tree except Fortunella! The
fruit is small, subglobose, ovoid or obovoid, 15 to 25 by 12 to 15
mm. The subglobose pulp-vesicles have short, slender stalks
and are loosely aggregated, not cohering as tightly to each other as in
the common citrus fruits. The seeds are small and contain
only a single embryo.
This remarkable xerophytic citrus fruit
tree grows wild in central and northern New South Wales and in
southeastern Queensland. In New South Wales, it is sometimes
found in semiarid regions even as far west as the Mootwingee Range
(Lat. 31° 45' S., Long. 142° 10' E.), about 80 miles northeast of Broken
Hill in extreme western New South Wales.
Eremocitrus glauca (Lindl.) Swing. Jour. Agr. Res. 2:88. 1914. Triphasia glauca Lindl. in Mitchell, Jour. Exped. Trop. Austr. 353. 1848; Atalantia glauca (Lindl.) Benth. Fl. Austr. 1:370. 1870. Illus. Fairchild, U.S. Dept. Agr. Yearbook 1911:pl. 45, fig. 1. 1912; Swingle, loc. cit. text figs. 1-7; idem, in Engler, Die Nat. Pflanzenfam. 19a:332, fig. 153,a-o. 1931; Maiden, Forest Fl. N. S. Wales 7:245, pl. 248, figs. A-H. 1921; Flanders, Calif. Citrog. 17:278, 6 unnumbered half-tone text pls. 1932; fig. 3-37 this work.
Type.—Australia, Queensland,
Dublin County, near junction of Maranoa and Merivale rivers (Mitchell,
1846). Kew, Brit. Mus., and Gray Herb. (Swingle, 1914b, p. 90).
Distribution.—Australia: central
and southern Queensland; northern New South Wales. From the
Burdekin River (Lat. 20° S.) in northeastern Queensland to the coast at
Broad Sound (Lat. 23° S.), thence south along Long. 152° E. to the New
England district in northeastern New South Wales, thence southwest to
Dubbo in central New South Wales (Lat. 32° 20' S., Long. 149° 35' E.),
thence westward (rather common) to Long. 147° E., or even 146° E., and
also occurring in scattered groups much farther west in the hills in the
semiarid region as far as Long. 142° E. in New South Wales and possibly
Long. 142° E. or even 141° E. in Queensland.
Common name.—Australian desert lime.
The typical form of this species as it
occurs in southeastern Queensland, Australia, is a small tree or a large
shrub, sometimes growing as a thorny bush only a few feet in
height. F. M. Bailey described it as "a rigid glaucous shrub
of 2 or 3 ft., often armed with straight or incurved axillary spurs of
1/2 in. or under…" However, Flanders (1932, p. 278) figured a
giant tree at Chinchilla, Layton County, in Queensland, some 130 miles
west-northwest of Brisbane, that had a single trunk, about 25 feet in
height and measuring 20 inches in diameter at 2 feet above the
ground. The round crown was about 28 feet
across. Such a tree undoubtedly grew where its roots had
access to ground water.
The leaves are gray-green, very thick and
leathery, usually oblong, linear- or elongate-obcuneate, obtuse at the
apex, often emarginate, 25-40 X 4-10 mm. Both surfaces show
appressed, grayish hairs and have a thick cuticle with sunken
stomata. The leaves are more or less paraheliotropic (on the
edge to the light) and have no clearly defined upper and lower surfaces
(Swingle, 1914b, figs. 5, 6, 7). Flowers very small,
3-5 mm long and 5-8 or 10 mm across, borne singly or in groups of 2 or 3
in the axils of the leaves on slender pedicels, 4-6 mm long, flowers
3-5-merous, with 4 (sometimes 3) times as many stamens as petals,
stamens short, filaments slender, 4-5 mm long (sometimes slightly united
at the base according to Bailey); pistil short, 3-4 mm long, ovary
ovate with 3-5 locules; fruits subglobose or obovoid, 7-12 X 8-10 mm,
pulp-vesicles small, subglobose, on short, slender stalks and nearly
free from one another; seeds small, oval, 5-6 X 3-4 X 2.5-3 mm, testa
rough, monoembryonic. Young plants growing in the greenhouse
at Washington, D.C., had very slender, straight or slightly upcurved
thorns, 25-35 mm long but only 1-1.5 mm diam.; young trees growing out
of doors at Riverside and Indio, California, show much stouter spines,
2-3 mm diam., but seldom as long as 35 mm. The twigs on
young plants are usually very slender, 1-2 mm diam., and for several
years bear very narrow, slender leaves or cataphylls, 18-30 X 1-2 mm,
and make very slow growth; as soon as an extensive root system has
developed, the young tree grows upward rapidly, producing larger leaves
on slightly stouter twigs, 2-3 mm diam., that often show only very short
spines or none.
The trees growing at Indio under
irrigation began to flower and set fruit when they were 12-15 feet high
and about 8-10 years old. At that age the branches were
comparatively short and the trees compact with but little spread (at 20
years of age one tree was 20-22 feet high and the top spread 12-16
feet). The flowers appear very abundantly in March, and by
late May or early June the fruits begin to drop while still green or
slightly yellowish-green. The fruits are juicy,
thin-skinned, and rather pleasantly acid. Two forms occur:
one strain has subglobose fruits, the other obovoid or short-ovoid
fruits.
The Australian desert lime, Eremocitrus glauca, is a pronounced xerophyte, the only one found thus far in the orange subfamily (fig. 3-38).
It is able to withstand severe drouth and hot dry winds.
Under such conditions the leaves fall off and the leafless gray-green
twigs (resembling those of the smoke tree, Dalea spinosa, and the
paloverdes, common in the arid regions of the southwestern United
States and northern Mexico) carry on photosynthesis on a reduced
scale. The seedling develops an enormous root system before
making vigorous aerial growth and developing full-sized leaves (young
seedlings bear only very slender cataphylls). The roots are able to
endure rather high concentrations of salts in the soil moisture and are
much less susceptible to boron poisoning than are those of Citrus. When
in a dormant condition this species is able to withstand, without
injury, temperatures of ten or more degrees below zero Fahrenheit (-24° C
or lower). It probably possesses a higher zero point of
growth and, in consequence, a greater dormancy in late winter and early
spring than Citrus. It apparently ranks next to, but
does not equal, the kumquats in possessing both winter dormancy and
resistance to cold.
There is good reason to believe that Eremocitrus has spread slowly
westward in northeastern Australia over a long period of time, probably
some 20 million years or more, during which time this plant has become
adapted to withstand a semiarid climate and to grow in soils having an
appreciable saline content in the soil moisture. Trees of Eremocitrus glauca have
been found growing wild in northeastern Australia up to east longitude
142° 10’, a distance inland of 800 to 960 kilometers (500 to 600
miles). The western half of this range falls in a region
classed as "Dry Steppe" by the Australian experts Andrews and Maze
(1933), whose maps show that Eremocitrus grows wild as far west
as the climatic zone which according to their designation has an average
of from six to eight arid months. Their No. 8 line
(indicating eight arid months in the year), which separates the steppe
climate from the desert climate in Australia, runs through the
westernmost limit of the range of Eremocitrus. Convincing proof of the drought resistance of Eremocitrus
is found in certain thrifty groves of the desert lime growing in
regions in Australia where salt bushes thrive and where trees of some
other species die during prolonged drought before the Eremocitrus trees show even slight injury.16
In spite of years of effort on the part
of several generous Australian cooperators, the attempt to obtain seed
from the Eremocitrus trees growing wild in the drier parts of
Queensland and New South Wales proved unsuccessful up to
1941. A few mature fruits were found west of longitude 148°,
but they contained no viable seeds. Fortunately, in
December, 1941, C. T. White collected ripe fruits of Eremocitrus glauca
containing viable seeds in the vicinity of Charleville, Queensland, in
the Warrego River Valley (Long. 147° 40' to 145° 30' E.).
The trees from which the seeds were obtained were growing under semiarid
conditions. These seeds germinated and the seedlings grew
well in the greenhouses of the U.S. Department of Agriculture near
Washington, D.C. The complete absence of seed in fruit of
this species growing in its natural habitat is apparently the rule,
according to information supplied in a letter dated December 2, 1964 to
Dr. J. R. Furr, U.S. Date and Citrus Station, Indio, California, from E.
C. Levitt, New South Wales Department of Agriculture, Sidney,
Australia. As recently as 1964, the E. glauca trees
growing at the U.S. Date and Citrus Station have been the source of seed
supplied to Australian citrus specialists for their studies on the
suitability of E. glauca as a rootstock and its tolerance to salinity.
Eremocitrus glauca can serve as a rootstock for Citrus aurantium and other species of Citrus; when used for the sour orange excellent growth was obtained in the Washington greenhouses. Eremocitrus also grafts readily on Citrus.
BIGENERIC AND TRIGENERIC HYBRIDS OF EREMOCITRUS
Eremocitrus trees growing near a collection of Citrus species and hybrids in the U.S. Date and Citrus Station at Indio, California, have fruited heavily (fig. 3-39).
A small percentage of the seedlings from them have proved to be
hybrids. In all, several score of such hybrids have been
found and many of them propagated from cuttings (fig. 3-40). Efforts to pollinate castrated and bagged Eremocitrus flowers from Citrus or other genera have not so far succeeded, probably because of the great profusion of blossoms produced by Eremocitrus, of which doubtless only one in a hundred or so set fruit.
Swingle believed that two kinds of Eremocitrus hybrids are easily distinguished: bigeneric hybrids, in which a Citrus species is the pollen parent, and trigeneric hybrids, which have a citrange for the pollen parent.
In the revision of this chapter, the junior author has maintained Swingle's classification of bigeneric and trigeneric
hybrids. However, it should be noted that Dr. J. R. Furr,
U.S. Date and Citrus Station, Indio, California, has reservations
concerning such classification. In a letter to Dr. Walter
Reuther, the editor of this volume, dated June 7, 1965, he stated:
I have some reservations regarding
Swingle's supposed eremolemon, eremorange, eremoradias, etc.
As well as I can remember the seedlings of the old E. glauca
tree that used to grow at the U.S. Date and Citrus Station looked about
the same after the Meyer lemon tree growing very close to it was removed
as they did before its removal; but there were grapefruit trees nearby
all of the time, so it is possible that we were getting E. glauca X grapefruit hybrids.
I have been puzzled by the E. glauca seedlings I have grown. Usually there is a mixture of types in the open-pollinated seedlings grown from our E. glauca trees
ranging from vigorous, upright plants with lanceolate leaves to very
small, weak plants with thorny branches and only vestigial
leaves. The weak ones usually die in the flats before they
are large enough to plant in the field. I supposed that the
weak thorny plants were possibly selfed E. glauca seedlings and that the vigorous ones were probably hybrids with citrus. We have never caged a tree of E. glauca to see if it will produce any seed without cross-pollination. One year I did pollinate flowers of E. glauca with several different kinds of citrus. On different branches of E. glauca, flowers were pollinated by hand with pollen from sweet orange, pummelo, rough lemon, and Shekwasha. No seed [sic]
were obtained from flowers pollinated by pummelo. Seedlings
that appear to be hybrids were obtained from the other crosses; that
is, the seedlings were highly variable and there seemed to be family
differences between the different lots of seedlings of supposedly
different pollen parents. In these supposed crosses, the E. glauca flowers
were not emasculated; the pollen was just daubed on the stigmas of many
open flowers, which may have been self-pollinated at the same time.
I think Swingle was probably right in supposing that many of the E. glauca seedlings grown from the original old E. glauca
specimen at the U.S. Date and Citrus Station were hybrids. I
doubt that he had adequate evidence to justify his assumption that he
could tell what the hybrids were. Bees do work E. glauca vigorously, and if trees of E. glauca and the citrus species were quite close together, I should think there would be some cross-pollination.
At the same time, Dr. Furr notes in
closing his discussion that: "Swingle probably grew or had grown by his
subordinates more seedlings of E. glauca than anyone ever grew before or since his day."
BIGENERIC HYBRIDS
Eremolemons [Eremocitrus glauca X Citrus limon 'Meyer lemon'].
All the bigeneric hybrids between Eremocitrus and Citrus have unifoliolate leaves, intermediate in size between the two parental species but thin and bifacial like those of Citrus.
Many years ago, all citrus trees except a Meyer lemon were removed from
the vicinity of a fruitful Australian desert lime in the Coachella
Valley at the U.S. Date and Citrus Station. Desert
conditions produced about one-fifth hybrids, probably with Meyer lemons
as the pollen parent. They grew vigorously, and when 8 to 10
feet high flowered and fruited rather abundantly, producing subglobose,
slightly oblate, yellowish fruits, 18 to 25 mm in diameter, which have
five or six segments and usually one to three seeds. Upon
germination, these seeds grew rapidly and produced plants which looked
exactly like the original hybrid. Doubtless these eremolemon
seeds contained only nucellar-bud embryos which reproduced the mother F1
hybrid exactly. This Coachella eremolemon, as it is called,
has a high tolerance for boron and doubtless a greater tolerance for
salinity in the soil moisture than any species of Citrus. Its seedlings are remarkably uniform, grow rapidly when young, take Citrus buds readily, and have taproots like the Citrus rootstock used by nurserymen.
Eremoranges [Eremocitrus glauca X Citrus sinensis].
Doubtless some of the many hybrids grown from seed from the Eremocitrus trees at the U.S. Date and Citrus Station were of this parentage.
Eremoradias [Eremocitrus glauca X Citrus aurantium].
Perhaps a few hybrids developed at the
U.S. Date and Citrus Station were of this parentage, as a sour orange
tree grew only a dozen yards away from one of the most fruitful trees of
Eremocitrus glauca.
TRIGENERIC HYBRIIDS
Citrangeremos [Eremocitrus glauca X (Poncirus trifoliata X Citrus sinensis)].
These hybrids showed trifoliolate or
difoliolate leaves and usually also some unifoliolate
leaves. They were undoubtedly the result of the pollination
of Eremocitrus flowers from a row of citrange trees (Savage,
Morton, and Rustic) growing nearby in the U.S. Date and Citrus Station
at Indio. Many of these hybrids had very narrow leaflets,
which perhaps was the reason they were weak and of slow growth.
Both the bigeneric and the trigeneric hybrids of Eremocitrus
are very unlike any known citrus fruit trees, but evidently they cannot
properly be named as new genera and new species. If it
proves possible to cross-pollinate successfully a citrangeremo [= Eremocitrus X (Poncirus X Citrus)] with another trigeneric hybrid already existing, the faustrimedin [= Microcitrus X (Fortunella X Citrus)], no fewer than five genera of True Citrus Fruit Trees will have been combined in the resulting hybrid, viz., Citrus, Fortunella, Microcitrus, Eremocitrus, and Poncirus!
Naturally such ultra-complex hybrids, if obtained, would not be
recognized by taxonomists as constituting true genera or true species.
XXIII. Poncirus Raf.
XXIII. Poncirus Raf. Sylva Tellur. Mant. 143. 1838. Pseudaegle Miq. Ann. Mus. Bot. Lugd.-Bat. 2:83. 1865-1866.
Type species (monotype).—Citrus trifoliata L. = Poncirus trifoliata (L.) Raf.
Distribution.—Central and northern China; widely cultivated.
Common name.—Trifoliate orange.
Small trees with single, stout, axillary
spines and palmately 3-foliolate, deciduous leaves, twigs dimorphic; (a) normal twigs with internodes as long or longer than the petioles, (b)
foliage spurs, which develop from dormant buds on twigs of previous
year, with extremely short internodes (less than 0.5 mm long) bearing
1-5 normal foliage leaves but no spines; flowers developing singly at
the nodes in spring from scale-covered flower buds formed early in the
previous summer on last year's twigs that lose their leaves during the
winter; sepals 5, petals 5, long, slender, spathulate or clawed; stamens
4 or more times the number of petals, with free, glabrous, slender
filaments; ovary subglobose, pubescent, seated on a short, shallow,
cup-shaped disk broader than the ovary; ovary with 6-8 (sometimes fewer
or more), usually 7 locules; ovules 4-8 in 2 rows in each locule; style
short, thick, merging into the slightly clavate stigma; fruits globose
or short-pyriform, subsessile, 3-5 cm diam., finely pubescent, with
lemon-yellow, soft, orange-like peel with abundant oil glands;
pulp-vesicles elongate-conical, slender-stalked, bearing scattered,
secretory, hair-like organs, and filled with acid pulp containing
numerous droplets of acrid oil (or oily wax) in the center; seeds oval,
plump, often with several supernumerary nucellar embryos; germination
hypogeous; young seedlings developing at first bract-like cataphylls,
then intermediate forms that soon merge into normal 3-foliolate leaves.
This remarkable genus, although evidently closely related to Citrus, Fortunella, Microcitrus, and Eremocitrus,
has many strikingly aberrant characters. In the first
place, it differs from all the other True Citrus Fruit Trees, which are
found in only tropical or subtropical regions, in having penetrated far
into the temperate zone in northeastern Asia; in so doing it has become a
deciduous tree with small leaf buds and larger scale-covered flower
buds (formed in early summer) that pass the winter on the leafless
terminal twigs and open before (and sometimes with) the leaves early in
the following spring. The trifoliolate leaves are doubtless a
survival of the foliage of some remote ancestral plant. All
the other True Citrus Fruit Trees have unifoliolate leaves (except Clymenia, which has simple leaves) that persist on the tree for two or more years and cannot endure severe cold.
The pith of the stem shows transverse
plates composed of thick-walled cells, not as yet found in any other
genus related to Citrus (see Swingle, 1909). The
pulp-vesicles carry scattered hair-like organs that bear at their
expanded tips a number of rounded, thick-walled cells with numerous
small, oblique fissures. These organs secrete a viscous
fluid that allows the pulp-vesicles to slip past one
another. These organs are unknown in any other genus of the
orange subfamily. The immature fruits contain ponciridin, a
glucoside analogous to hesperidin, but not found in Citrus.
Poncirus hybridizes freely with Citrus.
Such hybrids, called citranges, citrandarins, etc., are usually
ovule-sterile but occasionally produce some fertile pollen
grains. Poncirus has also been hybridized (after overcoming many difficulties) with Fortunella and citranges have been hybridized with Eremocitrus.
The pulp-vesicles of Poncirus
contain numerous droplets of oil. Penzig (1887, pp. 161-62)
discovered these inclusions and found that some of these oil globules
were semisolid and more or less brittle. Oil droplets are
also found in the pulp-vesicles of Citrus, being very abundant in the species of Citrus which belong to the subgenus Papeda.
Poncirus is not easy to place in a phylogenetic series along with Citrus
and other related genera arranged so as to show the course of
evolutionary progress. Doubtless many "missing links"
between it and the ancestors of Citrus have perished, leaving Poncirus as perhaps the most isolated and aberrant genus of all the True Citrus Fruit Trees.
Poncirus trifoliata (L.) Raf. Sylva Tellur. Mant. 143. 1838. Citrus trifoliata L. Sp. Pl. ed. 2. 1101. 1763; C. trifolia Thunb. Fl. Japon. 294. 1784; C. triptera André (non Desf.), Rev. Hort. 57:518. 1885; Aegle ? sepiaria DC. 1824; Pseudaegle sepiaria (DC.) Miq. Ann. Mus. Bot. Lugd.-Bat. 2:83. 1865-1866; Limonia ? trichocarpa Hance, 1882. Illus. Kaempfer, Amoen. Ext. 5:801. 1712; Hooker, Bot. Mag. pl. 6513. 1880; Nicholson, Gard. Chron. 3 ser. 27:269. 1900; Penzig, Studi Bot. Sugli Agrumi, Atl., pls. 13, 14. 1887; André, Rev. Hort., 57:pl. facing p. 516 (col.). 1885; Georgeson, Amer. Gard. 12:525. 1891; Swingle, U.S. Dept. Agr. Bur. Pl. Ind. Circ. 46:figs. 1-6. 1909; idem, in Bailey, Stand. Cycl. Hort. 5:2751, 2752, figs. 3123-25. 1916; Tillson & Bamford, Amer. Jour. Bot. 25:784, figs. 29-33. 1938; fig. 3-41 this work.
Type.—Based on Kaempfer's description and plate.
Distribution.—Central and northern China; widely cultivated in Japan, Europe, and North America.
Common name.—Trifoliate orange.
Small, much-branched tree, twigs of rapid
growth, strongly angled, becoming cylindrical with age; spines single,
stout, straight, sharp, oval in cross section (vertical axis longer);
twigs dimorphic: (a) normal twigs with internodes 1-5 or even 8
cm long with a single leaf at each node, in the axil of which is a bud
and often a stout spine; (b) foliage spurs, arising from the nodes of the twigs of the previous year's growth (but above
the spine and 5-8 mm above the scar of the fallen leaf in the axil of
which it was laid down as a bud), with 1-5 (usually 2-4) excessively
short nodes (less than 0.5 mm long), each bearing a normal foliage leaf
but no spine, tipped with a bud 1-2 mm wide, covered with green,
overlapping bud scales with more or less ciliate margins (such foliage
spurs may persist for two [or more?] years developing 2-4 or more leaves
each year); leaves palmately 3-foliolate; terminal leaflet 3-6 X
1.5-2.5 cm, shallowly crenulate, serrate above the middle, cuneate at
the base, midrib slightly raised on both surfaces and gradually
expanding below near the base for 2 or 3 mm into a pulvinoid swelling
entirely included in the leaf blade and not free except at the extreme
base (i.e., no petiolule), lateral leaflets 2.5-5 X 1-2 cm, sessile,
lower half wider, petioles 1-2.5 cm, wing 2-3 mm at broadest part,
tapering to the base; leaflets on leaf spurs very similar but with
petioles slightly longer in proportion to the length of the middle
leaflet; spines stout, straight, acute, 1-6 cm long, 3-10 mm diam. at
base, 2-4 mm diam. in the middle, oval in cross section (vertical diam.
nearly twice the transverse in the lower third of the spine); flowers
produced in spring on twigs of previous year's growth from subglobose
flower buds, with bud scales usually ciliate on the margins, flowers
single, nearly sessile, 5- (rarely 4- or 6-) merous; calyx composed of 5
small, nearly free, ovate, cucullate, persistent sepals, 8-10 X 3-4 mm;
corolla composed of 5 white petals, 18-30 X 8-15 mm, flat when fully
open, subspathulate, often narrowed into a claw at the base, soon
deciduous; stamens 20 or more (up to 60); filaments free, unequal in
length, slender, tapering gradually toward the tips; ovary subglobose, 2
mm diam., pubescent, with 6-8 (usually 7) locules; ovules numerous, in 2
rows in each locule; style short, 1-1.5 mm long, merging into a rather
large, subclavate stigma; fruits almost sessile, globose, ovoid or
slightly pyriform (sometimes with a blunt nipple at the tip set in a
depression surrounded by a ring-shaped furrow), 3-5 cm diam., dull
lemon-colored and fragrant when ripe, finely and densely pubescent, peel
5-10 mm thick, with numerous oil glands, rather rough; seeds ovoid,
plump, very numerous, leaving very little space for the pulp, which is
composed of slender-stalked, narrow, elongate-fusiform pulp-vesicles
filled with very acid juice and having a slender column of numerous
small droplets of acrid oil in the center. The pulp-vesicles
bearing hair-like appendages, expanded at the tips; these usually show
scattered thick-walled cells having numerous small slanting fissures,
which secrete a viscous fluid.
The
trifoliolate orange shows surprisingly few variations considering that
it has been grown in China for thousands of years and in Japan since at
least the eighth century. Palmately 4- or 5-foliolate leaves
are seen very rarely on old trees. In the parks of
Washington, D.C., a small-flowered form occurs that has shorter petals
than the normal form and these are occasionally seen bearing the
rudiments of anthers on their margins. In other words, such
flowers show partial staminody of the petals.
The curious dwarfed variety with very narrow, almost threadlike leaflets, called hiryô in Japan, where it is cultivated as a dwarf potted tree, is described below.
The Comte de Castillon (1877, p. 73, figs. 11, 12) reproduced Japanese
figures and gave Latin varietal names to two other sports of this
species grown in Japan—the variety microcarpa, which has minute fruits, and the variety punctata, which has leaves dotted with golden-yellow spots, called in Japan sunago
or "gold-dust" trifoliate orange. These interesting garden
sports probably do not merit recognition in taxonomic botany as
varieties.
In spite of the variations mentioned above, it is probable that Poncirus trifoliata,
of all the True Citrus Fruit Trees, is the most stable of the species
that have been cultivated for long periods by man. This may
perhaps be due to the fact that this aberrant genus is not very closely
related to the other genera in the group; if it crosses with them, the
resulting hybrids (citranges, etc.) are almost always
sterile. Thanks to this circumstance P. trifoliata has preserved its nature with little change in spite of long culture.
The trifoliate orange has been used very
extensively in Japan and somewhat less so in the United States as a
rootstock for the satsuma and other cultivated citrus fruit
trees. It is also used occasionally for hedges (Swingle,
1911) and is commonly grown as an ornamental in Asia, Europe, and North
America, especially in regions that are too cold to permit the culture
of ordinary citrus fruit trees out of doors.
Poncirus trifoliata has been crossed with Citrus making
hybrids called citranges that have proved valuable as vigorous, hardy,
disease-resistant rootstocks for ordinary citrus fruit trees.
The Chinese have for centuries used the
dried fruits of the trifoliate orange in their medical
practice. Apparently both the immature fruit, called chih-shih,and the fully ripe, sliced, and dried fruits, called chih-k'o, are utilized, but for different purposes.
Poncirus trifoliata var. monstrosa (T. Ito) Swing. in Bailey, Stand. Cycl. Hort. 5:2952. 1916. Citrus trifoliata var. monstrosa T. Ito, Encycl. Jap. (Nippon Hyakka Daijiten) 2:1056. 1909.
Type.—Cultivated in Japan.
Common name.—Flying-dragon trifoliate orange.
Tokutaro Ito's original diagnosis in English reads as follows: "Citrus trifoliata var. monstrosa T.
Ito, nov. var. Branches and spines crooked and curved,
leaves very slender." A very dwarf variety, with tortuous
slender branches with curved spines; the leaves are very small with the
leaflets often reduced to linear filaments on which the oil glands
appear as node-like thickenings.
In Japan this curious monstrosity, called hiryô, or flying dragon, is esteemed for culture as a dwarf potted plant.
PONCIRUS HYBRIDS
Citranges [Poncirus trifoliata X Citrus sinensis].
As the genus Poncirus is
monotypic, all its hybrids are intergeneric, i.e., either bigeneric or
trigeneric. The first adequately safeguarded hybrids of Poncirus and Citrus
were made by Swingle in 1897. These hybrids, called
citranges, showed such striking differences, even between sister hybrids
grown from a single fruit, that a number of them (Rusk, Willits,
Morton, Coleman, Savage, Rustic, and Saunders) were named, described,
and illustrated. (See Swingle and Webber, 1898, p. 400, text
fig. 13; Webber and Swingle, 1905, pp. 223-35, pls. 10-16, text figs.
12 and 13; Webber, 1907, pp. 329-36, pls. 17-20; Swingle, 1910, pp.
36-41, pls. 1-2; idem, 1913e, pp. 83-87, pls. on pp. 84, 86, 88, 90, 92; idem, 1913f, pp. 382-86, figs. 1-4; idem, 1927b, pp. 19-21.) Several named varieties of citranges are described by Hodgson in this work.
Citrumelos [Poncirus trifoliata X Citrus paradisi].
Citrumelos are very similar to
citranges. At least one of them, the Sacaton, produces large
numbers of seeds containing only nucellar embryos and consequently
yields identical F1 seedlings in great numbers, like the Troyer citrange (see Hodgson, this work). The Sacaton is a promising rootstock.
Citrandarins [Poncirus trifoliata X Citrus reticulata].
Citrandarins are much like citranges
except that the mandarin orange parent greatly reduces the amount of
bitter oil found in droplets inside the pulp-vesicles. In
citranges this oil usually makes the fruit too bitter to eat.
Citremons [Poncirus trifoliata X Citrus limon].
Many of these hybrids show abnormally small leaves in germinating and soon die (Swingle, 1913f);
others are broad-leaved. One, the Highgrove, is a very fast
grower with fruits like a lemon but rougher and more seedy.
Citradias [Poncirus trifoliata X Citrus aurantium].
These hybrids greatly resemble citranges
but seem to be even more vigorous and cold-resistant. The
Brownell citradia (fig. 3-42)
grows vigorously and fruits freely in northern Alabama at Tuscaloosa
(Lat. 33° 12’ N.). It makes a good stock for the commonly
cultivated citrus fruits.
Citrumquats [Poncirus trifoliata X Fortunella japonica, or F. margarita].
These hybrids are very difficult to make,
germinate badly, and nearly all die while still very small.
Nevertheless, a very few of them have been obtained that grow
vigorously (see under Fortunella).
SECOND-GENERATION CITRANGES
Segentranges [(Poncirus trifoliata X Citrus sinensis) F2].
Almost all Poncirus X Citrus
hybrids are completely ovule-sterile, although almost all of them
produce a little fertile pollen. Only two of the many
citranges that have been studied (the Phelps and the Sanford) regularly
produce true second-generation seedlings, all of which show
extraordinary variability. Some of the seedlings are almost
like the one or the other parent species, and all degrees of
intermediates occur. In the experimental plantings these
hybrids have been called segentranges, for convenience, but this name
covers such a range of forms as to be of little practical value (see
Swingle, 1910, p. 37, pls. 3, 4 [showing Sanford citrange F2 seedlings]; Swingle, 1927b, p. 20; and Hodgson, this work).
BACK-CROSSES OF PONCIRUS HYBRIDS ON THE PARENT SPECIES
Citrangors [Citrange X Citrus sinensis].
These hybrids are often very like the
sweet orange in leaf characters; the fruits have not as yet been
studied. The orange-like seedlings resemble also the
orange-like second-generation seedlings of the fertile citrange
varieties. Some of the citrangors show trifoliolate leaves
and look much like citranges (see Swingle, 1910, p. 36, pls. 7, 8).
Cicitranges [Citrange X Poncirus trifoliata].
These hybrids often look much like Poncirus trifoliata in both leaf and fruit characters. The fruits are often more juicy and contain fewer seeds than those of P. trifoliata
but are always more or less bitter from the droplets of acrid oil in
the pulp-vesicles. All the cicitranges are trifoliolate, but
some are citrange-like with broad lateral leaflets.
TRIGENERIC PONCIRUS HYBRIDS
Citrangequats [Citrange X Fortunella sp.].
These vigorous and variable hybrids are discussed in this chapter under Fortunella.
Citrangedins [Citrange X (Fortunella X Citrus) 'Calamondin’].
A remarkable hybrid of this parentage is discussed in this chapter under Fortunella.
Citrangeremos [Citrange X Eremocitrus glauca].
These hybrids are discussed in this chapter under Eremocitrus.
CITRANGES AND OTHER PONCIRUS HYBRIDS IN DOORYARD AND VILLAGE GROVES
All Poncirus hybrids are marked by
their trifoliolate or difoliolate leaves and hence are easily
recognized even when the seedlings are too young to have flowered or
fruited. There is every reason to expect that similar
spontaneous hybrids due to cross-pollination by insects between Citrus and Poncirus
should be found; as a matter of fact, such hybrids do occur in China,
Indo-China, and Malaya. Also it is to be expected that
intergeneric hybrids between Poncirus and widely different species of Citrus should
exist; in fact, these are found in the homeland of citrus fruits, in
southeastern Asia, Japan, and throughout the Monsoon region.
Swingle saw in the dooryard gardens in
China trifoliolate citrange trees and also trifoliolate, difoliolate,
and unifoliolate forms that were probably citrangors; other forms,
obviously Poncirus hybrids, have been found in China and in
Indo-China. It is therefore to be expected that back-crosses
and second-generation seedlings, as well as complex 3-parental hybrids,
should occur not uncommonly as "chance seedlings" in dooryard citrus
gardens in the Far East.
Fortunately the vast amount of carefully
safeguarded hybridization work that has been done in the United States
on the True Citrus Fruit Trees has shown what types of hybrids may be
expected to occur, and as a matter of fact do occur, when mixed
plantings of species of Citrus, Fortunella, and Poncirus
in dooryard or village groves are cross-pollinated by insects (which
visit the flowers with great assiduity because of their abundant supply
of nectar). Chance seedlings are almost certain to arise
from seeds dropped in such dooryard or village groves and their chance
seedlings can and do persist, flower and fruit. If the fruit
is valued, such hybrids are propagated by grafting and a new cultivated
variety is born.
Knowing, as we do, the exact origin of the remarkable hybrids of Poncirus listed above, as well as of the many other, even more complicated, hybrids listed under Fortunella and under Eremocitrus,
we are able to appreciate how unscientific it would be if "new species"
(and even the "new genera" that would be needed in some instances) were
created to include these hybrids (whether they arose artificially by
human design or spontaneously through insect pollination), thus giving
them the same taxonomic status as genuine species that arise in nature
by slow evolutionary processes.
XXIV. Clymenia Swingle
XXIV. Clymenia Swingle, Jour. Arnold Arbor. 20:251. 1939.
Type species (monotype).—Citrus polyandra Tan. = Clymenia polyandra (Tan.) Swing.
Distribution.—Known only from the type locality near Namatanai in northern New Ireland, Bismarck Archipelago, northeast of New Guinea.
Common name.—Clymenia.
This genus is allied to Citrus; it
differs in having (1) subsessile pulp-vesicles (somewhat narrowed at
the base but not borne on slender stalks) attached in great numbers to
the lateral segment walls for 3/4 the distance from the peel to the
axis; (2) very numerous stamens (50-100) with free, slender filaments;
(3) ovary with a very short, stout style (less than 1/2 the length of
the ovary); and (4) leaves with very short petioles, from 1/10 to 1/20
the length of the leaf blade, with which they are not
articulated. The flowers arise singly in the leaf axils and
are borne on straight, rather stout pedicels, slightly longer than the
petioles of the subtending leaves; calyx persistent, 5-lobed, lobes
reflexed at apex in dried material, suberect at sinuses, thick and
coriaceous, wrinkled without, glabrous within; corolla 5-merous, petals
imbricate, dotted with numerous small oil glands; stamens very numerous
(10-20 times as many as the petals), filaments free, slender, anthers
oblong; ovary ovoid with 14-16 locules, ovules several in each locule;
style very short (about half the length of the ovary); stigma capitate;
disk broader than the ovary, about half as long; fruit ovoid, size of a
small orange, skin thin, orange-like, dotted with oil glands;
pulp-vesicles attached in part to the dorsal, but principally to the
side walls of the segments; seeds very numerous, small, subglobose or
oval, glabrous, embryo green. Small trees, branches
spineless, twigs subangular when young, then cylindrical; leaves thin,
smooth, with numerous subparallel lateral veins, acuminate-caudate at
apex, cuneate at base, tapering into the very short petiole, furrowed
above, and not articulated with the leaf blade.
This remarkable new genus (of which only
one species is known) is in its general aspect so much like Citrus
that it was at first mistaken for a sweet lime. It bears
sweetish edible fruits about the size and shape of a sweet lime (5 to 6
by 7 to 8 cm), even to a short nipple at the apex. The ripe
fruits are yellow in color, again like sweet limes. However,
Clymenia differs very widely from Citrus in many
important taxonomic characters and is undoubtedly a distinct new
genus. It is especially noteworthy in having a type of
pulp-vesicle not known in any other citrus fruit.
The type of this genus, Citrus polyandra,
was described in Latin rather fully by Tanaka in all its characters
except the detailed structure of the pulp-vesicles and the manner of
their attachment in great numbers to the side walls of the fruit
segments. The pulp-vesicles are short, plump, blunt, oval or
subglobose, sessile or very short-stalked. What is also
important from a taxonomic standpoint is that these pulp-vesicles are
attached in very large numbers all along the side walls of the segments,
nearly to the inner angle touching the central axis of the
fruit. The leaves of Clymenia are very unlike those of any other True Citrus Fruit Tree (Citrus, Microcitrus, Eremocitrus, Fortunella,or Poncirus) and strongly resemble those of Monanthocitrus, a genus of the Minor Citroid Fruit Trees described from New Guinea by Tanaka. Monanthocitrus
has, however, a much simpler floral organization with only twice as
many stamens as petals, instead of 10 to 20 times as many, as in Clymenia. The fruits of Clymenia
are about the size of a small orange. The greatly enlarged
disk bearing very numerous stamens is unique in the orange subfamily.
Clymenia polyandra (Tan.) Swing. Jour. Arnold Arbor [sic] 20:253. 1939. Citrus polyandra Tan. Studia Citrol. 2:158, 163. 1928; Citrus medica subsp. limonum var. limetta Lauterb. (non "[Risso] Engl.") Bot. Jahrb. 55:264. 1918. Illus. Tillson & Bamford, Amer. Jour. Bot. 25:786, figs. 34-36. 1938; Swingle, loc. cit. pl. 1, figs. 1-5; fig. 3-43 this work.
Type.—Bismarck Archipelago, New
Ireland, Namatanai, Nukonoku (Peekel, No. 408). Herb. Bot.
Mus., Berlin-Dahlem. Fragments of type: Herb. Natl. Arbor., Washington, D.C., sheet No. 46011. Topotype:
New Ireland, Buratamtabai, Namatanai (C. S. Gee, 5/6/37, with the help
of Father Peekel!), Herb. Natl. Arbor, Washington, D.C., sheet No.
46010.
Distribution.—Bismarck Archipelago: known only from the vicinity of Namatanai, New Ireland.17
Common name.—Clymenia.
Tanaka's original description (in Latin)
may be translated about as follows: "Branches triangular, glabrous,
without spines; leaves oblong, caudate-acuminate, abruptly narrowed at
the base, irregularly serrate; petioles very short, not articulated
[with the leaf blade], and not winged, but furrowed [on the upper side];
flowers single in the axils of the leaves, with rather long, somewhat
thick, pedicels; calyx saucer-shaped, obscurely toothed; stamens up to
100, free, arising in many rows outside the disk; filaments linear;
anthers oblong; ovary ellipsoid; style thick, very short; stigma
capitate, somewhat pentagonal; fruit oblong, somewhat lemon-shaped, with
an inconspicuous mammilla at the tip; peel thin, segments numerous;
pulp vesicular, yellow, rather sweet; pulp-vesicles short, blunt, very
numerous; seeds obovoid, superposed."
The twigs are spineless and the leaves
are very peculiar, being elliptical, acuminate at both ends, with the
base merging into a very short, slender, wingless petiole which is not
articulated or in any way marked off from the blade. The
flowers are produced singly in the axils of the leaves, petals short and
broad (7 X 7 mm); stamens very numerous (50-100) in many whorls, with
short filaments (5 mm), pistils shorter than the stamens, ovary ovoid,
with a broadly rounded tip not merging into the style, ovary with 14-16
locules, style short (only half as long as the ovary), with capitate
stigma; fruit lemon-shaped, 4.5 X 6-7 cm, with a short nipple at the
apex; pulp sweet; seeds numerous, superposed, polyembryonic.
Tanaka deserves the credit for having
first noticed the great divergence of this plant in many of its
essential taxonomic characters from any other of the known True Citrus
Fruit Trees. However, he considered it to be a hybrid of Citrus macroptera and C. medica, which is said by Lauterbach to be "commonly planted at the [European ?] stations."
After studying Citrus macroptera and other members of the subgenus Papeda and observing the hybrids between them and species of the subgenus Citrus that are common in the Philippines, Swingle became convinced that a hybrid such as Tanaka thought his Citrus polyandra to be (Citrus macroptera X C. medica)
could not possibly show a wingless petiole, even though one supposed
parent, the citron, has an almost completely wingless petiole, because
the other supposed parent, C. macroptera, has a very long, very broadly winged petiole (certainly the largest petiole to be found in Citrus).
The extraordinarily close resemblance of the leaves and petioles of this species to those of Monanthocitrus convinced Swingle that this plant was an entirely new type of citrus fruit tree, possibly having descended from a remote ancestral species common also to Monanthocitrus. Swingle thereupon published Clymenia as a new genus to include this plant (see fig. 3-43).
This species, called a-mulis by the natives in the village of Namatanai in New Ireland, is cultivated for its sweet fruits.
XXV. Microcitrus Swingle
XXV. Microcitrus Swingle, Jour. Wash. Acad. Sci. 5:570. 1915.
Type.—Citrus australasica F. Muell. = Microcitrus australasica (F. Muell.) Swing.
Distribution.—Of the 6 known species, 5 are found in eastern Australia (Queensland and northern New South Wales) and the other (M. warburgiana) in southeastern New Guinea.
Common name.—Australian wild lime.
Twigs minutely puberulous; leaves
dimorphic, those on young seedlings greatly reduced cataphylls gradually
merging into small, linear or elongate-elliptical leaves and finally
into the normal foliage of the species; mature leaves more or less
coriaceous, strongly veined, glabrous except in midrib near base;
petioles short, wingless, finely pubescent, especially on the upper
flattened side; spines slender, acute, single (or in pairs in M. inodora and M. maideniana)
in the axils of the leaves; flowers small, 4-5-merous, stamens entirely
free, ovary with 4-8 locules; ovules several, 4-8 or more in each
locule; fruits round-ovoid or cylindric; pulp-vesicles noncoherent,
slender-stalked, subglobose or ovoid (except in M. australis, in
which they are elongate-fusiform, tapering above), filled with acid pulp
having minute droplets of acrid oil aggregated along the axis; seeds
small, ovate in outline; cotyledons hypogeous in germination.
This genus is obviously related to Citrus,
from which it differs, however, in having dimorphic foliage, free
stamens, an ovary with four to six (or eight) locules, and more or less
coriaceous, strongly veined leaves. Moreover, it is related
to the highly specialized genus Eremocitrus, which also has dimorphic foliage and free stamens. Eremocitrus, however, differs from Microcitrus in
always having thick, coriaceous leaves with thick cuticle palisade
tissue and stomata on both faces and an ovary with only three to five
locules having only two ovules in each locule.
The six known species of Microcitrus
are the result of millions of years of slow evolution from a primitive
ancestral type. From this ancestral type arose the genus Eremocitrus, with marked xerophytic adaptations and two ovules in each locule of the ovary, and the genus Microcitrus, with more numerous ovules in each locule.
This ancestral type probably resembled somewhat M. warburgiana,
the New Guinea species, which has small leaves and small, nearly
spherical fruits. From such an ancestral form, one line of
evolution produced the so-called native orange, round lime, or Dooja (M. australis), that grows to a large tree and has subglobose fruits much larger than those of M. warburgiana, with long, slender, pointed, more or less twisted pulp-vesicles; another line of evolution culminated in M. inodora and M. maideniana,
highly specialized forms showing adaptations to tropical rain forests,
with large leaves and paired spines; a third line of evolution led to
the small-leaved, somewhat xerophytic species M. australasica and M. garrowayi, both with long-ovoid or very elongate-cylindric fruits.
These remarkable citrus
fruits are extremely interesting, in that they show how evolution has
proceeded in regions isolated as Australia and New Guinea have been
during the last twenty or thirty million years since they were cut off
from all other land masses.18 The evolution of other citrus fruits is not so easily followed, since Citrus, Fortunella, and Poncirus did not originate in regions that were geographically isolated in definitely dated geologic eras. A key to the species of Microcitrus is presented.
1. Microcitrus australasica (F. Muell.) Swing. Jour. Wash. Acad. Sci. 5:572. 1915. Citrus australasica F. Muell. Fragm. Phytogr. Austr. 1:26. 1858. Illus. G. W. Oliver, U.S. Dept. Agr. Bur. Pl. Ind. Bul. 202:pl. 15, figs. 5, 6; pl. 2, fig. 1. 1911; F. M. Bailey, Comprehen. Cat. Queensl. Pl. 84, fig. 63. 1913; Swingle, loc. cit., figs. 1-4; fig. 3-44, E this work.
Type.—Moreton Bay, Queensland (F. von Mueller). Present location (?).
Distribution.—Australia: coastal regions, southern Queensland; northern New South Wales.
Common name.—Australian finger-lime.
First leaves of young seedlings small,
3-5 X 2-4 mm, ovate, with very short wingless petioles borne on numerous
slender, horizontal twigs with internodes often only 2-4 mm long, with
sharp, slender spines, 7-12 mm long, at the nodes; the upright twigs of
young plants have similar leaves and spines but the internodes are
sometimes 5-8 mm long; the upright, strongly angled, vigorous twigs of
mature trees, which have internodes 8-12 mm long with single sharp
spines, 5-10 mm long, have lozenge-shaped leaves, 22-25 X 14-15 mm,
obscurely toothed in the upper half, gradually narrowed to a blunt,
truncate base with which the petiole articulates; lateral veins faintly
marked above, more clearly below, 6-10 pairs, arising at an angle of
35°-45° with the midrib, lower ones longer, upper ones soon branching,
all with several anastomosing curved cross-veins; leaves tapering into a
truncate or emarginate tip, those on lateral twigs 8-20 X 2-10 mm, the
smaller ones abruptly truncate, often irregularly emarginate; spines
slender, short, 3-8 mm long; flowers arising singly in the axils of the
leaves (or occasionally in pairs); flower buds subglobose or obovate, 4 X
5 mm, borne on very short pedicels, 1-2 mm long; flowers usually
5-merous but sometimes 3-4-merous; sepals free, small, concave, minutely
ciliate; petals oblong, 7-8 mm long; stamens 20-25, free, pistils
short, stout, ovary with 5-7 locules; ovules numerous, 8-16 (or even 20)
in each locule; fruits cylindric-fusiform, 6.5-10 X 1.5-2.5 cm, often
slightly curved, narrowed at both tip and base, often showing a blunt
protuberance at one or both ends; peel rough with numerous oil glands,
greenish-yellow at maturity; pulp-vesicles nearly free or loosely
cohering, long-stalked, ovoid, ending in a very blunt or rounded tip,
about 1.7-3 X 1.2-1.5 mm, borne on a slender stalk 1-2 mm long; seeds
numerous, small, 6-7 mm long, ovoid, monoembryonic, usually flattened on
one side and often showing small, shallow depressions on the other
faces (probably caused by mutual pressure of the pulp-vesicles exerted
during development of the fruit); testa smooth (not wrinkled as in Eremocitrus glauca); cotyledons hypogeous in germination.
This, the type species of the genus Microcitrus, has several characters separating it from all of the species of Citrus. It is also very clearly separated from the other species of Microcitrus by its very long, slender fruits that are unique in the orange subfamily (see fig. 3-44,E).
They have numerous seeds (or rudiments) in each segment (more numerous
than in any other true citrus fruit). The pulp is composed
of loosely grouped, long-stalked, subglobose or pyriform pulp-vesicles,
tapering bluntly to the tip. These pulp-vesicles are very
different from those of M. australis but are much like those of M. inodora; they also resemble somewhat those of Citrus (Papeda) hystrix, as noted by Penzig (1887, pp. 214-17), who was the first to describe the anatomy of the fruits, seeds, and pulp-vesicles of M. australasica. The
very acrid pulp has a harsh aftertaste, probably due to droplets of
acrid oil in the pulp-vesicles, such as have been found in the
Australian round lime. Francis (1929, p. 174) stated that
the fruits, both of this species and of M. australis, "have a lemon-like flavor accompanied by a taste of a turpentine nature."
The finger-lime of the coastal regions of
northeastern Australia is a tall shrub or small tree and makes a
handsome ornamental. The seedlings are very
spiny. The first leaves are minute linear cataphylls; these
gradually merge into juvenile foliage which, in turn, merges into the
mature foliage, the leaves of which are smaller than those of any other
True Citrus Fruit Tree with the exception of Eremocitrus glauca
when the latter occurs in very dry situations. The branches
on young plants often stand out nearly at right angles to the stem,
giving the young plant the appearance of a very dwarfed fir
tree. This species is precocious; Oliver (1911, p. 15)
figured a small branch of a two-year-old seedling bearing two fruits.
Uphof (1932, pp. 138-39), in an examination of five trees of M. australasica,
found that most of the flowers were male and that only a very few were
perfect. He examined the flowers on eight twigs and found,
out of 161 flowers, that 151 were male and that only ten were perfect.
Microcitrus australasica is of
interest in hybridization work because of the great vigor and the
extraordinary production of slender leafy twigs that have been shown by
the Sydney hybrid.
1a. Microcitrus australasica var. sanguinea (F. M. Bail.) Swing. Jour. Wash. Acad. Sci. 5:574. 1915. Citrus australasica var. sanguinea F. M. Bail. Dept. Agr. Queensl. Bot. Bul. 18:8. 1892. Illus. Penzig, Studi Bot. Sugli Agrumi, Atl. pl. 21, fig. 13. 1887.
Type.—Queensland (Bailey ?). Herb. Bot. Gard. Brisbane.
Distribution.—Australia: southeastern Queensland.
Common name.—Red-pulp finger-lime.
This variety differs from the species in
that the pulp-vesicles at maturity vary from pink to red in color.
There are similar "pink" or red varieties
of oranges (the so-called "blood oranges") and grapefruit, some of
which are known to have arisen as budsports. However, the
red-pulped variety of the Australian finger-lime is found growing wild
and can be propagated from seed; it seems to have originated without the
aid of man.
HYBRIDS
Faustrimedins [Microcitrus australasica X (Fortunella sp. X Citrus sp.) 'Calamondin'].
This trigeneric hybrid is discussed under Fortunella.
2. Microcitrus australis (Planch.) Swing. Jour. Wash. Acad. Sci. 5:575. 1915. Limonia australis. A. Cunn. nomen subnudum. 1839; Citrus australis Planch. Hort. Donatensis 18. 1854-1858; C. planchoni F. Muell. 1872. Illus. Penzig, Studi Bot. Sugli Agrumi, Atl. pl. 21, fig. 8-13. 1887; Campbell, Agr. Gaz. N. S. Wales 10:1168. 1899; Guilfoyle, Austr. Pl. pl. facing p. 123. 1911; Bailey, Comprehen. Cat. Queensl. Pl. 84, fig. 62. 1913; fig. 3-44,A-B this work.
Type.—Moreton Bay, Queensland (Leichhardt). Herb. Mus. Hist. Nat., Paris.
Distribution.—Northeastern Australia.
Common name.—Australian round lime.
Leading terminal twigs straight, very
angular, with internodes 1-1.5 cm long, with single slender acute thorns
5-10 mm long; lateral twigs short, slightly angled, with internodes
5-10 mm long, and spines 2-6 mm long; leaves entire, glabrous, or
sparingly ciliate on the margin near the base; leaves articulated with
the petioles; larger leaves on leading twigs 3-4 X 2-3 cm, obovate to
obcordate (sometimes lozenge-shaped on less vigorous leading twigs);
leaves of lateral twigs diamond-shaped, 2-3 X 1.2-1.8 cm; veins visible
on both surfaces, but more conspicuous below, 12-15 pair arising at an
angle of 25°-30° with the midrib and frequently branching, with veinlets
arising at a very acute angle and running parallel to the veins; leaves
rounded, emarginate or bluntly pointed at tip, cuneate at the base;
petioles articulated with the leaf blades, finely pubescent and
flattened an the upper side, 2-3 mm long; flowers arising singly in the
axils of the leaves, small, 10-15 mm diam., 4- or 5-merous, with 16-20
stamens with free filaments; fruit globose or subglobose, 2.5-3.5 or 5
cm diam., with 6 segments (Schaler's green to grass green; Ridgway,
1912, pl. 6); pulp-vesicles proper (exclusive of stalk) 6-10 X 2.5-3.5
mm, lightly coherent in mature fruits, very pale greenish (water-green,
Ridgway, pl. 41) near the peel but much brighter green (light
grass-green to grass-green, Ridgway, pl. 3) in the center, irregularly
slender-pyramidal or fusiform, more or less angular from pressure,
tapering gradually into long, more or less contorted blunt tips, 1-1.5
mm wide, containing numerous large droplets of strong-flavored oil,
stalks often very short, sometimes 2-3 mm long, texture of pulp-vesicles
firm enough to cut into slices with a sharp knife (much firmer than in
any species of Citrus); seeds flattened, containing a single embryo; no clearly defined chalazal cap in spite of the acid nature of the pulp (in Citrus the species with acid pulp have strongly colored chalazal caps).
This species, called "Dooja" by the
aborigines and round lime or native orange by the Australians, is native
to northeastern Australia. It is readily distinguished from
all the other species of Microcitrus (and from Eremocitrus as
well) by its globose or slightly pear-shaped, rough-skinned fruits, 2.5
to 5 cm in diameter (about the size of a large walnut), and by its
short-stalked pulp-vesicles that taper gradually into blunt tips often
more or less deformed and twisted by mutual pressure (see fig. 3-44,B).
The early descriptions of this species and of M. australasica
are so meager as to leave doubt concerning which species was being
discussed. Fortunately the original descriptions of Citrus australis, published by Planchon in a rare work (Hortus donatensis,
1854-58, p. 18), was based on a specimen in the herbarium of the Muséum
d'Histoire Naturelle at Paris, collected by Leichhardt in the vicinity
of Moreton Bay in southeastern Queensland. A study of this
type specimen makes clear the proper application of the name M. australis.
Penzig (1887, pp. 210-17, pl. 21, figs.
8-13) described in detail the anatomy of this species. He
found that the pulp-vesicles were similar to those of the commonly
cultivated citrus fruits except that they contain, along their central
axis, large masses of yellowish oil. These pulp-vesicles are
very different in shape from those of the finger-lime, M. australasica, or those of the other species of Microcitrus.
The Australian round lime, or Dooja,
grows to be a tree 30 to 60 feet high and is the largest of any of the
native citrus fruit trees. The fruit is said to be used for
preserves in Queensland. This species, which has been
introduced into the United States, grows well in California, where it is
now fruiting. It is exceeded in vigor, however, by the
Sydney hybrid, the result of a natural cross of this species with the
finger-lime, Microcitrus australasica.
HYBRIDS
Sydney hybrid19 [Microcitrus australis X M. australasica]. Illus. fig. 3-44,C and D.
Twigs very slender and very numerous,
usually only lightly angled, very minutely and rather sparsely
puberulous; bud scales brownish, inconspicuously ciliate; nodes 5-13 mm
long, with a single slender, sharp, axillary spine, 4-12 mm long; leaves
on vigorous leading twigs 20-30 X 8-13 mm, glabrous, narrowly
elliptical or lozenge-shaped, with undulate or irregular, shallowly
crenate-dentate margins, narrowed at the apex, sometimes with an
emarginate tip, cuneate at the base, with numerous lateral veins arising
at a small angle (25°-35°) with the midrib, with some cross and some
subparallel veinlets, narrowed into very short petioles, 2-3 mm long
which are sparingly and finely pubescent above; leaves on lateral twigs
10-20 X 3-8 mm, linear-elliptic or narrowly lozenge-shaped, the smaller
leaves entire, the larger with undulate or irregular, shallowly dentate
margins, petioles 1.2-2 mm long; fruits elongate-obovoid or ellipsoid,
35-50 X 20-28 mm, with the tip abruptly rounded, numerous slightly
protuberant oil glands, circular in outline and about 0.5 mm diam., peel
2 mm thick, yellowish-green when ripe (near lime green, Ridgway, pl.
31); inner portion 0.4-0.5 mm thick, smooth, of firmer texture than the
outer, segments 5-8 central core solid, very narrow, ovule traces
numerous; pulp-vesicles ovoid, tapering to an acute point above, broadly
rounded at base, 4.5-7 X 2-4 mm, borne on slender stalks, 2-7 mm long,
attached to inner wall of the ovary but not to segment walls, not
adhering to one another, containing an acid juice; seeds
none. The ripe fruits have a spicy, not disagreeable
odor. The flower buds are spinel red, and the new growth is
very dark dull dusky purple (Ridgway, 1912).
This remarkable hybrid was grown from seeds of the Australian round lime, Microcitrus australis, or of the finger-lime, M. australasica,
sent to the U.S. Department of Agriculture's Agricultural Research
Service by the late J. E. Maiden, director of the Botanical Garden at
Sydney, Australia. More than 200 meters of twigs, both large
and small, were borne on a single branch, 3 cm in diameter, of a Sydney
hybrid growing near Riverside, California, which survived for several
decades on land no longer irrigated where citrus trees made little or no
growth.
The leaves are intermediate in shape
between the two parent species, but, owing to the enormous number of
twigs and consequent great profusion of leaves, they are not
intermediate in size between those of the parent species, but nearer
that of the small-leaved parent, the finger-lime. The leaf
margins are more crenate than those of either parent. The
small twigs of both parents are minutely ciliate, but the larger angled
twigs, especially of the finger-lime, are almost glabrous.
In the hybrid, however, the twigs are more pubescent than those of
either parent and are more slender and more upright.
This hybrid has been found to support the
orange and other commonly grown citrus fruits very well in greenhouse
culture, and it can be propagated readily from soft-wood cuttings of
summer growth. As it excels all known citrus fruit trees in
the length of twigs it produces, it should be tested as a stock for
citrus fruits grown on foothill soils low in organic
nitrogen. On account of its extremely abundant branchlets
covered with miniature leaves, the Sydney hybrid deserves trial as an
ornamental, especially in the orange-growing section of the southeastern
states.
3. Microcitrus garrowayi (F. M. Bail.) Swing. Jour. Wash. Acad. Sci. 5:574. 1915. Citrus garrowayi F. M. Bail. Queensl. Agr. Jour. 15:491. 1904. Illus. Bailey, Comprehen. Cat. Queensl. Pl. 84, fig. 65 (leaves and fruit). 1913.
Type.—Queensland, Mount White,
Cape York Peninsula, near Coen (Lat. 13° 55' S., Long. 145° E.),
altitude 1,300 feet (R. C. Garroway). Herb. Bot. Gard.
Brisbane.
Distribution.—Known only from the type locality.
Common name.—Garroway's Australian wild lime.
Bark with minute, irregularly interrupted
longitudinal ridges; young twigs very slender, 0.8-1.5 mm diam.,
cylindric or rarely slightly angled when very young, with very small
more or less upward curving, hyaline hairs; internodes 4-15 mm long
(usually about 6-10 mm), with very slender spines, 2-5 mm long, or
spineless; older twigs below last growth show gray, corky, longitudinal,
more or less confluent streaks, 0.5-1 mm wide, that show fissures
(these corky streaks become more and more abundant and finally run
together, so that two-year-old twigs show little or no green bark);
leaves of cotype specimen (from Mount White, Queensland) narrow, thick
and leathery, lozenge-shaped to broadly lanceolate, 30-45 X 15-20 mm
(small leaves 20-25 X 10-12 mm), bluntly pointed, rounded or even
slightly emarginate at apex, cuneate at base, with 5-7 pairs of veins,
visible on both surfaces of the leaves, arising at the midrib and
occasionally branching, margins nearly entire, slightly undulate; leaves
on leading twigs of greenhouse specimen 20-25 X 12-18 mm,
lozenge-shaped or broadly ovate, bluntly rounded or slightly emarginate
at apex, cuneate at base, margins slightly dentate or crenulate
especially toward the apex, with a few hyaline hairs on the margin at
the base of the leaf and still fewer on the lower portion of the midrib;
petioles 2-4 X 0.8-1 mm, wingless, flattened above, articulated with
the blade, finely pubescent on the upper flattened side, especially at
the edges; fruit of cotype specimen ellipsoid or cylindric-ellipsoid, 4 X
2 cm, with numerous sunken oil glands.
Bailey described this species as follows, under the name of Citrus garrowayi:
"Fruit upon the slender branchlets oblong, 2 1/2 in. long, 14 lines
diameter. Oil glands large, giving a tuberculose appearance
to the fruits; ultimately these glands sink, and the fruit appears then
to be lacunose; rind very thin; cells 4 or 5; pulp of a sharp agreeable
acid; seeds 3-angular, white, free, with more or less very short hairs,
about 3 lines long and 2 lines thick in the centre. The
rough rind of the fruit somewhat resembles that of C. australis, but the form of fruit is nearer to that of C. australasica; the fruit of this latter, however, is nearly smooth and the glands small."
Microcitrus garrowayi seems to be a good species, distinct from M. australasica and M. australis,
occurring farther to the south in eastern Australia. Bailey
called this the Mount White lime. It has been introduced
into the United States.
4. Microcitrus inodora (F. M. Bail.) Swing. Jour. Wash. Acad. Sci. 5:577. 1915. Citrus inodorus F. M. Bail. in Meston, Rept. Govt . Sci. Exped. Bellenden-Ker Range 34. 1889; C. inodora F. M. Bail. Syn. Queensl. Fl. 3d Suppl. 12. 1890. Illus. Bailey, Queensl. Fl. 1:pl. 10. 1899; idem, Comprehen. Cat. Queensl. Pl. fig. 64. 1913; C. T. White, Jour. Hered. 13:120, figs. A-E. 1922.
Type.—Queensland, Harvey's Creek,
Russell River (F. M. Bailey). Herb. Bot. Gard. Brisbane;
part of type material in Herb. Natl. Arbor., Washington, D.C.
Distribution.—Australia: northeastern Queensland.
Common name.—Large-leaf Australian wild lime.
Leaves broadly oval or lanceolate, or
with cuneate bases and more or less acute or even caudate at the apex,
8-18 X 4-10 cm, with very numerous, parallel, lateral veins arising at
an angle of 60°-80° with the midrib; petioles very short, 4-8 mm long,
wingless, not articulated with the blade; flowers small (as in other
species of Microcitrus) but reported by Bailey to be odorless; stamens free but much more numerous (over 30!) than in the other species of Microcitrus;
fruit oblong or elliptical (somewhat lemon-shaped), 5-6.5 X 3-3.5 cm,
with a conical base, segments 8, on drying sometimes showing ribs
corresponding to the walls separating the segments; pulp-vesicles
stalked like those of other species of Microcitrus, rather loose; seeds small, somewhat pear-shaped, 6-8 X 4-5 mm.
This species is a shrub or small tree 2
to 4 meters high with the trunk 4 to 5 cm in diameter. The
twigs are angular like those of Citrus sinensis (the sweet
orange) and have one or two slender, very sharp spines, 6 to 12 mm
long. It has been found growing wild only along Harvey's
Creek, Russell River, where, according to White (l.c., p. 119), it is
common in the lowland rain forests at the foot of the Bellenden-Ker
Range in northern Queensland near Cairns (Lat. 17° S.). This
is a very rainy region, the average annual precipitation being 170
inches. In February, 1922 (?), the rainfall was 62 inches!
5. Microcitrus maideniana (Domin) Swing. Jour. Wash. Acad. Sci. 28:533. 1938. Citrus maideniana Domin, Bibl. Bot. 89:297. 1927. [Beiträge z. Fl. Austr. 851].
Type.—Northeastern Queensland,
rain forest along Harvey's Creek (Domin, December 1909, to January
1910). Herb. Univ. Praha, Czechoslovakia.
Distribution.—Known only from the type locality.
Common name.—Maiden's Australian wild lime.
The original diagnosis reads, in
approximate translation: "A low erect shrub, 1.5-2.5 m high; young twigs
angular-compressed; spines numerous on the twigs, two in the axil of
each leaf, of which one spine is occasionally shorter; leaves lanceolate
or ovate-lanceolate, pale green, midrib rather prominent; fruit borne
on a short thick pedicel, obovoid-ellipsoid, when ripe about 4.5 cm long
and 2.5 cm wide or sometimes less, yellow, smooth, with 8 obtuse ribs,
not clearly visible in ripe fruits, apex deeply sunken; young fruits
deep green with closely set dusky green spots.
"A new species named in honor of the late
Professor J. H. Maiden of Sydney; it appears from the description to be
related to Citrus inodora F. M. Bail. from the same locality, but, besides the smaller fruits, the deeply sunken apex shows it to be distinct."
It is highly probable that this species is very closely related to Microcitrus inodora,
native to the same locality, with which it agrees in having paired
spines and more or less clearly eight-ribbed fruits (doubtless having
eight segments). The deeply depressed apex of the fruit is
the only clearly distinctive character known as yet.
6. Microcitrus warburgiana (F. M. Bail.) Tan. Bul. Soc. Bot. France 75:714. 1928. Citrus warburgiana F. M. Bail. Contr. Fl. Brit. N. Guin. 1. 1903. Illus. Bailey, loc. cit. first unnumbered plate, lower half (leafy twigs and fruit); fig. 3-45 this work.
Type.—Southeastern British New Guinea, Milne Bay (W. E. Armit). Paratype: U.S. Natl. Herb., Washington, D.C. (from F. M. Bailey!).
Distribution.—Known only from the type locality.
Common name.—New Guinea wild lime.
The original description reads as
follows: "Branchlets angular, soon becoming terete, apparently quite
glabrous; axillary spines erecto-patent, about 2 lines long on the
specimen seen. Leaves rhomboid-lanceolate, 1 1/2 to 2 1/2
in. long, 5 to 11 lines broad, deeply emarginate and the margins
crenulate for 2/3 the way down; primary nerves rather numerous and very
oblique, the intermediate ones and reticulate veins rather
prominent. Petioles light colored, 2 to 3 in. long, very
narrowly winged. (No flowers collected.) Fruit
axillary on a stout peduncle, 1 1/2 lines long, globose, about 3/4 in.
diam., oil glands concave, crowded, rind thin, cells 6. This
species seems to be nearly allied to C. Medica, var. aruensis, Warbg., Engl., in Bot. Jahrb., 1891, page 340."
A twig of the type collection sent to
Swingle by Bailey shows characters as follows: Twigs 30 cm long, 2 mm
diam. at base, with very slender terminal twigs only 0.5-1 mm diam.,
internodes 1-2.5 cm long (rarely 5 mm on the slenderest lateral twigs),
slightly angled at first but soon cylindrical, minutely puberulous at
first but apparently soon glabrescent; leaves elongate-elliptical, leaf
blades 4-6 X 1-1.8 cm, coarsely but shallowly crenulate-serrate, bluntly
rounded at apex and often slightly emarginate, bases cuneate,
subentire, lateral veins 10-12, connected by numerous smaller
subparallel reticulating veinlets; petioles subulate, very short, 2-3 mm
long, 0.5 mm thick, 0.8-1 mm wide, articulated with the leaf blade,
with slightly depressed channel on the upper side bordered along the
upper half by a slightly crenulate membrane (in drying, sometimes curved
upward and making a nearly closed channel), sparingly and minutely
puberulous on the upper side and on the margins.
The small globular fruits, the
elongate-elliptical, crenulate leaves, and the narrowly
subcrenulate-margined, very short petioles separate this New Guinea
species very clearly from the other species of Microcitrus. This is the only species of the genus outside of Australia, and it occurs nearly a thousand miles away from M. garrowayi, the Australian species of Microcitrus growing nearest to New Guinea.
The fruits are small, globose, with six segments (fig. 3-45).
Bailey's description, however, says nothing concerning the character of
the pulp-vesicles, if any! The petioles differ from those
of the other species of Microcitrus in having a very narrowly
crenulate margin or wing. The veins are numerous, making
only a small angle (35° to 50°) with the midrib, and soon branch,
forming a reticulation of veinlets not unlike those of M. garrowayi,
although the latter species has smaller leaves with fewer
veins. The ultimate twigs, especially the short lateral
branchlets, are remarkably slender, the smallest lateral twigs being 1
to 1.5 mm or even only 0.5 to 0.8 mm in diameter.
XXVI. Citrus L.
XXVI. Citrus L. Sp. Pl. 1:401. 1753. Citrophorum Neck. Elem. 1:401. 1790; Sarcodactylis Gaert. f. Fruct. Sem. 3:39, pl. 185. 1805; Papeda Hassk. Flora, 25, Beibl. 2:42. 1842.
Type species.—Citrus medica L.
Distribution.—Southeastern Asia,
East Indian Archipelago, Philippines, New Guinea, New Caledonia,
Bismarck Archipelago, Solomon Islands, Fuji (?), Samoa (?).
Small trees; young twigs angled, soon
cylindrical, with single spines in the axils of the leaves but older
branches often spineless; leaves 1-foliolate, usually thin, not
coriaceous, lateral veins few and without conspicuous reticular veinlets
between; petioles usually more or less winged and articulated with the
leaf blade (except in C. medica, where they are wingless or
merely margined and not articulated with the leaf blade); flowers single
in the axils of the leaves or in short, axillary, corymbose racemes,
perfect or staminate by more or less complete abortion of the pistil;
calyx cup-shaped, with 4-5 lobes; petals 4-8 (usually 5), thick, linear,
strongly gland-dotted, imbricate in the bud; stamens usually about 4
times as many as the petals but in some species usually 6-10 times as
many; disk annular, short; ovary subglobose and sharply distinct from
the much narrower style, or else truncated, fusiform, or subcylindrical
and merging gradually into a style nearly as thick as the upper portion
of the ovary, locules 8-18 (usually 10-14), with 4-8 or more ovules in
each locule in 2 collateral rows; style cylindrical, expanding abruptly
into the subglobose or oblate-spheroid stigma; fruit a hesperidium with
the segments containing seeds near the inner angle and the rest of the
space filled with stalked fusiform pulp-vesicles, filled with a very
watery, large-celled tissue; around the segments is a white endocarp,
outside of which is the peel dotted with very numerous oil glands and
turning yellow or orange at full maturity; seeds obovoid or flattened
obovoid, more or less angular, containing 1 or many embryos, either
white or green.
In young developing fruits of Citrus short-stalked,
club-shaped slime-secreting organs develop rapidly along with the
pulp-vesicles. These, however, soon mature and liberate,
from collapsing superficial cells of the head, slimy matter which
probably enables the developing pulp-vesicles to slide freely over one
another (see Tschirch and Oesterle, 1898, p. 303, pl. 70, figs. 36, 36a, 36b, 36c, and 38). Similar organs probably occur in the other genera of the True Citrus Fruit Trees, but in the subgenus Protocitrus of the genus Fortunella these slime-secreting organs are sessile and are not intermixed with the developing pulp-vesicles.
The genus Citrus, thanks to the
progress made in the taxonomic study of the orange subfamily in the last
half century, can now be seen in proper perspective. It is
the culmination of a very long period of progressive evolution that
certainly began before Australia was cut off from land connection with
New Guinea and Asia, probably more than 20 million years
ago. The genus Microcitrus, closely related to Citrus, occurs both in southern New Guinea (one species) and in northeastern Australia. A related genus, Eremocitrus, originated in Australia and became a xerophyte adapted to grow in semiarid regions. Citrus
occurs in New Caledonia, but only one species is known there or in
neighboring islands to the east and southeast. The genus may
have originated in the New Guinea-Melanesia region, but its evolution
into many different species took place chiefly on the mainland of
southeastern Asia. In fact, it is only there that the most
highly developed species of Citrus can be considered as indigenous. Only the aberrant species belonging to the subgenus Papeda
have developed in the East Indian Archipelago, and in the Philippines,
New Guinea, and Melanesia. A few of these species reached
the Asiatic mainland, and from these sour and bitter-flavored, almost
inedible species have doubtless developed the fragrant,
delicious-flavored species of the subgenus Citrus, in many ways the finest fruits known to man.
The superiority of these finer species of Citrus has
led to their extinction as wild plants because their fruits made them
so attractive that the trees were transplanted to village
gardens. This led to cross-pollination by bees and other
insects, with the resultant obscuring of species limits to the extent
that in many parts of southeastern Asia and in the East Indian
Archipelago it is difficult to find any clear-cut species of Citrus. There
appears instead, an endless array of complex hybrids, often combining
not two, but three or even four, different species in varying
proportions. This situation has led to much confusion in
attempting to define species of Citrus. As will be shown later, it is necessary to abstain from naming the principal cultivated varieties of Citrus
as independent species. Unfortunately, names have sometimes
been given even to almost sterile varieties, doubtless of hybrid
origin, that depend wholly on man's care for their perpetuation.
THE SPECIES CONCEPT IN THE GENUS CITRUS
About a century and a half ago, several
treatises were published on the citrus fruit trees. The
first of these was the Traité du Citrus, by Georges Gallesio
(1811), followed by the work of J. A. Risso (1813) and J. L. A.
Loiseleur-Deslongchamps and Etienne Michel (1818), and finally by the Histoire naturelle des orangers of
Risso and A. Poiteau (1818-1822). In these voluminous
works, every cultivated variety was given a name consisting of a Latin
phrase of from three to ten, or even more, words. As these
polynomials did not fit into the Linnaean system of plant nomenclature
then in universal use by botanists, they were never incorporated into
the taxonomic literature, especially since botanists considered that
hybrids and monstrosities originating in orange houses or gardens were
not deserving of technical botanical Latin names.
The view of professional botanists on
this plethora of names is perhaps best indicated by quoting a paragraph
relating to the genus Citrus written by Daniel
Oliver. In his monograph on all the other genera of the
orange subfamily occurring in India, Oliver (1861, p. 1) gave his
reasons for not attempting to treat the species of Citrus. He wrote: "Feeling it utterly hopeless usefully to define them [the species of Citrus],
I have thought it best to leave the Oranges, Lemons, Limes and their
allies as I found them. It has been difficult to form, for
purposes of comparison, any satisfactory approximate estimate of the
number of species in this very variable and widely cultivated
genus. From the data afforded by Risso, Loureiro, Wight and
Arnott, Miquel, and others, and from what I have myself seen of dried or
living specimens, I have assumed five as about the probable number."
Fourteen years later, in 1875, J. D. Hooker in his Flora of British India included Citrus among the thirteen genera that he recognized as comprising the orange subfamily, but recognized only four species in Citrus, in India proper, Ceylon, and Burma!
As late as 1896, Adolph Engler, who for
many years had specialized on the Rutaceae, recognized only six species
of Citrus for the entire world, and in these he included three
species now placed in other genera. Finally in 1931, as his
last and greatest taxonomic contribution, Engler revised his account of
the Rutaceae for the second edition of Die naturlichen Pflanzenfamilien. In this he included eleven species in the genus Citrus and some six or seven species (which he had placed in Citrus in 1896 but now considered to be distinct) in the two genera Poncirus and Microcitrus.
In the meantime, early in the present
century, evidence of the most convincing sort, based on many hundreds of
accurately safeguarded cross-pollination experiments made by the citrus
experts of the former Bureau of Plant Industry of the U. S. Department
of Agriculture, began to be published. This evidence showed
that all the species of Citrus tested, and also species of two
other related genera, could be hybridized without difficulty and that
these hybrids often manifested astonishing variability in the first
generation. What was even more surprising, many of these
hybrids, especially those between rather remotely related species, bore
apparently normal seeds that reproduced the parent hybrid
exactly. In reality it was found that such hybrids often
produced no viable egg cells, but, if pollinated, tiny buds from the
nucellar tissue of the mother plant would grow into the embryo sac and
there develop into apomictic embryos that, of course, reproduced the
mother plant exactly (Traub and Robinson, 1937).
It is therefore highly probable that in
China, Japan, India, and other Oriental countries accidental
hybridization has occurred in dooryard or village plantings of assorted
citrus fruit trees through the action of bees and other insects which
seek the abundant nectar of Citrus flowers. It is
also reasonable to suppose that if hybrids did arise and if chance
seedlings came into fruiting they would be propagated by the villagers
if the trees bore fruit of superior quality.
Many year of intimate contact with the
citrus hybrid populations gave Swingle and his colleagues a clear
understanding of the characters and nature of some of the more valuable
of these hybrids between different species of the commonly cultivated
citrus fruit trees. Armed with this experience, Swingle made
three trips between 1915 and 1926 to the citrus-growing regions of
Japan, China, and the Philippine Islands, where he paid special
attention to hybrids and mutations of pummelos, oranges, and other
citrus fruits. He recognized in Oriental villages many of
the types of hybrids that had been made in the United States by
carefully safeguarded cross-pollinations! In the Orient,
these had originated as accidental hybrids, doubtless due to
cross-pollination by insects. For example, citranges,
hybrids of the trifoliate orange and the sweet orange, were found
growing in dooryards in the Yangtze Valley region of China, and
tangelo-like fruits, undoubtedly hybrids of pummelos and loose-skinned
citrus fruits, were not uncommon in Japan! After the mass of
evidence regarding the origin and nature of citrus hybrids was brought
to light and published in detail in well-illustrated papers, evidence
that proved the possibility of producing large numbers of striking new
forms of citrus fruit trees by cross-pollination of the commonly
cultivated species of Citrus, it is indeed surprising that A. W.
Lushington in India, in 1910, and T. Tanaka in Japan, from 1924 to date,
should have given species rank to scores of citrus forms that
undoubtedly are hybrids.
Tanaka (1935b, p. 576) realized
that many of his "secondary or miscellaneous" species are chance
hybrids. In discussing the fifteen so-called "primary
elements or species" of Citrus, Poncirus, and Fortunella,20
and the "secondary or miscellaneous species derived from them," he
stated that the lack of secondary species among the pummelos (Citrus grandis)
of southern China, "is to be explained by the lack of cooperation of
compatible elements (species) acting as the mating pair to originate new
species."21 Actually, one of the conditions that hinders the hybridization of C. grandis
with other species is that the anthers lie against the stigmatic
surface and release their pollen before the bud opens. Later
Tanaka stated: "Compatible combinations of primary species22 encourage the creation of such secondary elements…of great significance to the evolution of the Citrus flora of the world."
In 1932 Tanaka (1932d, p. 263) made the following statement concerning the Calamondin orange: "The admittance [acceptance] of Citrus microcarpa [= C. mitis, a distinct bigeneric hybrid between Citrus and Fortunella]
is another of the endless examples, which present no contradiction to
the writer's system of nomenclature…" Tanaka also stated
explicitly (1927a, p. 54) that new forms of Citrus to
which he had given taxonomic rank as genuine new species might have
arisen from "chance seedlings." He considered that the
Japanese Natsudaidai, which he held to be a good species (C. natsudaidai
Hayata), was "unquestionably a chance seedling originated at Hagi in
Yamaguchi Prefecture." He also considered the satsuma orange
to be "botanically a good species, Citrus unshiu Marc.," that
had originated some centuries earlier in western Japan as a chance
seedling of one of the famous oranges of Hwangyen, Chekiang Province,
China. In discussing the cultivated Ichang lemon (probably a hybrid of the Ichang papeda, C. ichangensis Swing., with some other species of Citrus grown in central China), which he named C. wilsonii (1932b, p. 37). Tanaka stated: "The present species unquestionably has Citrus junos in
one parent and seems to be a cultigen originated through the chance
seedling." There is no proof, however, that any one of the
chance seedlings discovered and propagated by man as cultigens could
have persisted and become established as a wild species.
The taxonomic delimitation of species, subspecies, and forms in Citrus
and closely related genera is complicated by three peculiarities in the
reproduction of citrus fruit trees: (1) polyembryony through formation
of nucellar-bud embryos, (2) rejuvenation by neophyosis of such
nucellar-bud embryos of more or less senescent varieties long propagated
asexually, and (3) the spontaneous production of autotetraploid forms.
Hybrids of Citrus, both
intergeneric and intrageneric, are frequently egg-sterile; yet, when
pollinated, they often set seeds. These seeds are devoid of
sexually derived zygotic embryos ("gametic" embryos of some authors),
but contain one or more embryos within the embryo sac apomictically
produced by ingrowing buds arising from the adjoining undifferentiated
nucellar tissue of the female parent. This phenomenon was
first described by Strasburger (1878) and later was discussed by Frost
(1626) and Traub (1936). Such nucellar-bud seedlings
reproduce the mother plant exactly, so that many violent F1 Citrus hybrids, such as citranges (C. sinensis X Poncirus trifoliata) and tangelos (C. paradisi X C. reticulata),
reproduce perfectly from seeds and sometimes are grown on a large
scale. Taxonomists have found such egg-sterile hybrids to be
confusing, since they do not show the usual wide variation in the
second generation characteristic of normal F2 seedlings but behave like very constant true species.
In many species of Citrus, such
nucellar embryos may occur together with the zygotic embryo.
In such cases, the zygotic embryo may produce a plant that varies
somewhat in its characters from the mother plant, whereas the nucellar
embryos reproduce the mother variety almost exactly.
Nucellar-bud seedlings as well as sexual seedlings apparently restore
the variety to its primitive or juvenile condition, because such plants
not only develop spines abundantly but show greater energy of growth and
greater hardiness and sometimes produce somewhat larger or otherwise
superior fruit. Two nucellar strains of a well-known
mandarin orange (Dancy tangerine) were named the Weshart and Trimble
tangerines by Webber and Swingle (1905, pp. 238-40 and pl.
20-22). The Silverhill satsuma is another striking example
of a nucellar seedling of the Owari satsuma (see Swingle, 1931).
Similar rejuvenation of nucellar
seedlings was observed in experimental work with the Washington navel
orange where there could be no confusion between the zygotic and the
nucellar embryos arising from the same seed, since the zygotic embryos
were citranges obtained through pollinations with Poncirus trifoliata. This rejuvenation of the old cultivated varieties of Citrus has
been called neophyosis (see Swingle, 1932, 1933). Nucellar
strains of old varieties rejuvenated through neophyosis might easily be
mistaken for taxonomically distinct varieties or even subspecies,
because of their vigorous growth, their large leaves and fruit, and
their luxuriant development of spines which are often lacking on
varieties long propagated vegetatively.
Finally, thick-leaved seedlings of several species of Citrus were found by Frost (1925, 1926) to be autotetraploid
forms of the parent species; the fruits have a thicker rind with larger
oil glands, are usually more depressed-globose, and have less juice,
and more and larger seeds than the diploid parental species from which
they originated.
As a matter of fact, from the standpoint
of phylogenetic taxonomy, which records the evolutionary descent of
natural wild species, only Tanaka's "primary elements or species"
deserve consideration as true species; chance seedlings, mutations, and
hybrids, propagated usually by grafting, should be given a status
similar to cultigens of apple or rose varieties that no taxonomist of
standing has proposed to name as good species, although they often
exhibit important differences in flowers or fruits or other organs as
well.
Once this nomenclatorial confusion is
cleared up, Tanaka's studies of the myriad cultivated races of Citrus and Fortunella
in the Far East will be appreciated at its full value and he will
receive recognition as having greatly advanced the study and
classification of citrus fruits. This task can then be
carried on without upsetting the scientific taxonomy of Citrus and Fortunella, which is based on the native wild species originally propagated spontaneously from seed without human help.
A. E. Kozhin, the well-known Russian
citrologist, published a notable paper on the citrus fruit (1931) in
which he gave particular attention to the very extensive literature on
the subject and to the taxonomic history of Citrus and the genera
most closely related to it. He strongly objected to the
practice of considering "garden species" as species in the taxonomic
sense. He contrasted such false species, some of them
seedless and unable to live at all without man's help and most of them
propagated by clones, with true species. He said in part:
"…a Linnean species is a whole system of elementary forms which,
continually crossing with one another, keep within the limits of
definite specific characters. In drawing up such a system of
forms, the geographic moment, i.e., the conditions of habitat, play an
important role…From this point of view the attempt to introduce into the
system as equivalent members (as has been done by Tanaka), the
wide-compassed Linnean species and such narrow forms as garden species,
frequently seedless ones, is a failure."
More recently Stebbins (1950) discussed
the species concept in agamic complexes, and stated that "…the species
concept…maintained by the majority of those who desire a truly
biological concept of species, centers about the possibility for
exchange of genes between members of the same species and separation of
different species by barriers to the exchange of genes.…Such a concept
cannot be applied to agamic complexes. Free exchange of
genes between apomicts is prevented by the very nature of their type of
reproduction, while the origin of many apomictic clones is from
genotypes which have combined the genes of previously isolated sexual
species, and which without apomixis would not be able to persist because
of their sexual sterility. It is not strange, therefore,
that systematists have not been able to agree on the boundaries of
species in…[apomictic genera]." Stebbins continued: "In
attempting to set up species like those in sexual groups, they are
looking for entities which in the biological sense are not
there. Nor are those 'splitters' who make a separate species
out of every apomictic clone…likely to provide any better concepts of
the variation patterns in the genera concerned.…One criticism is that
the number of apomicts in any well-developed complex is so large that
recognizing them as separate species makes the comprehension of the
group as a whole difficult or impossible; one cannot see the forest for
the trees! But more important is the fact that in many
complexes the great majority of the apomicts, and in nearly all
complexes at least some of them, are only partly or facultatively
apomictic. From time to time they reproduce sexually, and on
such occasions a whole series of new clones, or 'species', may arise in
the offspring of a single individual." Once "splitting" is
begun on the basis of fruit characters or small detail, it would be
possible to justify thousands of species in the genus Citrus.
Furthermore, this number would be constantly augmented by additional
"species" as the citrus breeder produces new apomictic hybrids each
year. As Lawrence (1951) has pointed out, the presence of
apomixis makes possible the survival of hybrids that would otherwise be
eliminated under natural conditions by their sterility.
Lawrence stated, "The perpetuation of these apomictic hybrids has
resulted in some descriptive taxonomists treating each biotype as a
morphologically distinct and seed producing species."
Two major systems of citrus taxonomy and
nomenclature have developed. Swingle's system is presented
here. The other is the system proposed by Tyôzaburô Tanaka
(1927c, 1935a, 1954, and 1961), and supported by Yuichirô
Tanaka (1948). Each taxonomic treatment is based upon years
of research and study by very competent men of widely divergent
viewpoints.
Swingle began the first known attempts at
artificial hybridization of citrus in 1893. His experience
as a citrus breeder and his observations of large seedling populations
produced by controlled cross-pollination lead to the development of his
system of classification. He assembled an extensive
collection of Citrus material for study upon which he based this system.
Reece, the junior author, who was given the task of revising this chapter for this edition of The Citrus Industry, makes no pretense of competence in the field of taxonomy. On the other hand, he has devoted many years to Citrus breeding. He considers that Swingle's system comes closest to the truth of Citrus taxonomy, and he cannot accept the Tanaka system with its excessive splitting.
In following up his interest in Citrus taxonomy,
Tanaka has traveled widely and observed a wide range of
citrus. He is familiar with both the original literature and
herbarium material. Swingle and Tanaka became associated
and collaborated together at various times between 1915 and 1930 in this
country and Japan. Nevertheless, their divergent viewpoints
are apparent in their systems and conclusions. Their
disagreement is confined principally to the species problem in the genus
Citrus.
Although Tanaka in 1935 recognized only fifteen primary species in Citrus, Poncirus and Fortunella, he also stated, in an English summary of a Japanese paper (Tanaka, 1935a): "The author [Tanaka] enumerated 74 species as such well-established species of Citrus, Fortunella and Poncirus in
the present paper, but the mobilization of all species from various
Citrus districts is now on the way of progress." In a later
paper (1937), he listed no fewer than four additional "species" of
Lushington (published in 1910) and described six new species himself, as
well as four new varieties, all from India. In several
papers since 1935, he mentioned en passant many other new species
or varieties without describing them. This brought the
total to about 100, but the end was by no means in sight.
Tanaka (1954) established the foundation for his classification system with the publication of Species Problem in Citrus. In that work, he classified the forms of Citrus
into two subgenera, eight sections, thirteen subsections, eight groups,
two subgroups, two microgroups, and 145 species. Seven
years later (Tanaka, 1961), his system was expanded to include two new
subsections, Eulimonellus and Megacarpa, one new group, Paranobilis,
and twelve new species. Further refinements have continued,
however, and a classification chart sent by Tanaka to some of his
colleagues in 1966 contains five new subsections and includes 159
species. In contrast to the Tanaka system, the Swingle
classification recognizes two subgenera: the subgenus Papeda containing six species, and the subgenus Citrus (formerly Eucitrus) with ten species. A comparison of the major classification systems of the genus Citrus is presented in table 3-3.
Systematics are given for the Tanaka classification of 1961, which
contained 157 species, and the Swingle classification of 1943 followed
in this chapter. In addition, the table includes columns for
species recognized by the pre-Englerian, Englerian, and early Swingle
and Tanaka systems.
Tanaka recognizes thirty-five species of
mandarins. In some cases the only distinguishing character
in his key is leaf size or fruit size. Anyone familiar with Citrus
production knows that size is easily influenced by rootstock, soil,
amount of moisture, fertilization, and weather conditions prevailing
during development of a particular flush of growth.
Tanaka's arguments for granting species
rank to some of the mandarins are interesting and often quite
unique. In regard to making the satsuma a separate species
from Citrus reticulata, he says: "Pulp qualities are…the real
object of human interest to consume the fruit. The public
knows more about such specific distinction than a few technicians
because they consume more. To the Japanese, who eat 500,000
tons of satsuma fruit a year, they would never believe it to be a mere
variety or clone of either the Ponkan (C. reticulata) or Kunenbo (C. nobilis),
as is true to Americans not admitting the grapefruit as a variety of
the pummelo (Shaddock). It is a human belief and science
should endorse it." (See Tanaka, 1954, pp. 20-21.)
In support of his argument that the Ponkan, the Dancy tangerine, and the C. crenatifolia of Lushington are separate species and not varieties of C. reticulata,
he comments that "if these three should belong to a single species,
350,000,000 Indian people would not believe in science."
However, the objective of science is to seek the truth rather than the
support of human beliefs. Nevertheless, few biologists doubt
that new species can result from hybridization, but the new species
should be able to perpetuate itself by sexual methods. It
should not be dependent upon man for some type of vegetative
propagation. For this reason a number of Tanaka's "species"
are not considered valid by the authors. Furr and Reece
(1946) found "Citrus temple and C. clementina of Tanaka"
unable to reproduce their type even by nucellar embryony because nearly
all embryos are zygotic. Reece and Childs (1962) in a study
of a seedling population of Persian lime (C. latifolia Tanaka) have shown that this variety is apparently a hybrid between a seedy lime (C. aurantifolia Swing.)
and citron as the other parent. If, indeed, a seedy lime
and a citron were the parents of the Persian lime, the appearance of the
many lemon types of seedlings in the population supports Swingle's
hypothesis that the lemon may be of "hybrid origin, perhaps having the
citron and the lime for parent species."
Santiago (1962), in a guide to Malayan
nomenclature of citrus species, followed Swingle's system of
classification with a few exceptions. Bhattacharya and Dutta
(1956), in their comprehensive monograph on the citrus fruits of Assam,
followed Swingle's system in a general way, but accept C. nobilis Lour., C. karna Raf., C. limetta (Risso) Lush., C. jambhiri Lush., and C. megaloxycarpa Lush.,
five species of the Tanaka system that were not accepted by
Swingle. They find the nomenclature of one of these Tanaka
species invalid (C. pennivesiculata Tanaka = C. megaloxycarpa Lush.), and they name one new species found in Assam (C. assamensis Dutta and Bhattacharya, sp. nov.). This is known as ada-jamir
or the ginger citrus of India because people consider its aroma similar
to that of ginger. It is taxonomically close to C. hystrix DC., but differs from it to an extent considered sufficient by these authors to deserve a separate rank.
Several other systems of citrus
classification have been put forward by various authors.
Perhaps the one that has received the least attention by contemporary
students of Citrus taxonomy is the system proposed by Marcovitch (1926), which bases classification on leaf and flower characteristics only.
Wolfe (1959) has criticized both
Swingle's conservatism and Tanaka's system with its excessive
splitting. He takes an intermediate position and recognizes
eleven species not considered valid by Swingle and Reece.
These species are indicated in table 3-3
(see footnote). The authors' reasons for their rejection of
these species are stated elsewhere in the text under the discussion of
the several forms whose taxonomic rank is in dispute.
The late R. W. Hodgson made two trips to the Orient and studied the principal Citrus collections in India for nearly a year. He also studied a large number of Citrus
introductions from many parts of the world. He worked in
close association with Tanaka for nearly a year when Tanaka was in the
United States as a Fullbright research scholar. Hodgson
(1961; Hodgson, Singh, and Singh, 1963a, 1963b, and 1963c) published his nomenclature of Citrus which recognized twenty-three Citrus
species of Tanaka's system. Swingle's treatment was
criticized by Hodgson on the basis that it denies species standing to
ancient, well-known, distinctive forms of economic
importance. However, such criteria are not sound reasons for
species standing if they are apomictic and show evidence of their
hybrid nature. It is true that Swingle's treatment may
involve speculation concerning the probable parentage and even error in
proper placing of the form in the attempt to arrive at a natural system
of classification. However, if they are made in an attempt
to understand the natural relationships of biological organisms, do such
errors merit greater censorship than a more artificial system that
names as species forms that are known or probable hybrids, obvious
apomicts, or horticultural forms that can only be perpetuated by
vegetative propagation?
Distinctive or easily recognized form is
not an adequate reason for naming species. The situation in Citrus is somewhat analogous to the situation in Canis domesticus so
well expressed by Dobzhansky (1955): "The longer a species has been
domesticated the more numerous and more diversified are its domestic
varieties. Thus the dog is the most ancient domestic animal,
and has produced the largest number of breeds. Furthermore,
some dog breeds differ so much in appearance, as well as in temperament
and behavior, that it is hard to believe that they all belong to the
same species. Compare the little Chihuahua with a Great
Dane; or an ebullient Fox Terrier with a stolid Saint
Bernard. Nevertheless, all these breeds do belong to one
species, since they are capable of exchanging genes, and often do so,
either directly by occasional hybridization, or via the intermediate
breeds where crossing is impossible because of extreme difference in
size. The dog species has a common gene pool, subdivided, to
be sure, into the gene pool of the various breeds."
Zoological taxonomists consider that those distinctive forms are
"cultivated varieties" not different species. Certainly the
related forms or "breeds" of citrus (the species of Tanaka) have a
common gene pool since they can and do exchange genes through
hybridization.
The study of D. Singh, and C. A.
Schroeder (1962) on the taxonomic and physiological relationships of the
so-called mandarin-lime group of Citrus caused them to conclude: "…the so-called mandarin-lime of Citrus
is a misnomer in that lime parentage is not indicated. The
possibility of mandarin-rough lemon parentage is suggested."
They contend that the binomial Citrus limonia Osbeck should be
employed as a species designation for members of this group.
Determination of the actual parentage of this group is not easy to
establish, but hybrid origin is not only possible, but highly
probable. Apomixis strengthens this probability.
The percent of polyembryony in germinated seeds does not, however,
indicate the degree of apomixis in these varieties. It only
indicates the number of seeds in which two or more embryos were of
sufficient size and strength to emerge on germination and single embryos
are also of apomictic origin in many instances. On the
basis of probable hybridity and apomixis, the binomial of Citrus limonia as a species designation for this group is denied.
The choice as to which of these taxonomic
systems to follow will depend upon the personal viewpoint of the
student of citrus. The biological facts in the case will not
be altered by arguments for or against either system.
However, serious difficulties arise when taxonomists rank apomictically
perpetuated biotypes with sexual species as Heslop-Harrison (1956) has
pointed out. Some taxonomists following such methods have
described as species over 1,100 forms in the hawthorn genus, Crataegus, over 4,000 in the blackberry genus, Rubus, and over 10,000 in the hawkweed genus, Hieracium. It would be a simple matter to embark upon a similar path and describe an astounding number of Citrus
"species," but the multitude of binomials, unnecessarily complicated
keys, and cumbersome system of nomenclature would make the comprehension
of the group difficult indeed.
In the two decades since World War II,
truly remarkable progress has been made in describing the chemical
constituents in citrus tissue. Because of their great
economic importance and adaptability to industrialization, the common
citrus fruits have been the subject of more intensive biochemical
investigation than perhaps any other horticultural crop. As a
result, hundreds of compounds, particularly those found in fruits and
seeds, have been isolated, identified, and in many cases assayed
(Braverman, 1949; Bartholomew and Sinclair, 1941; Sinclair, 1961; U.S.
Dept. of Agriculture, 1962). More recently such research has
been extended to citrus varieties and species of little or no economic
importance and also to some of the near relatives of citrus.
The material summarized in table 3-4 provides an example of this type of research and indicates the great variety of flavonoids found in the genus Citrus
and some relatives. Similar research is in progress on
essential oils (U.S. Dept. of Agriculture, 1962; Stanley, 1963a; Scora, 1966; Scora, et al., 1966; Scora and Newman, 1967; Scora and Torrisi, 1966), coumarins (Stanley, 1963b),
carotenoids (Yokoyama and White, 1965), limonoids (Dreyer, 1965), and
other compounds found in leaves, fruits, or seeds of the Rutaceae
family.
In time the pattern distribution of some
of these compounds may prove to be distinctive within certain genera,
species, or other groupings. Such chemotaxonomic
considerations, when added to the classic morphologic and cytogenetic
bases of classification, should contribute toward a more penetrating
insight into the species problem of citrus.
A key to the subgenera and species of Citrus is presented.
Subgenus Citrus
Subgenus Eucitrus Swing. in Webber & Batchelor, Citrus Indus. 1:395. 1943.
Pulp-vesicles with few and minute, or
sometimes no, oil droplets (never containing acrid oil); petioles
wingless or narrowly winged, or, if broadly winged, then never 3/4 as
broad as the leaf blades; flowers large and fragrant; stamens cohering
in bundles.
The genus Citrus is divided into two very distinct subgenera, Citrus and Papeda, easily distinguished by leaf, flower, and fruit characters. The subgenus Citrus includes all the commonly cultivated species of Citrus,
all of which have pulp-vesicles filled with pleasantly acid, subacid,
or sweet juice, free, or almost free, from droplets of oil.
On the contrary, none of the species of Citrus belonging to the subgenus Papeda
have edible fruits, as the pulp-vesicles have dense aggregations of
droplets of acrid oil that form an axile column and usually give the
juice a very disagreeable, acrid, bitterish flavor.
In the course of
a comparative study of the vascular traces of the flowers of all
obtainable genera of the orange subfamily, Tillson (1938, pp. 21 and 30;
also Tillson and Bamford, 1938, pp. 788 and 790) brought to light a
striking difference between the species of Citrus belonging to the subgenus Citrus and those classed here in the subgenus Papeda. The commonly cultivated species of Citrus, the sweet orange, the mandarin, the grapefruit, the lime, and the lemon, all belonging to the subgenus Citrus,
show "not only fusion of the sepal midrib with the lateral petal
bundles [as is usual in the tribe Citreae], but also fusion of the
lateral sepal bundles with the petal midrib. When the petal
midrib reaches its position beneath the petal base, one or more branches
from it continue into the base of the calyx, forming the lateral sepal
bundles." On the contrary, Tillson found that the species of
Citrus belonging to the subgenus Papeda showed no fusion of the lateral sepal bundles with the petal midrib (this was true even of C. ichangensis, which differs from the other species of the subgenus Papeda in having large flowers, much like those of the species of the subgenus Citrus). In this character of its floral anatomy the subgenus Citrus differs not only from the subgenus Papeda, but also from all the other genera, Fortunella, Eremocitrus, Poncirus, Clymenia, and Microcitrus, all closely related to Citrus, that comprise the True Citrus Fruit Trees.
1. Citrus medica L. Sp. Pl. 2:782. 1753. Citrus tuberose Mill. Gard. Dict. ed. 8. 1768; C. odorata Roussel, Fl. Calvados 194. 1796; C. fragrans Salisb. 1796; C. cedra Link, 1831; C. cedratus Raf. 1838; C. crassa Hassk. 1844. Illus. Risso & Poiteau, Hist. Nat. Orang. pls. 96, 97, 99, 100 (all col.). 1818-1822; Bentley & Trimen, Med. Pl. 1:pl. 53 (col.). 1880; Swingle, in Bailey, Stand. Cycl. Hort. 2:779, fig. 971. 1914; and many others.
Type.—Wanting, but plant seen and studied by Linnaeus.
Distribution.—China and India southward; cultivated in many subtropical regions.
Common name.—Citron.
A shrub or small tree of irregular habit
of growth; twigs angled and purplish when young, soon cylindrical,
glabrous, with stout, short, single spines in the axils of the leaves;
leaves glabrous, elliptic-ovate or ovate-lanceolate, bluntly pointed or
rounded at the tips, cuneate or rounded at the base, margins serrate;
petioles short, wingless or narrowly margined, not clearly articulated
with the leaf blade; inflorescences short, few-flowered racemes; flower
buds large, purplish; flowers perfect or male by more or less complete
abortion of the pistil; petals 5, pinkish on the outside; stamens very
numerous, 30-40 or even 60 as found by Webber (1923, pp. 112-20); ovary
large, bulged, cylindrical, with 10-13 locules, tapering into the thick
style, which is sometimes persistent; fruit large, oblong or oval,
surface smooth or more often rough and bumpy, fragrant, yellow when
ripe, rind very thick, segments small, filled with pale greenish
pulp-vesicles with acid or sweetish pulp; seeds numerous, small, 9-10 X
4-5 X 3-4 mm, pointed at the base, smooth; embryo white.
(See Hodgson's description of the cultivated varieties of citron in this work.)
The citron was the first citrus fruit to
reach the Mediterranean region. Apparently it was introduced
to the eastern Mediterranean area following the invasion of Persia by
Alexander the Great about 325 B.C. Theophrastus (writing
about 310 B.C.) called the citron the Median or Persian
apple. He said that it was inedible but very fragrant and a
remedy for rheumatism and sore mouth, as well as a repellent to drive
away moths. Engler stated (1931, p. 338): "Since the fruits
had the same uses as the wood of the Sandarak tree, Callitris quadrivalvis, the [ancient] name of this wood 'Citrus' was transferred to the fruit as Mala citrea."
This renaming of the Median apple as the Citrus apple led to the
transfer of the name "Citrus" first to the citron and later to other
citrus fruits.
The native home of the citron has not
been determined with certainty. The citron is commonly
supposed to be indigenous to India but J. D. Hooker, who said (1875, p.
514) that he had no doubt about the citron's being truly wild when he
found it growing "mainly on dry sunny slopes [in Sikkim] totally
unsuited for any kind of cultivation…," later came to doubt its being
indigenous. Bonavia (1888, p. 70) stated: "I am still in
doubt whether it [the citron] is indigenous in India. It
does not appear to have any ancient Sanskrit name and the number of
varieties, if they are variations, on the western seacoast is
suggestive. It is curious that they should be found in the
area which came most in contact with foreigners."
The citron has been grown since ancient
times in China, but Chi Han, minister of state under the Emperor Hui Ti,
in a work written about 300 A.D. (Nan fang ts'ao mu chuang)
mentioned the arrival, in 284 A.D., as tribute to the Chinese Emperor,
of 40 Chinese bushels of citrons from Ta-ch'in (a name usually meaning
the Roman Empire). He stated: "…the Barbarians value the
citron very highly. It is aromatic and its flesh is very
thick and white…" This early Chinese record of the citron
would indicate that it was not indigenous to China but had been
introduced from the West.
The early advent of the citron in Media
and Persia, and its subsequent slow penetration into India and China,
could be explained easily if the citron should prove to be a native of
southern Arabia. The bael fruit of India, Aegle marmelos, has no close relatives in Asia, but three closely allied genera, Aeglopsis, Afraegle, and Balsamocitrus, are found in Africa. Citropsis, an African genus of the Near-Citrus Fruit Trees closely related to the Asiatic genus Atalantia,
has eleven species. It would not be surprising to find
midway between India and Africa, in some mountain oasis within the
tropical zone in Arabia, the citron growing in a wild state.
Over a century ago Wellsted (1838, vol. 1, pp. 126-52) found gardens in
the Jebel Akhbar Mountains (150 km southwest of Mascat) where grapes
grew abundantly; also "pomegranates, citrons, almonds, nutmegs and
walnuts with coffee bushes." Over thirty years ago Bartram
Thomas (1932, map, p. 101) explored thoroughly the Qara mountain range,
about 1,100 km farther to the southwest, and found it to be "an Arcadia
of luxuriant forests that clothe steep mountains with perennial
streams." In these mountains, situated in a summer rain belt
along the coconut-fringed shores of the Arabian Sea, Thomas found
giant, large-fruited wild fig trees and "wild-growing, bitter, limes"
fruiting abundantly, as well as an extensive growth of frankincense
trees at elevations of from 2,000 to 2,500 feet above sea
level. Search should be made in this region, between eastern
Hadhramaut and Oman, for the native home of the citron.
The gradual increase in use of the citron
can be traced in early literature. Theophrastus, writing at
Babylon about 310 B.C., said the citron "was not eaten."
Plutarch, writing between 81 A.D. and 96 A.D., stated that "many
substances which in the past people would neither taste nor eat, are
considered today as very agreeable.…Shall we mention the cucumber, the
melon, the Median apple, and pepper?" (Tolkowsky, 1938, p.
91). By the second century the epicurean Apicius Caelius
could recommend the following dishes as being exceptionally delicate:
(1) the white inner part of the peel of citron made up into a salad, and
(2) small pieces of citron peel served with fish mixed with herbs,
vinegar, oil, and spices (Tolkowsky, 1938, p. 59). Before
long citrons had become a prized article of food in Rome, and in 301
A.D. the records show that their sales prices were officially fixed by
Diocletian at values ranging from twelve to sixteen times the price of
melons.
A method of candying citron peel was
finally discovered in the Mediterranean region. This
involved the softening and clearing of the peel, before in was candied,
by fermentation in sea water through the addition of a mixed culture of a
yeast and a bacillus. Candied citron peel ultimately
supplanted almost completely the use of fresh peel. However,
as the fresh citron peel, like that of lemon and orange, contains
hesperidin (Penzig, 1887, p. 286), it is probable that it will prove to
be a good source of vitamin P because of its thick mesocarp, in which
the hesperidin is found. The peel should be tested for the
making of "citrin" (see also table 3-4 and below).
1a. Citrus medica var. sarcodactylis (Noot.) Swing. Pl. Wilson. 2:141. 1914. Citrus sarcodactylis Noot. Fleurs, Fruits, Feuill. Java 1:pl. 3. 1863. Illus. Nooten, loc. cit., pl. 3; Swingle, in Bailey, Stand. Cycl. Hort. 1:781. 1914.
Type.—Lacking in Linnean Herbarium.
Distribution.—Widely cultivated in China, Japan, Indo-China, and India.
Common name.—Fingered citron.
Like the species except in the fruit,
which is split into a number of finger-like sections.
Usually pulp is lacking, or if present is very scanty.
The fingered citron is well known and
highly esteemed for its fragrance and beauty in China and Japan, where
it is called "Buddha's Hand Citron" (Fo Shou kan in Chinese, Bushu-kan
in Japanese). It is used by Chinese and Japanese for
perfuming rooms and clothing. It is also grown as a dwarf
plant, of which good fruiting specimens are highly prized for ornamental
purposes.
1b. Citrus medica var. ethrog Engl. Die Nat. Pflanzenfam. 19a:338. 1931.
Type.—Europe (Engler?). Herb. Bot. Mus., Berlin-Dahlem.
Distribution.—Western Asia and Mediterranean countries; known only in cultivation.
Common name.—Etrog citron.
Fruits small, ellipsoid to fusiform,
rough, with a nipple ending in the persistent style with the persistent
stigma.
The "Etrog" of the Jews, used in the
Feast of Tabernacles, is not mentioned in the Bible. It
probably did not reach Palestine until after the time of Alexander the
Great and was not used by the Jews in fulfilling the prescriptions as
given in Leviticus 23:40. Immanuel Löw (1924, p 286) stated that its use had been recorded from the time of Alexander Jannaeus (104-78 B.C.).
On the basic of the detailed
prescriptions governing the character of the "Etrog" suitable for use in
the Feast of Tabernacles, it is highly probable that the present-day
Etrog is a survival of an ancient form of the citron, perhaps much like
the original form of the species from which the ordinary citron has been
developed by selection.
2. Citrus limon (L.) Burm. f. Fl. Ind. 173. 1768. Citrus medica var. limon L. Sp. Pl. 2:782. 1753; Limon vulgaris Mill. 1768; Citrus limonum Risso, 1813; C. medica var. limonum Hook. f. Fl. Brit. Ind. 1:515. 1872. Illus. Loiseleur-Deslongchamps, Nouv. Duhamel 7:pl. 28. 1818; Risso & Poiteau, Hist. Nat. Orange. pl. 70 (col.). 1818-1822; Hayne, Arzn. Gew. 11:pl. 27. 1830; Bentley & Trimen, Med. Pl. 1:pl. 54. 1880; Ford, Bot. Gaz. 104:288-305. 1942; and many others.
Type.—Europe? (L.?). Herb. Linn. in Linn. Soc. London.
Distribution.—Southeastern Asia (?); widely cultivated in all subtropical countries.
Common name.—Lemon.
Small thorny trees, young leaves and
flower buds reddish; leaves pale green, long-ovate, pointed at the tip,
margins serrate or subserrate; petioles narrowly winged or margined,
plainly articulated with the leaf blade; flowers reddish-tinted in the
bud; petals white above, purplish below; stamens numerous, 20-40; ovary
subcylindric or barrel-shaped, tapering into the thick deciduous style;
fruit oval with a broad, low apical papilla, with 8-10 segments; peel
yellow when ripe, rather thick, prominently glandular-dotted; seeds
small, ovoid, pointed, smooth, white within.
The origin of the lemon is a mystery. Tanaka (1929b,
p. 342) suggests that it was not introduced to China until the Sung
Dynasty (760-1297 A.D.), and it is still rare in India (according to
Biraghi, 1935). It was actively spread in the Mediterranean
region by the Arabs about 1000 to 1200 A.D. Like the sour
orange, it became widely and favorably known as a medicinal
agent. According to Glidden (1937, p. 382), the lemon was
first described in detail by Ibn-Jami, a physician at the court of
Saladin (1171-1193 A.D.), in a treatise on the medical uses of the lemon
(now lost; parts, however, have been preserved in
quotations). The lemon was considered by Linnaeus to be a
variety of the citron (C. medica) and obviously closely related
to it. Probably the lemon should be considered as a
satellite species of the citron; possibly it may prove to be of hybrid
origin, perhaps having the citron and the lime for parent
species. As is true with the grapefruit, it is difficult to
explain the origin of the lemon as a hybrid, as it crosses readily with
other species of Citrus and yet, when self-pollinated, reproduces
itself from seed with only small variations. For this
reason it is left here as a distinct, but probably satellite, species of
Citrus.23
The glucoside hesperidin
was found in fruits of the lemon tree by Pfeffer (1874, p.
529). A comprehensive account of the biochemistry of the
glucosides, organic acids, sugars, vitamins, essential oils, and other
constituents found in the lemon is given in The Lemon Fruit by Bartholomew and Sinclair (1951) and in U.S. Department of Agriculture Agricultural Handbook 98 (1962).
The true lemon is of recent introduction
and is still very rare in southern China, as was shown by Kwok Wa-shau,
who in 1921 and 1922 made, under Swingle's direction, for the Bureau of
Plant Industry (now encompassed by the Agricultural Research Service) a
detailed survey of all the citrus fruits cultivated or found growing
wild in the vicinity of Canton. The so-called white lemon, pak ning-mong in Cantonese, and the red lemon, hung ning-mong,
both of which grow commonly in southern China, are not true lemons, but
are hybrids, perhaps between the lemon and the mandarin orange (see below).
The origin of the lemon is still doubtful
unless it proves to be a hybrid or sport of the so-called lemon of
India. The rough lemon, commonly used as a rootstock in the
United States, is apparently widely naturalized or possibly indigenous
in India and Pakistan, where it is called jambhiri. According
to Bonavia (1888-1890, p. 61), it was mentioned by the Emperor Baber in
his memoirs, composed in 1519 A.D. (Bonavia figured the fruit in pls.
131, 132). Hodgson (1937, p. 513) reported finding in India a
form of jambhiri "indistinguishable from our Florida rough
lemon." It grows in a seminaturalized state along the Mazoe
River in Southern Rhodesia, South Africa, where it is called the Mazoe
lemon. The rough lemon has been found to show a very high
percentage of nucellar embryos, which would indicate a hybrid
origin. True lemons, on the contrary, show only a small
proportion (10 to 15 per cent) of nucellar embryony.
HYBRIDS OF THE LEMON
Lemonange ? [Citrus limon X C. sinensis ?].
The only hybrid of this supposed
parentage that has come into culture in the United States is the Meyer
lemon, grown as a potted plant in Peking, China, and introduced into
this country in 1908 by the late Frank N. Meyer, then agricultural
explorer of the Foreign Plant Introduction Service of the former Bureau
of Plant Industry. It was figured and described by McKee
(1927, pp. 218-21, text figs. 48, 49); see also Traub and Robinson
(1937, p. 751). It is probably a hybrid between the lemon
and some other species of Citrus.
Lemonimes [Citrus limon X C. aurantifolia].
These hybrids, made by safeguarded,
cross-pollinations, are intermediate between the two parent
species. The best known of these hybrids, the Perrine lemon (C. aurantifolia 'Mexican' X C. limon 'Genoa'), is noteworthy in having high resistance to lemon scab (caused by Elsinoë fawcettii) and also to lime withertip (due to Gloeosporium limetticolum),
the worst diseases afflicting the two parent species. The
Perrine lemon is described and figured in Swingle, Robinson, and Savage
(1931, p. 15, pl. 10), in McLennan (1937, 1 text fig. and col. front
cover), and in Traub and Robinson (1937, p. 781, fig. 15).
Lemandarins [Citrus limon X C. reticulata ?].
Probably the Otaheite orange, the hung ning-mong, or "red lemon" of the Chinese of Canton, and the lemon called pak ning-mong
or "white lemon" are both hybrids of this character, possibly complex
hybrids. Tanaka has shown (1925, pp. 107-26, and 1933b, col. pl. 8) that the name Citrus limonia Osbeck belongs or was assigned to one of these hybrids (not to the hung ning-mong, as he supposes, but to the pak ning-mong),
but such hybrid fruits propagated artificially by man cannot be
considered as true taxonomic species. They arose doubtless
as garden hybrids in southern China through crosses and pollinations
effected by insects between the lemon, possibly introduced by the Arabs,
and the native mandarin orange.
Rumphius (1741, vol. 2, p. 101, pl. 26,
fig. 2) figured a lemon called Lemon Martin, grown in the East Indian
Archipelago by Europeans, that is almost certainly a hybrid between a
true lemon, probably brought in by the Portuguese, and some other
species of Citrus (possibly C. grandis or C. hystrix);
nevertheless it is called a lemon by the Europeans who live in the East
Indies and by other Europeans. The same thing seems to have
happened in southern China to the true lemon, probably transported
there by the Arabs and then degenerated by hybridization.
3. Citrus aurantifolia (Christm.) Swing. Jour. Wash. Acad. Sci. 3:465. 1913. Limonia aurantifolia Christm. in L., Pflanzensyst.…nach d. Houttuyn. 1:618. 1777; Limonellus sive Limon Nipis Rumph. Herb. Amboin. 2:107. 1741; Limonia acidissimia Houttuyn. (non L.) Natuurl. Hist. 2(2):444. 1774; Citrus lima Lun. 1814; C. acida Roxb. 1832; C. spinosissima Meyer 1818; C. notissima Blanco, 1837; C. limonellus, Hassk. 1848; C.medica var. acida Hook. f., Curtis' Bot. Mag. 3 ser. 40:pl. 6745 (col.). 1884. Illus. Rumphius, loc. cit. pl. 29; Merian, Metam. Insect., Surinam. 17, pl. 17 (col.). 1705; Hooker f. loc. cit. pl.
6745 (col.); Bonavia, Cult. Orang. Lem. India Cey., Atl. pls. 228, 229.
1890; Hume, Cult. Citrus Fruits 19, 20, figs. 18, 20. 1926; Ochse,
Fruits Fruitcult. Dutch East Ind. pl. 44 (col.). 1931; European
iconographies of Citrus usually have misleading illustrations of this species!
Type.—East Indian Archipelago, Amboyna, no type preserved; based on Rumphius' description and plate and on Merian's plate.
Distribution.—East Indian Archipelago; widely grown in all subtropical regions.
Common name.—Lime.
A small tree with rather irregular
branches; twigs with short, stiff, very sharp spines; leaves small,
5-7.5 cm long, elliptic-ovate or oblong-ovate, obtusely pointed at the
tip and rounded at the base, margins crenulate, pale green, petioles
narrowly winged, spathulate; inflorescences axillary, short, lax racemes
of 2-7 flowers (rarely single); flowers small, white in the bud, calyx
cupulate, 4-5 lobed; petals 4-5, 8-12 X 2.4-4 mm; stamens 20-25; ovary
depressed, globose, with 9-12 segments, not merging into the style but
clearly set off from it; style soon deciduous; stigma depressed,
globose; fruits small, oval or subglobose, often with a small apical
papilla, greenish-yellow when ripe; peel very thin, prominently
glandular-dotted; seeds small, oval, white inside. (See
Hodgson's descriptions of limes in this work [excluding the Rangpur and Kusaie varieties, which belong not to this species but probably to C. reticulata, or else are hybrids of it with the lime].)
The lime is apparently indigenous in the
East Indian Archipelago. From there it has spread by human
help to the Asiatic mainland and to many other tropical or subtropical
regions of the world. It is a distinct species, not closely
related to any other species of Citrus. However, limes hybridize freely with other species of Citrus and many such hybrids are found in the East Indies. The Tahiti lime (see chap. 4, this work),
which is widely grown in Florida and California, was found by Bacchi
(1940) to be in a triploid cytonomic state; Uphof (1931) had already
discovered that it produces no pollen grains or viable ovules.
HYBRIDS OF THE LIME
Lemonimes [Citrus aurantifolia X C. limon].
These hybrids, looking much like lemons, are discussed above.
Limequats [Citrus aurantifolia X Fortunella japonica, or F. margarita].
These lime-like hybrids are discussed under Fortunella.
4. Citrus aurantium L. Sp. Pl. 2:782. 1753. Aurantium acre Mill.Gard. Dict. ed. 8. 1768; Citrus florida Salisb. 1796; C. vulgaris Risso, 1813; C. bigarradia Loiseleur-Deslongchamps, 1818; C. bigaradia Risso & Poiteau, 1818-1822; C. amara Link. 1831; C. karna Raf. 1838; C. communis Le Maout. & Decaisn. 1868; C. aurantium var. bigaradia Hook. f. 1875. Illus. Risso & Poiteau, Hist. Nat. Orang. pl. 30 (col.). 1818-1822; Berg & Schmidt, Darst. Beschr. Off. Gew. 3:pl. 31. 1861; Bentley & Trimen, Med. Pl. 1:pl. 50. 1880; Tschirch & Oesterle, Anat. Atl. Pharm. pls. 69, 70. 1898.
Type.—Europe ? (Linnaeus ?). Herb. Linn. in Linn. Soc. London.
Distribution.—Southeastern Asia; widely cultivated in all subtropical regions.
Common name.—Sour or Seville orange; bigarade.
A medium-sized tree up to 10 m high, with
a rounded top; twigs angled when young, with single, slender spines,
often short, or stout spines up to 5-8 cm long on rapidly growing
shoots; leaves medium-sized, ovate, bluntly pointed at tip, broadly
rounded to cuneate at base; petioles 2-3 cm long, rather broadly winged,
often 1.2-1.8 cm wide at top, but sometimes narrower, 1 cm or less,
narrowing rapidly to the wingless base; flowers large, very fragrant
with oil of neroli; 5-12 per cent male (staminate only); fruits
subglobose, usually slightly depressed at both base and top, peel thick,
with a rather rough surface, becoming brilliant orange with a reddish
tint at maturity; locules 10-12, filled with sharply acid pulp and
numerous seeds; fruit becoming hollow at center as it matures, and then
able to float in water. (See Hodgson's account of the
cultivated varieties of the sour orange in chap. 4 of this work).
This species was introduced into the
Mediterranean region from the East and for many centuries was the only
orange known to Europeans. During this long period of
culture it became very well known and much appreciated as a medicinal
agent; the fruits were used for flavoring and for marmalade, and the
flowers for perfumery. It was the orange of late medieval
Europe. Good high-flavored varieties of the sweet orange, C. sinensis,
did not reach Europe from southeastern Asia until the fifteenth
century. From that time on there was more or less confusion
over the name of the sour orange. The pharmacologists
persisted in calling it C. aurantium and the citrologists, then the botanists, called it C. bigaradia. Many
botanists considered both the sour and the sweet orange as merely
varieties of a single species. As a matter of fact, the sour
orange (C. aurantium) and the sweet orange (C. sinensis) are very distinct botanical species, not merely cultivated varieties of one species.
The chief morphological differences are
as follows: In the sour orange the petioles are much more broadly winged
than in the sweet, and the leaf blades are narrower and more acutely
pointed at the apex, and less rounded and more cuneate at the
base. Ruggieri has shown (1935) that the petioles of the
sour orange are much the longer, averaging 25.89 mm, whereas those of
the sweet orange average only 15.91 mm; in other words, the sour orange
petioles average 63 per cent longer than those of the sweet
orange. The fruits of the sour orange are of a brighter
orange color and have a rougher peel; moreover, in the sour orange the
oil glands are situated beneath minute sunken areas in the peel, whereas in the sweet orange the tissue covering the oil glands is often convex.
Uphof reported (1932, pp. 133-35, fig. 4)
that he found no male flowers on several cultivated varieties of the
sweet orange (C. sinensis), but that he did find from 5 to 12 per cent of male flowers on the sour seedling oranges of Florida (C. aurantium).
The sour orange, according to Uphof, "probably is very close to the
sweet orange but from the standpoint of the production of male flowers
constitutes a transition, so to speak, toward the lemons, limes and
citrons." Uphof found no male flowers on cultivated
varieties of the grapefruit (C. paradisi). Many trees of the Dancy tangerine (C. reticulata)
showed no male flowers (one small tree overloaded with a very heavy
bloom had one single male flower among the thousands
examined). Tangelos (hybrids of C. reticulata with C. paradisi) also showed no male flowers.
In view of these facts, it is clear that
the occurrence in appreciable numbers of male flowers in C. aurantium constitutes an important differential character separating this species from C. sinensis.
The ethereal oil in the leaves, flowers,
and fruits of the sour orange is of very different odor than that in the
sweet (more agreeable and aromatic in the sour orange) and has a
different composition. Also the oil recovered from the
petals of the sour orange, neroli oil, finds a different use in
perfumery and has a higher value than that of sweet orange
flowers. This oil, considered by perfumery experts to be
"indispensable to finer perfumery," is said to owe its high value to
small amounts (only 0.4 to 1.0 per cent) of "a nitrogenous compound of
exceeding fragrance," methyl anthranilate, NH2 · C6H4 · COOCH3
(see Gildemeister and Hoffmann, 1922, pp. 93 and 96; and Finnemore,
1926, pp. 436-41). This remarkable substance is not found in
the oil extracted from the petals of the sweet orange (Theulier,
1902). The pulp of the sour orange is intensely sour, with a
bitterish aftertaste, in contrast to the sweet, agreeable flavor of the
sweet orange. Furthermore, the peel of the sour orange,
which is official in the British Pharmacopœia (the peel of both the sour
and the sweet orange is official in the U.S. Pharmacopœia), contains
three glucosides, according to Tanret (1886, p. 518): (1) 4 to 30 parts
per 1,000 of isohesperidin (= naringin ?), having the same percentage
composition and the same rotary polarization as hesperidin but a bitter
taste (hesperidin of the sweet orange is tasteless) and a very different
solubility; (2) 15 to 25 parts per 1,000 of aurantamarin (to which, so
Tanret asserts, most of the bitter taste of the sour orange peel is
due), differing slightly in composition and in solubility from both
naringin (?) and hesperidin; and (3) from a mere trace to six parts per
1,000 of hesperidin. In the sweet orange only this last
glucoside, hesperidin, is found, but it is present in much larger
quantities than in the sour orange.24
The sour orange also shows physiological
differences from the sweet orange. It stands winter cold
better and has almost complete immunity to the foot rot, or mal di
gomma, so destructive to the sweet orange in some
localities. However, the sour orange is severely attacked by
the scab fungus, Elsinoë fawcetti, which does not attack the sweet orange.
Besides the morphological, chemical, and
physiological differences mentioned above, there are further anatomical
difference discovered by Ruggieri (1935) between the sour and the sweet
orange in the separative layer of articulation that lies between the
petiole and the leaf blade, which may be summed up as follows: (1) The
pith in the lower articulation joint where the petiole joins the twig is
much more flattened from the top to the bottom in the sweet orange than
in the sour. In the sour orange the ratio of the pith to
the woody cylinder averages 1:1.4, measured in a horizontal direction,
and 1:2.2, in a vertical direction, whereas in the sweet orange the
ratio of pith to woody cylinder is 1:1.5 horizontally (about the same as
in the sour orange) and 1:4.5 in the vertical (dorsiventral) direction,
or only half as thick as the pith of the sour orange
petiole. (2) The cells of the interior layers of the
cortical parenchyma of the upper articulation joint where the petiole
joins the leaf blade are isodiametric and are 12 to 20.5 mu in diameter in the sour orange but are 20 to 27 mu
in diameter in the sweet orange, or nearly one-half larger than in the
sour orange. (3) The pericycle fibers that form a more or
less interrupted sheath around the woody cylinder are strongly thickened
in the sour orange but are little thickened, if any, in the sweet
orange.
B. Miyazaba, S. Matsubara, and T. Kawaida
(1928, p. 189, figs. 4, 5) have also found other anatomical characters
that separate the sour orange from the sweet. Comparing the
common sour orange (kaisei-to) of Japan with the Washington navel orange (tento) in leaf structure, they found that the sour orange leaf is thin (197 to 274 mu, the average of the ten measurements being 243.38 mu), whereas the sweet orange leaf is about 11.1 per cent thicker (247 to 334 mu, the average of the ten measurements being 270.33 mu).
The two layers of palisade tissue are about the same thickness in the
two species, but the spongy tissue shows a wide variation, being only
148 to 189 mu thick in the sour orange leaf (the ten measurements averaging 167.28 mu) but ranging from 165 to 231 mu in the sweet orange leaf (the ten measurements averaging 197.51 mu),
or nearly 17 per cent thicker. They also found that the
number of stomata is somewhat greater in the sweet orange epidermis than
in that of the sour orange, averaging 23.44 in the microscope field of
vision for the sweet orange and 20 for the sour orange, or 17 per cent
more for the sweet orange.
In view of this array of anatomical,
physiological and chemical differences between the sour and the sweet
orange it is obvious that they are distinct species even if the gross
morphological differences between them are small.
VARIETIES AND MUTATIONS OF THE SOUR ORANGE
Hodgson has given in this work an account of the forms of the sour orange known in the United States, including the Bittersweet, with sweet fruits; the Paraguay, with subacid fruits; and the Bergamot,
grown in Italy for the manufacture of bergamot oil from the
fruits. These three varieties are of unknown origin and
opinions with respect to whether they are mutations of the sour orange,
like variety myrtifolia, or hybrids. Experimental hybridization would probably settle the question promptly.
The orangeries of Europe, which came into
vogue early in the fifteenth century and for two centuries were among
the most prized possessions of everyone who could afford one, were
filled with every form of citrus that could be found, among them many
forms of the sour orange. Tolkowsky (1938, p. 186) observed:
"However, it was the sixteenth and part of the seventeenth century…that
gave citrus trees, both in theory and practice, their final status as
an element of the first importance in the Italian garden."
He also stated that the first orange house or "orangery" in northern
Europe, where citrus could not be grown out of doors, was built by order
of Charles VIII, king of France, in his own château at Amboise after
his famous expedition to Italy in 1494 and 1495. "The
example set at Amboise was soon followed in other royal castles and in
those of many members of the nobility." The most famous
orangeries, according to Tolkowsky (pp. 200, 209), were those built for
Louis XIV at Fontainebleau and Versailles and finally, in 1674, the one
for Madame de Montespan at Clagny, where by 1675, so Madame de Sévigné
reported to her daughter, "there is a whole forest of orange-trees in
huge boxes."
In 1818-1822, Risso and Poiteau in their famous folio work, Histoire naturelle des orangers,
published descriptions and colored plates in natural size of 23
varieties of sour oranges called bigarades. Of these, eleven
had already been named, described, and figured by Ferrari in his great
work the Hesperides, published in 1646. A glance at
these plates suffices to show what a wealth of forms, both normal and
teratological, were grown in Europe. Many of these forms are
still to be found in the citrus collections of the Old World, and a few
new forms have appeared in recent works on the European varieties of
citrus fruit trees (Riccobono, 1899, pp. 141-83; lnzenga, 1915, pp.
19-26; Galli, 1928, pp. 10-13; and others). A striking new
strain of the sour orange, named the Oklawaha, was originated
within the United States. It has large fruits, 7.5 to 10 cm
in diameter with a rind 6 to 10 mm thick, that are rich in pectin,
making it an excellent marmalade variety (see Swingle, Robinson, and
Savage, 1932, pp. 9-10; and Traub and Robinson, 1937, pp. 782-83).
The Trabut variety of sour orange
(named in honor of L. Trabut, who brought together at Maison Carrée,
Algeria, early in the twentieth century, a very fine collection of
cultivated varieties of citrus) is a European strain bearing normal
bitterish-sour fruits but differing from all other published
descriptions or figures of sour oranges in having very large, obdeltoid
petioles, much broader (2 to 3 cm) than those of typical sour orange
leaves. It was introduced into the United States by David
Fairchild in 1925, and distributed as F.P.I. No. 63550. It,
like the Oklawaha variety just noted, is a strain of sour orange very
readily recognized by an easily seen morphological character.
The Daidai is a cultivated variety
of the sour orange common in Japan that differs little from the
ordinary sour orange except in being dwarfish in habit, and having
blunt-tipped leaves and a persistent calyx that continues to grow as the
fruit develops, finally turning yellowish or orange-colored as the
fruit ripens. This variety shows almost complete immunity to
citrus canker in the Philippine Islands, where ordinary sour orange is
very susceptible, as Swingle observed in 1915. The Daidai is
also known in China, where it is grown in Kiangsu and Chekiang
provinces for its flower buds, which are used to mix with tea
leaves. It is likewise grown in Canton, especially in the
famous Fa t’i flower gardens, as a potted plant. Hu (1934,
p. 47) described it as follows:
"After a growth of 5 or 6 years the Tai-tai
[pronounced 'dai-dai'] tree reaches a height of 1 m; its branches grow
sparsely and are of spreading habit; the leaves are elliptical or ovate,
apex obtuse, base rounded; leaf blades are very thick, petioles winged;
leaves are broad and thick. Fruit is compressed-globose,
measures 5.4 X 6.4 cm; peel is of orange red color. Fruit
pulp is in 10 segments, membranes are thick and white; fruit flesh is
light yellow. Seeds ellipsoid, apex cuneate, monoembryonic;
cotyledons white in color; chalaza purple. Fruit juice is
very sour, so the fruits are not fit to eat in their raw
state. They [the Chinese orchardists] gather only the flower
buds of this species which they fire-dry to make a scenting material
for tea leaves."
Hu failed to mention that the Chinese
Tai-tai has enlarged, persistent calyx lobes, but a description drawn up
by Kwok Wa-shau, Swingle's former assistant working at Canton, China,
from plants introduced into Kwangtung Province (about 1915) from
Soochow, Kiangsu Province, reads: "The calyx is remarkably large, being
strikingly different from that of the other species of Citrus, bluish-green in color, the 5 sepals forming a somewhat protruding cup…The rind is extremely thick and the pulp very sour."
The Chinese do not use the Tai-tai as a
rootstock; instead they use the following sorts that grow to a larger
size:
The Vermillion globe sour orange (chu-luan),
which grows to a height of 5 meters and has long, narrow, acutely
pointed leaves. Hu (1934, p. 46) described it as having
compressed-globose fruits, 8 cm long and 9.5 cm wide, with many (30 to
40) seeds. It is used as a rootstock for sweet oranges.
The Leather-head sour orange (p'i-t'ou ch'êng),
which has elliptical leaves, blunt at the tip, small depressed-globose
fruits, 4.4 cm long and 6 cm wide, with rough peel and with numerous
(about 20) seeds. It is used as a rootstock for sweet
oranges at Huangyen, Chekiang Province.
Tanaka, who studied the citrus fruit
trees grown in the coastal regions of China opposite Taiwan, reported
(1932a, p. 29) that the sour orange rootstocks used in Fuchow and
Huangyen "are very different from our [Japanese] Dai-dai."
Probably the sour orange used as a rootstock at Huangyen which Tanaka
mentioned was the form called Leather-head sour orange by
Hu. Tanaka, who is familiar with the sour orange used as a
rootstock in the United States, stated further that "our Daidai…is the
most inferior grafting stock. On the other hand, the sour
orange in the United States and Italy is an excellent grafting stock, as
well as that of Chekiang…"
Benemerito (1938), like Kwok (1922),
found no typical sour orange growing in Kwangtung Province, only the
mutation Tai-tai, which has a large and persistent calyx. He
listed four other varieties that he assigned to Citrus aurantium,
but three of them, which have very narrowly winged petioles, are
probably hybrids, whereas the fourth, which has sometimes broadly winged
and sometimes narrowly winged petioles, was considered by Benemerito
himself as probably a hybrid between the sour orange and a
mandarin. Some of these hybrids are worth testing as
rootstocks.
POSSIBLE ORIENTAL HYBRIDS OF THE SOUR ORANGE
Besides the four varieties from China and Japan, discussed above, that seem to be mutations of C. aurantium,
there are other forms, probably accidental garden hybrids of unknown
parentage. The following are known from Taiwan and Japan:
Hyonkan.
This form has large leaves (13 by 6.5
cm), acute or acuminate at the tip, and small, subglobose (6 cm high, 7
cm wide), thick-skinned fruits with a solid core. The calyx
in the flowering stage has slightly enlarged sepals; these, however, do
not elongate as the fruit grows. Hayata (1919, pp. 27, 28,
text fig. 16) named it Citrus daidai after a nomen nudum of Siebold printed in 1830, but he stated: "It may be [a] hybrid between C. aurantium and C. sinensis."
It is reported as being cultivated in Taiwan and as being much like a
Japanese variety called Kwai-seikan ("very green [sour]
orange"). Certainly no evidence is adduced to show that this
variety merits a species name.
Nanshô daidai.
This is a form found, very rarely,
growing semiwild in the forests of Taiwan in three localities, Nanchwang
(formerly Nanshô), Gaogan and Taitung districts. Tanaka
(1932a, pp. 20-21) stated that the "Nanshô daidai resembles the Daidai [the Japanese form of] Citrus Aurantium
in the shape of the fruits, but the leaves are somewhat similar to the
Naruto-mikan." He went on to say that the fruits are round
in shape with a slight nipple at the apex, have an acid taste like the
Yama-mikan, and have a thick rind like a citron.
The Nanshô daidai differs from the ordinary Japanese Daidai, according to Tanaka (1926d,
pp. 54-58), "in having much longer leaves [blades about 12 by 5 cm],
lanceolate, sharply and gently pointed at the tips, thin, inodorous;
petioles broadly winged; calyx glabrous, fruits flattened, globose, peel
with smaller oil glands, pulp delicate, very sour and more deeply
yellow." In this article the Nanshô daidai was published in
Japanese as Citrus taiwanica Tanaka and Shimada. Tanaka (1926a, p. 345), a month later, published the Nanshô daidai in English as a new species, Citrus taiwanica
Tan., and stated, "at present it seems to have become extremely
scarce." It is by no means clear that this is a good
species; it is probably a hybrid of C. aurantium with some other species of Citrus having
long leaves. Tanaka thought that the "very uniform"
seedlings of this species might "serve as stocks for commercially
semitropic citrus fruits." This very uniformity of the
seedlings may be due to the hybrid nature of the Nanshô daidai, as many Citrus
hybrids yield perfectly uniform seedlings from nucellar buds that
replace the true embryo in the seeds. In a later publication
Tanaka (1933b, p. 172, fig. 138) included a halftone illustration of the type specimen showing flowering twigs; another text figure (1933b, p. 136, fig. 112) illustrates the depressed-globose, thick-skinned fruit, which shows 10 segments.
Yama-mikan ("Mountain mandarin").
Concerning this form, T. and Y. Tanaka
(1932, p. 3) stated: "Yamamikan…is used as a rootstock in Hyûga Province
[in Japan], and it corresponds to the American sour stock in its vigor
and habit."
ACCURATELY SAFEGUARDED HYBRIDS OF CITRUS AURANTIUM
Apparently the only sour orange hybrid
known that was made by properly safeguarded cross-pollination is the
following bigeneric one:
Citradia [Citrus aurantium X Poncirus trifoliata].
This beautifully intermediate trifoliolate hybrid has great vigor and hardiness (see also under Poncirus).
4a. Citrus aurantium var. myrtifolia Ker-Gawl. [John Bellenden] Bot. Reg. 4:text to pl. 346. 1818. Citrus myrtifolia Raf. Sylva Tellur. Mant. 141. 1838; C. sinensis Pers. (non Osb.) Syn. Pl. 2:74. 1807. Illus. Ker-Gawler, loc. cit. pl. 346 (col.); Risso & Poiteau, Hist. Nat. Orang. pl. 50 (col.). 1818-1822.
Type.—England (Ker-Gawl.). Herb. ?
Distribution.—Known only in cultivation: supposed to have been brought from China into the Mediterranean regions in the seventeenth century.
Common name.—Myrtle-leaf orange.
Twigs with very short internodes, usually
1-2 cm long, often without spines; leaves small, about 1/2-1/3 the size
of the normal foliage of the species; fruit small, often about 1/4-1/2
the size of that of the species.
This plant is so strikingly different
from the common orange that Charles Darwin (1868, p. 100) considered it
to be one of the most distinct species of Citrus. He
stated: "…I can adduce another case: the myrtle-leaved orange is ranked
by all authors as a variety, but is very distinct in general aspect: in
my father's greenhouse, during many years, it rarely yielded any seed,
but at last produced one; and a tree thus raised was identical with the
parent form."
The myrtle-leaved variety of the sour
orange probably arises as a mutation of the common form of the sour
orange. Swingle once found at Leesburg, Florida, sprouts of
this myrtle-leaved variety growing from the roots near the base of the
trunk of a very old sour orange rootstock on which a large sweet orange
had grown from a graft. Doubtless this old sour orange was
originally, like the many others found in the same grove, dug up from
under the live oak trees in a hardwood grove on rich soil (hammock)
where sour orange trees grew in a semiwild condition.
One important horticultural race of sour
orange, the chinotto of Italy, belongs to this variety. It
is grown for its small fruits, which are candied.
THE TAXONOMIC PROBLEM OF CITRUS AURANTIUM AND ITS FORMS
Citrus aurantium is unusual and can almost be said to show mimicry of the sweet orange, C. sinensis. It
has required careful search to find morphological differences to
separate the two species; yet they show great differences in their
physiological requirements and limitations, in their graft compatibility
to other citrus fruit trees, in their resistance to disease, and
especially in the chemical composition of their essential oils,
glucosides, etc.
If we admit that the two species are
distinct in spite of their mimicry, we then face the even more difficult
problem of distinguishing the similar-looking but physiologically
diverse forms, whether subspecies, varieties, or strains, found within
the species. Two forms of sour orange so similar as to look
almost identical may have profoundly different values as rootstocks for
the lemon and perhaps for other cultivated citrus fruit
trees. This problem, already bafflingly complex, is further
complicated by the hybrids of C. aurantium, which make an already bad taxonomic situation still worse.
5. Citrus sinensis (L.) Osbeck, Reise Ostind. China 250. 1765. Citrus aurantium [var.] sinensis L. Sp. Pl. 2:782. 1753; Aurantium sinensis Mill. Gard. Dict. ed. 8. 1768; Citrus aurantium Lour. (non L.) Fl. Cochinch. 2:466. 1790; C. aurantium Risso (non L.), Ann. Mus. Hist. Nat. Paris 20:181. 1813; C. aurantium [var.] vulgare Risso & Poit. Hist. Nat. Orang. 33. 1818-1822; C. aurantium [var.] dulce Hayne, Arzn. Gew. 11:pl. 28. 1830. Illus. Risso & Poiteau, loc. cit. pls. 3, 4 (col.); Hayne, loc. cit. pl. 28 (col.); Bentley & Trimen, Med. Pl. 1:pl. 51 (col.). 1880; and many others.
Type.—Europe (Linnaeus), lost ? (no authentic specimen in Linnean Herbarium, fide B. Daydon Jackson [1912, p. 58]).
Distribution.—China, Indo-China, possibly other southeastern Asiatic regions.
Common name.—Sweet orange.
A medium-sized tree with a rounded top
and regular branches; twigs angled when young, usually with slender,
somewhat flexible, rather blunt spines in the axils of the leaves;
leaves medium-sized, pointed at the apex, rounded at the base; petioles
narrowly winged, articulated both with the twig at the base and with the
leaf blade at the tip; flowers in small racemes or singly in the axils
of the leaves, medium-sized; calyx with 5 lobes; petals 5; stamens
20-25; ovary subglobose with 10-13 locules; style slender, clearly
delimited, soon falling; fruits subglobose, oval or flattened globose;
peel thin, tight, not bitter, central axis (pith) solid; seeds
cuneate-ovoid with rough-margined plane surfaces, white inside; embryos
usually numerous, varying greatly in size. (See Hodgson's
descriptions of the cultivated varieties of the sweet orange in this work.)
In 1914, in discussing Chinese species of Citrus, Swingle stated (1914a,
pp. 150-51): "The common sweet orange, often confounded with the sour
or Seville orange, is in fact quite distinct from the
latter. The fruits of the sweet orange have a solid core,
never becoming hollow like that of the sour orange; the petioles are
narrowly winged in the sweet and broadly winged in the sour orange; the
leaves and flowers of the two species have a very distinct
odor. The two species show decided differences in their soil
requirements and in their susceptibility to the attacks of fungous
diseases. Many other minute but constant divergences are
shown between these two oranges in all their organs. These
two plants, then, superficially so similar, are in reality very unlike
and should by no means be united as varieties of one
species." In the discussion above under C. aurantium
is has been shown that many anatomical differences between the sweet and
the sour orange have recently come to light, differences that go far to
show that these are in reality very distinct species that happen to
possess certain superficial resemblances concealing many profound
differences.
Citrus sinensis is probably native
to southeastern Asia, in northeastern India or, more likely, in
southern China and Indo-China. It has been so widely
cultivated for so long that it is no longer known in a truly wild
condition.
Tolkowsky (1938) theorized that the sweet
orange first appeared in Roman gardens as early as the first century
A.D., eventually disappearing in the barbaric invasions. The
sweet orange mentioned in literature of the fifteenth century appears
to have reached Europe over the Genoese trade route, followed by
superior varieties brought around the Cape of Good Hope by Portuguese
navigators in the sixteenth century.
Before the advent of the sweet orange
into the Mediterranean regions, citrus fruits were esteemed there for
medicinal use, but the introduction of this delicious and beautiful
fruit aroused an intense interest in Citrus and led many people
of means to build orangeries wherein they grew all sorts of citrus
fruits. Everyone in Europe heard of these wonderful
fruits. By the middle of the seventeenth century (1646)
Ferrari had written his Hesperides, a beautifully illustrated
account of the citrus fruits then known. Around this was
woven the story of Hercules, taken from Greek mythology, who was
supposed to have found oranges when he gathered the golden apples of the
Hesperides.
The fruits of
the sweet orange contain a glucoside, hesperidin, which was discovered
by Lebreton in 1828 but was first recognized as a glucoside by A. Hilger
(1876) and E. Hoffmann (1876). It is allied to, but
different from, the naringin of the pummelo and the grapefruit, the
aurantamarin of the sour orange, and the ponciridin of trifoliate orange
(see table 3-4).
Much interest was aroused by the discovery of "citrin," or vitamin P,
related to hesperidin, in the juice and peel of the lemon (and sweet
orange) by Szent-Györgyi and his colleagues (see Rusznyák and
Szent-Györgyi, 1936; Armentano et al., and Szent-Györgyi, 1936;
and Rosenberg, 1942). Further information on the composition
and biochemistry of the sweet orange may be found in Sinclair (1961)
and the U.S. Department of Agriculture's Handbook No. 98 (1962).
HYBRIDS OF CITRUS SINENSIS
Tangors [Citrus sinensis X C. reticulata].
These hybrids, which look much like the
sweet orange, bear orange-like fruits often of high quality.
They are discussed under C. reticulata.
Citranges [Citrus sinensis X Poncirus trifoliata].
See under Poncirus.
Citrangors [Citrus sinensis X (C. sinensis X Poncirus trifoliata)].
See under Poncirus.
Citrangequats [(Citrus sinensis X Poncirus trifoliata) X Fortunella japonica, or F. margarita].
See under Fortunella.
Citrangedins [(Citrus sinensis X Poncirus trifoliata) X (Citrus reticulata var. austera ? X Fortunella sp.)].
See under Fortunella.
Citrangeremos [(Citrus sinensis X Poncirus trifoliata) X Eremocitrus glauca].
See under Eremocitrus.
6. Citrus reticulata Blanco, Fl. Filip. 610. 1837. Citrus nobilis Andrews (non Lour.), Bot. Repos. 9:pl. 608. 1809; C. nobilis var. major Kerr, Bot. Reg. 3:pl. 211. 1817; C. deliciosa Ten. Ind. Sem. Hort. Neap. [9]. 1840; C. nobilis var. genuina Tan. Bot. Mag. Tokyo 26:204. 1912. Illus. Andrews, loc. cit. pl. 608; Kerr, loc. cit. pl. 211; Du. Breuil, in Risso & Poiteau, Hist. Nat. Orang. ed. 2. 49, pl. 29 bis. 1871-1872.
Type.—Wanting. Substitute type: Philippines, Luzon (Merrill, Species Blancoanae, No. 402).
Distribution.—Philippines, southeastern Asia; widely cultivated in all subtropical regions.
Common name.—Mandarin orange.
A small spiny tree with slender twigs;
leaves broadly or narrowly lanceolate; flowers arising singly or in
small clusters in the axils of the leaves; fruits depressed globose or
subglobose, with thin, loose peel easily separating from the segments,
bright orange or scarlet-orange when fully ripe; seeds small, pointed at
one end, embryo green. (See Hodgson's description of the
cultivated varieties of the mandarin orange in this work.)
In discussing the Chinese species of Citrus in Plantae Wilsonianae (Swingle, 1914a, pp. 141-49), Swingle showed that the true mandarin orange with its thin, loose peel is very different from Citrus nobilis,
which Loureiro described as having a "thick, succulent, sweet, edible
and irregularly tuberculate rind." As Swingle wrote at that
time, "this description is impossible to reconcile with the ordinary
mandarin oranges." It does describe the Cochin-Chinese
orange that is called King (or King of Siam) in the United
States. This latter shows many other important differences
from the typical mandarin orange—differences so great as to force the
authors to the conclusion that it is a hybrid between a mandarin orange
and some other citrus fruit, possibly a sweet orange or a pummelo, or
even a pummelo X sweet orange hybrid. H. Brenier
(1917, p. 214), in commenting on the confusion in the names of
Indo-Chinese citrus fruits, stated (in translation): "It may well be
that hybridization has occurred. It is indeed very probable
that the hybrid King of Siam (C. Aurantium X nobilis [i.e., C. sinensis X C. reticulata]), an orange with high-colored pulp mentioned in the Flore générale de l'Indo-Chine, is not the only hybrid that has originated in our peninsula."
In 1931, Matlack reported that the
chromoplasts in the peel of the King orange are very different from
those of the mandarin orange and similar to those of the sweet orange.25
Another discovery, made by Nelson (1934), is of a fully methylated
flavonol in the peel of the tangerine orange. Nelson stated:
"It seems to be the first instance of a fully methylated flavonol
occurring in nature." It is doubtless analogous to
hesperitin (derived from hesperidin of the sweet orange), naringenin
(derived from naringin of the grapefruit and the pummelo), and
ponciritin (found in flowers of Poncirus trifoliata by Hattori, 1936).
It thus became necessary to find another
botanical name for the mandarin orange. The oldest valid
published name for the mandarin type of orange is Citrus reticulata,
so named for the irregular network of soft, white fibers found between
the loose peel and the juice-filled segments. This name was
published by Blanco in his Flora de Filipinas in
1837. Because his type specimens have disappeared, it was
not entirely clear what plant Blanco had in mind until Merrill (1918)
published his study of Blanco's plants and issued sets of herbarium
specimens including substitute types for Blanco's new
species. Merrill's studies and substitute types show clearly
that Blanco's C. reticulata is, in fact, a mandarin orange. The Blanco species name antedates by three years C. deliciosa Tenore, which was based on the so-called Willowleaf mandarin. The Philippine C. reticulata is
fortunately not an extreme and highly specialized form of this species,
and hence is excellently fitted to be the type of this widespread and
variable species of Citrus. Probably a dozen or more
so-called species have been published for forms of mandarin oranges and
their hybrids and numerous varieties.
6a. Citrus reticulata var. austera Swing. Jour. Wash. Acad. Sci. 32:25. 1942.
Type.—China, Kwangtung Province, Ch'ao-chou (Groff, No. 233, 1918). Herb. Lingnan Univ., Canton, China.
Distribution.—China: Swatow region, Kwangtung Province.
Common name.—Sour mandarin.
Differs from the sweet mandarin orange in
having smaller fruits with intensely acid pulp. The type of
this variety is the sour mandarin called sün kat in Cantonese,
propagated from seed in the Swatow region of Kwangtung, where it is
commonly used as a rootstock for grafting. G. W. Groff in
1918, in a manuscript report covering his work on citrus done in China
under Swingle's supervision for the former Bureau of Plant Industry of
the U.S. Department of Agriculture, described the sün kat as follows:
"Fruits slightly depressed-globose,
2.9-3.3 cm long, 3.3-3.6 cm diam., with smooth, loose peel about 4 mm
thick, capucine yellow (Ridgway, pl. 3) when ripe; oil glands small,
round, far apart, fragrant; segments 9, easily separated; segment walls
thin, tender, white; core 6-8 mm diam., soft; pulp deep chrome yellow
(Ridgway, pl. 3), composed of small, short, pulp-vesicles, clinging
together but irregularly arranged and easily broken; juice reddish
yellow, very sour; seeds about 9, rounded at one end, pointed at the
other, showing white parallel lines from base to tip; leaves
lanceolate-elliptical, blades 6.8 X 2.5 cm, rather acutely cuneate at
the base and narrowed to a blunt apex, with about 10 pairs of lateral
veins; petioles nearly wingless."
This variety is widely grown about
Swatow, China, where it is used as a rootstock upon which to graft the
Ponkan or mi-tong-kan ("honey pot orange") and other famous varieties widely exported from Swatow.
Probably some of the other sour mandarins called kat by the Cantonese are forms of this variety. Some of the so-called kat varieties with large fruits, which as they ripen may become sweet enough to eat, are probably hybrids between variety austera and the sweet mandarin, C. reticulata, or the sweet orange, C. sinensis.
The so-called Rangpur lime (see chap. 4 this work) may upon further study prove to be a form of C. reticulata var. austera
or a dilute back-crossed hybrid of it. It is probable that
the sour mandarin has hybridized with several other species of Citrus in China; hybridized with C. ichangensis, it doubtless gave rise to the widely cultivated Yuzu,
a sort of cold-resistant lemon-substitute widely cultivated in Japan
and northern China; hybridized with a kumquat (some species of Fortunella), it gave rise to the well-known Calamondin, widely cultivated in China and the Philippines and well known in citrus variety collections in the United States.
HYBRIDS OF CITRUS RETICULATA
The following types of hybrids between mandarin oranges and other citrus fruit trees are known:
Tangelos [Citrus reticulata X C. paradisi].
These hybrids, which look very much like
oranges and are often beautifully colored and of delicious flavor, were
first made by Swingle, using safeguarded cross-pollination
technique. They were described and illustrated by Webber and
Swingle (1905, pp. 235-37, pls. 17-19); by Webber (1907, pp. 336-37,
pl. 21); by Swingle 1913e, pp. 87-89, pls. on pp. 94, 95); and by
Hume (1926, pp. 106-08). Additional tangelos that had
proved worthy of being named as horticultural varieties were described
and illustrated by Swingle, Robinson, and Savage (1931, pp. 1-13, pls.
1-7); by Traub and Robinson (1937, pp. 766-67, figs. 6, 7); and by
Hodgson in this work (chap. 4 text, and fig. 4-64).
Similar hybrids have originated in China,
Indo-China, Japan, and other Far Eastern countries by insect
cross-pollination of mandarin oranges and pummelos growing in dooryard
groves of mixed varieties of citrus fruit trees. The
Natsumikan or Natsudaidai of Japan is almost certainly such an
accidental hybrid; it cannot be named as a new species of Citrus
unless similar new species names are coined for the many strikingly
diverse tangelo hybrids that have been made in the United States and
with accurate knowledge of their parentage. The name, Citrus natsudaidai
Hayata, given by Hayata (1911-21, vol. 8, p. 29, fig. 19), cannot be
accepted as a proper one for a chance hybrid known only in cultivation.
Tangors [Citrus reticulata X C. sinensis].
These hybrids have been made by
safeguarded cross-pollination; among them is a promising tangelo-like
fruit named the Umatilla (see Swingle, Robinson, and Savage, 1931, pp.
11-12, pl. 8). The King orange of Indo-China, long grown in
the United States, is doubtless a tangor (see Brenier, 1917, p. 214;
quoted above). The Temple
orange of Florida is probably another tangor (see Traub and Robinson,
1937, p. 775). There are without doubt many tangors besides
the King that are masquerading as oranges in China, Japan, and other
eastern Asiatic countries, where they have originated as chance
hybrids. As there are many more varieties of mandarin
oranges commonly grown in the Far East than in the United States, it is
to be expected that even more variation will be found in Oriental
tangors.
The King tangor was made the type of a
new species which Loureiro (1790, vol. 1, p. 266) published as Citrus nobilis. As
Loureiro's herbarium specimens have almost all been lost, this species
was misunderstood by taxonomists, who considered it to be a true
mandarin orange, i.e., what is now called C. reticulata. It is therefore necessary to abandon the name C. nobilis (see discussion above).
Citrandarins [Citrus reticulata X Poncirus trifoliata].
These trifoliolate hybrids are discussed under Poncirus.
Calamondin [Citrus reticulata var. austera ? X Fortunella sp.].
See under Fortunella.
Yuzu [Citrus reticulata var. austera ? X C. ichangensis].
See under Citrus ichangensis.
Faustrimedin [(Citrus reticulata 'Calamondin' X Fortunella sp.) X Microcitrus australasica].
See under Fortunella.
7. Citrus grandis (L.) Osbeck, Dagbok Ofwer Ostin. Resa 98. 1757. Citrusaurantium [var.] grandis L. Sp. Pl. 2:783. 1753; C. aurantium [var.] decumana L. Sp. Pl. ed. 2. 1101. 1763; C. decumana L. 1767; Aurantium decumana Mill. 1768; Citrus pamplemos Risso, 1826; C. maxima (Burm.) Merr. 1917. Illus. Loisleur-Deslongchamps, Nouv. Duhamel 7:38, 42. 1818; Risso & Poiteau, Hist. Nat. Orang. pls. 62, 63. 1818-1822; Poiteau, Pomol. Franc. 2:pl. 344. 1846; Nooten, Fleurs, Fruits, Feuill. Java 1:pl. 3. 1863; Tanaka, Kankitsu No Kenkyû (Citrus Studies), pl. 3 (col.). 1933; Tillson & Bamford, Amer. Jour. Bot. 25:786, figs. 37-38. 1938; and many other plates (see Stapf, Index Londinensis 2:223 [1930]).
Type.—China, Canton (Osbeck), in Herb. Mus. Stockholm (fide Tanaka).
Distribution.—Southeastern Asia, East Indian Archipelago; widely cultivated in all subtropical regions.
Common name.—Pummelo.
A large, spiny, round-topped tree with
angular twigs, often pubescent; leaves large or very large, oval or
elliptic-oval, with a blunt point at the tip and a broadly rounded base,
often subcordate and even slightly overlapping the winged petiole;
midrib and large veins often pubescent; petioles broadly winged, and
more or less cordate, usually pubescent; flowers very large, borne
singly or in axillary clusters or in subterminal inflorescences; sepals
and petals 5; stamens 20-25, with large linear anthers; ovary globose,
sharply delimited from the deciduous style, with many segments; fruit
large or very large, subglobose, oblate-spheroid or subpyriform; seeds
large, thick, wrinkled. (See Hodgson's descriptions on
horticultural varieties of the pummelo in this work.)
Citrus grandis is one of the most distinct and most easily recognized species of Citrus. It is separated from the other species of the genus by a number of easily seen characters.
Its thick, often pubescent, angular young
twigs, with huge leaves borne on broadly winged, more or less
heart-shaped petioles, its very large flowers and giant pale yellow
fruits often the size of a child's head, make the species impossible to
mistake. The fruit usually has a thick peel and the
pulp-vesicles are much larger than those of other species of Citrus.
Instead of cohering with one another, they easily fall
apart. The membranes that enclose the segments, although
thin, are so strong that they can be peeled off the enclosed mass of
pulp-vesicles easily. If this is done carefully, the segment
remains intact in spite of having lost its covering membrane.
Besides the morphological differences distinguishing it from the other species of Citrus,
the pummelo was discovered to have an important chemical difference
(later found to be shared by the grapefruit): it contains naringin, a
bitter glucoside related to the nearly tasteless hesperidin of the sweet
orange and to the bitter aurantamarin of the sour orange, but differing
from both. (Full information on naringin is given by Will,
1885 and 1887; see also Zoller, 1918, Poore, 1934; and table 3-4.)
Certain Oriental pummelos have a slightly higher content of vitamin C
than oranges or grapefruit. Pummelos are highly esteemed in
both China and Thailand.
8. Citrus paradisi Macf. Hook. Bot. Misc. 1:304. 1830; also Fl. Jamaica 1:131. 1837. Citrus decumana var. racemosa Roem. Syn. Hesper. 1:67. 1846; C. decumana var. patoniana Riccob. Boll. Ort. Bot. Palermo 7:211. 1908; C. maxima var. uvacarpa, Merr. & Lee, Amer. Jour. Bot. 11:383. 1924. Illus. Swingle, in Bailey, Stand. Cycl. Hort. 3:1392, pl. 50 and fig. 1744. 1915; Tanaka, Kankitsu No Kenkyû (Citrus Studies), pl. 4 (col.). 1933; and many others.
Type.—Wanting (fide Tanaka, 1932e, p. 432).
Distribution.—West Indies; now cultivated in all subtropical regions.
Common name.—Grapefruit.
A large, round-topped tree with dense
foliage; twigs angular when young, glabrous or nearly so; leaves larger
than those of the sweet orange, smaller than those of the pummelo,
ovate, bluntly tipped and broadly rounded at the base, glabrous or
nearly so; petioles rather broadly winged but not so broad as those of
the pummelo, oblanceolate to obovate in shape, the somewhat broadly
rounded tip touching the very broadly rounded base of the leaf blade;
flowers large, borne singly or in small clusters in the axils of the
leaves; calyx 5-lobed; petals smaller than those of the pummelo, often
larger than those of the sweet orange; fruits larger than those of the
sweet orange but smaller than those of most pummelos; seeds smaller than
those of the pummelo, white, not yellowish, not ridged as are those of
the pummelo. (See Hodgson's description of grapefruit
varieties in this work.)
The grapefruit apparently originated in
the West Indies. In spite of careful search, it has not been
found native in the Old World, where the parent species is largely
grown and where many horticultural varieties are known.
Another alternative is that the
grapefruit may be a hybrid of the pummelo with the sweet
orange. The morphological characters of the twigs, leaves,
flowers, fruits, and seeds would suggest this. The most
important argument against such an origin of the grapefruit is the
absence of any breakup of self-pollinated grapefruit seedlings into
orange-like and pummelo-like forms. The fairly high
fertility of the grapefruit when pollinated by Citrus reticulata
'Dancy' makes the absence of reversions in the self-pollinated seedlings
of the grapefruit hard to explain. On the other hand, the
hybrids of C. reticulata 'Dancy' with grapefruit show great
variability; some of them are grapefruit-like and others somewhat
orange-like. In view of this fact it seems best to retain
the grapefruit, for the present at least, as an independent but
satellite species immediately following C. grandis, with which it is so closely allied that many Citrus
taxonomists consider it a variety of that species. Patrick
Browne (1756, 1789) was perhaps the first to discuss the grapefruit,
under the name "Forbidden Fruit" or "Smaller Shaddock."
Lunan (1814, pp. 171-73) was the first to use the term
grapefruit. He wrote: "There is a variety known by the name
of Grapefruit, on account of its resemblance in flavor to the
grape." Tanaka (1926b) gave the taxonomic history of
the grapefruit (in Japanese) and in the English summary a good technical
description of its botanical characters.
The fruit of the grapefruit contains a bitter glucoside, naringin,26 first discovered
in the pummelo. According to Zoller (1918, p. 371),
naringin is found in large quantities in the peel of the grapefruit
(from 0.66 to 0.80 grams per 100 grams of fruit). It occurs
without any hesperidin but seems able to give rise to a form of vitamin
P, according to Szent-Györgyi (1938). It is different from
the glycosides of hesperidin, found in the sweet orange, and
aurantamarin, in the sour orange.
It must be admitted that the true nature
of the grapefruit is still unknown. It is to be hoped that
the mystery of its origin can be settled by some of the newer methods
now used in taxonomic research.
HYBRIDS OF CITRUS PARADISI
Tangelos [Citrus paradisi X C. reticulata].
These orange-like fruits, some of them beautiful in color and of delicious flavor, are discussed under Citrus reticulata.
9. Citrus indica Tan. Studia Citrol. 2:164. 1928. Illus. Tanaka, Kankitsu No Kenkyû (Citrus Studies), 94, fig. 80. 1933.
Type.—British India, Khasia, Churra, altitude 2,000-4,000 feet (Hooker f. and Thomson, 15/8/50). Herb. Kew.
Distribution.—Eastern Himalayan
region: "a really wild Citrus found in Nowgong District, Khasi Hills and
Manipur in Assam" (Tanaka, 1937, p. 235).
Common name.—Indian wild orange.
The original description, translated into
English, reads as follows: "Branches terete, spiny, glabrous; leaves
oblong or lanceolate, thick, sub-entire, attenuate at the apex, acute at
the base, veins curved, minute, indistinctly reticulate; petioles
articulated, linear, sulcate; flowers not seen; fruits small, broadly
obovoid or sub-pyriform, solitary on terminal twigs, pedicels very
short; calyx 'hypocrateriform,' lobes triangular, acute; cortex thin,
segments few (?), pulp vesicular, vesicles fusiform; seeds large,
suborbicular, smooth, mono-embryonic." In his discussion
Tanaka stated that this species "has leaves resembling those of C. sinensis, but [the] small, fig-shaped fruit containing extremely large seeds is entirely different from any [other] Citrus."
In the Japanese account of C. indica,
Tanaka gave measurements of various organs and the details not treated
in his Latin diagnosis. His detailed description in Japanese
(1928a, pp. 160-62), as translated by S. Katsura, reads: "Twigs
round in cross-section, rather stout, somewhat zigzag
('wild-goose-procession form'), surface light green, glabrous, not
wrinkled; thorns strong, arising at a broad angle, sharp-pointed; leaves
oblong or lanceolate, pointed at both ends, apex somewhat caudate, the
extreme point sharp or slightly emarginate, the upper side green with
indistinct veins, the underside light-colored with fine curved veins,
without convex oil glands, margin subentire; petioles short, with narrow
wings articulated [with the leaf blade]; leaves near the top of the
branches measure 12.2 X 4.1 cm, petioles 0.8 X 0.2 cm; flowers
indistinct [only calyx seen]; fruits terminal, borne singly on the ends
of branchlets, pedicels extremely short and strong, articulated with the
calyx; calyx funnel-shaped, sepals triangular, acute, thick, glabrous;
young fruits depressed at apex, slightly attenuate at the base, short,
pyriform, about 2 cm diam., peel very thin [red, fide Tanaka, 1937], segments few; pulp-vesicles spindle-shaped, stalked, very delicate; pulp very slimy [fide Tanaka, 1937]; seeds very few, very large, almost round [in outline], flattened, monoembryonic, 11 X 9 X 3.5 mm."
In discussing specimens collected at
Khasia by Hooker and Thomson in August, 1850, and preserved in Kew Herb.
(Tan. Ident. No. 1851), Herb. Bot. Mus., Berlin-Dahlem (Tan. Ident. No.
D-1282), and Rijks Herb., Leiden (Tan. Ident. No. R-1016), Tanaka
stated that they "have branches with numerous spines and luxuriant
growth of leaves. The calyx persists after the flower has
fallen. Flowers borne single in the axils of the leaves,
with extremely short pedicels. Calyx tubular (fistulose ?)
articulated with the pedicels. Ovaries vase-shaped and
scarred where the style has fallen off, resembling ovaries of Lavanga [=Luvunga].
Disk noticeable, below the ovary." In his remarks in
Japanese, Tanaka stated: "The most outstanding point [of this new
species] is the morphological aspect of the flower parts.
The Leiden specimen has sepals pointing [out] like claws with oil cells
on the upper side resembling those of Chalcas [=Murraya], the flowers are evidently borne singly.
"It resembles Metacitrus [Citrus junos, C. ichangensis, and the loose-skinned oranges, C. reticulata and its cultivated varieties and hybrids] in its short pedicels, the thin skin of the fruits and the large seeds like C. yuzu and C. ichangensis but in its depressed shape it resembles Pleiospermium [one of the Primitive Citrus Fruit Trees].
"In the shape of the articulation of the
calyx and pedicels, it resembles Citron and also in the round branches
in cross section, but its leaves are very different because they have no
dentations at all. The leaves show analogies to those of
the sweet orange ? ('amodaidai') group in shape, but are longer and have
far more indistinct fine, parallel and curved veins. The
form of the large leaves borne scattered on strong shoots resembles that
of leaves of the genus Paramignya, in short it is still undetermined to which group this species belongs."
In a later publication, however, Tanaka (1937) stated: "It is really a wild Citrus found in Nowgong District, Khasi Hills and Manipur in Assam. It belongs correctly to Metacitrus, as was predicted by the author, having small sized fruit with thin reddish rind and very slimy pulp, much similar to that of Citrus depressa Hayata. Perhaps of value as a rootstock."
This remarkable species has several
unusual characters which indicate that it may be a truly indigenous wild
species. There is always the chance, however, that C. indica is in fact a hybrid of the remarkable, truly wild Citrus species of northeastern India, C. latipes, which probably has very large seeds like its close relative, C. ichangensis, of central and southwestern China. If so, hybrids between Indian C. latipes with some species of the subgenus Citrus could be expected to have very large seeds like the Ichang lemon, which very probably is a hybrid of C. ichangensis and C. grandis.
10. Citrus tachibana (Mak.) Tan. Bul. Sci. Fak. Terk. Kjushu Univ. 2:52. 1926. Citrus aurantium var. tachibana Mak. Jour. Jap. Hort. Soc. No. 75:2, pl. 1896; C. nobilis var. spontanea Tokutaro Ito, Jour. Coll. Sci. Univ. Tokyo 12:361. 1900; C. aurantium subsp. nobilis var. tachibana Mak. Bot. Mag. Tokyo 15:167. 1901. Illus. Makino, loc. cit. 1896; fig. 3-46 this work.
Type.—Lost. Paratype: Japan, Tosa (T. Makino). Herb. Hokkaido Imp. Univ. (Tanaka ldent. label Sa-2).
Distribution.—Southern Japan: Yamaguchi and Kochi prefectures, south to Kagoshima Prefecture; Ryukyu Islands; Taiwan.
Common name.—Tachibana orange.
A description of this species by T.
Makino, as translated by S. Katsura, reads: "Tree stands over 10
feet. Branches and leaves grow thickly. Strongly
resistant to frost or snow. Fruit somewhat flattened, 2-3
cm lateral diam. Skin smooth, oil glands scattered beneath
the skin. Segment cases 6-7; juice bitter and almost
inedible. Seeds 1-2 in a segment, and rather large in
size. Fruits at first green but turning yellow in the late
autumn. The flavor of the skin resembles that of Yuzu.
Flowers the same as other Citrus plants in time of blooming, shape and
color. In the rainy season of summer the petals begin to
turn white. Needle-like thorns are found on the
branches. Petioles not winged."
A description of the paratype in the
herbarium of Hokkaido Imperial University made by Tanaka reads as
follows: "Branches small and slender; thorns about 3 mm long,
acute. Leaves long, ovate-elliptical, subcoriaceous, broadly
acuminate, obtuse and incised at the tip, somewhat broad and convex at
the base, indistinctly dentate at the margin, midrib slender, straight
and distinct beneath, veins almost indistinct, oil glands indistinct;
petiole short, small, with linear wings which seem to be on the verge of
degeneration. Flowers axillary, solitary,
small. Pedicels 2 mm long, slender, glabrous; scales at the
base triangular, ciliate at the margin. Calyx 3 mm in
diameter; sepals somewhat recurved outward, densely ciliate at the
margin. Disk large, ring-form, subcarnose, depressed at the
apex. Ovary almost globular, attenuate at the base, about 2 X
2 mm in size."
Tanaka (1922, pp. 246-48) published in
English a very interesting account of the tachibana orange, about which
cluster many of the oldest Japanese traditions, showing that the
Japanese people have known this fruit since the very beginning of their
history. As this species is not edible, it would doubtless
not have attracted so much reverent attention had it not been the only
citrus fruit known to the early Japanese.
The widespread occurrence of the
tachibana, from southern Taiwan to the southwestern province of the main
island of Japan, makes it very probable that it is in fact a wild
species that has persisted since prehistoric times. Tanaka
(1931a) published in Japanese a detailed account of the occurrence of C. tachibana
in a wild condition in southern Japan, on the Ryukyu Islands, and also
of its discovery in southern Taiwan where it grows at much higher
altitudes than in Japan but where the temperatures are much the same as
at sea level along the northern limits of its range.
This species is very similar in many of its characters to the mandarin orange, C. reticulata. The
great antiquity of the tachibana in Japan seems to preclude its being a
hybrid or "chance seedling" of recent origin. It probably
should be considered as a satellite species of C. reticulata and somewhat closely related to it.
POSSIBLE HYBRIDS OF CITRUS TACHIBANA
Shekwasha (also spelled Sheequasha, Shiikuwasha, Sekwasa, or even Seequassia).
This plant was described by Hayata (1919,
p. 16) as follows (in translation): "Twigs very green,
applanate-triangular, obtusely bent at the node, sometimes with spines
1-1.5 cm long in the axils of the leaves. Leaves
ovate-oblong, 8-9 cm long, 3.5-4 cm wide, slightly acuminate or broadly
obtuse and retuse at the apex, broadly and obtusely triangular at the
base, margins subentire, slightly crenulate; petioles 8 mm long, very
narrowly winged. Fruits terminal, with very short peduncles,
depressed-globose, 23 mm long, 4.5 cm wide, rounded in outline or
sometimes slightly lobed, deeply sunken at the apex and slightly sunken
at the base, with 7-9 locules, pericarp very thin, 1 mm thick,
luteo-flavescent, rather smooth, flesh acid. Seeds 1 cm
long, 6 mm wide, apex acute, rostrate tip obtuse; embryo pale greenish."
Tanaka (1927c, p. 31) added a few
points in his short description: "Bushy tree about 4 m high.
Leaves small, broad-elliptic, obtuse, petiole short, almost
wingless. Fruit small, oblate, ends concave, very smooth,
oil cells fine, reddish orange. Rind thin,
turgid. Segments many. Center
hollow. Pulp deep-colored, sweetish and rich in pectin,
vesicles finely netted. Seeds very plump, finely striated,
teguman [sic] at chalaza rosy, polyembryo green." He figured the Shekwasha (1933b and 1926c, pp. 190-93, figs. 1, 2) in comparison with Citrus tachibana,
from which it differs strikingly in having larger oil glands distinctly
sunken in the peel, also fewer locules that separate from each other
and from the peel in the ripe fruit. Also Tanaka (1927b, p. 199) contrasted the Shekwasha with the Koji orange of Japan (which he called "Citrus leiocarpa
Hort. nov."), from which it differs in never occurring north of Sanbok
(in the Ryukyu Islands), and "by having pointed leaves, reddish rind,
finely round-netted pectiniferous pulp-vesicles, large seeds of brownish
coat and dark brown chalaza part of tegumen."
The Shekwasha is found, according to Tanaka (1927c,
p. 31), in a wild or semiwild state in the Ryukyu (Luchu) Archipelago
south of Sanbok and in Taiwan. Swingle brought back to the
United States in 1927 a plant of the Shekwasha given him by the Tanaka
Citrus Experiment Station at Tanushimaru, Kyushu, Japan, to which was
assigned the Foreign Seed Introduction number 71180 and C.P.B. number
936. In this country the fruits of this variety when fully
ripe are bright orange-colored and the less mature fruits are
orange-buff or capucine yellow; the pulp is near primuline yellow
(Ridgway, 1912, pl. 16). The seeds are pointed-obovoid and
somewhat compressed, 11 to 13 by 7 to 8 by 5.5 to 6 mm, with a very
finely striate but nevertheless remarkably smooth and even testa for a Citrus; the chalazal cap is reddish-brown (Ridgeway, pl. 27); the embryo is pale greenish. Tanaka reported (1926c, p. 192) that the pulp of the Shekwasha contains much pectin.
The Shekwasha grows so vigorously in the
peculiar sandy-loam and porous-limestone soils of extreme southeastern
Florida that it should be tested there as a rootstock. The
fruits are poor-flavored.
Hayata (1919, p. 16) named the Shekwasha as a valid species of Citrus (C. depressa); in the same paper, however, he named as "new species" of Citrus
several other forms that, according to his own statement, are probably
hybrids. The Shekwasha has just the characters that would
result from the hybridizing of the native C. tachibana of Taiwan and the Ryukyu Islands with some form of the mandarin orange (C. reticulata) introduced from the Chinese mainland.
Subgenus Papeda
Common name.—Papedas.
Pulp-vesicles with very numerous droplets
of acrid oil; petioles always large and broadly winged; flowers small,
usually less than 2 cm diam.; stamens free, or, if cohering in bundles,
then flowers larger (1.5-3 cm diam.) and petioles very long, 1 3/4-3
times longer than broad.
This subgenus comprises a number of truly wild species of Citrus,
many of them still to be found growing in primeval forests of the
Monsoon region. There are two sections in the subgenus Papeda, the section Papeda, comprising the typical species, and the section Papedocitrus, which is intermediate in character between the subgenus Citrus and the section Papeda, having flowers much like those of the subgenus Citrus and leaves like those of the section Papeda. The fruits are almost never eaten, but the acrid juice of the fruits of the species belonging to the section Papeda is widely used by primitive peoples, especially Malays, Melanesians, and Polynesians, as a hair wash.
As noted above in the discussion of the subgenus Citrus, the species of Citrus belonging to the subgenus Papeda
have been shown by Tillson (1938, pp. 21, 30; also Tillson and Bamford,
1938, pp. 788, 790) to possess a decidedly simpler type of vascular
anatomy of the flowers than do the species of the subgenus Citrus. In this important character the subgenus Papeda agrees with the other five genera (other than Citrus)
included in the True Citrus Fruit Tree group. This fact
will doubtless prove important in studying the course of evolution of
the commonly cultivated species of Citrus, all of which belong to the subgenus Citrus.
This makes it very desirable to learn much more than we now know
regarding the species of papedas in their relationship to the subgenus Citrus, on the one hand, and to the genera Clymenia, Microcitrus, Eremocitrus, Poncirus, and Fortunella,
on the other. Tillson's discovery of a primitive character
in the papedas serves to emphasize how very different they are from the
true oranges of the subgenus Citrus.
The species which belong to the section Papeda
have small flowers, 1.2 to 1.7 (rarely 2) cm in diameter, with free
stamens not cohering in groups. The pulp-vesicles of all the
species contain numerous globules of very acrid oil and are sometimes
attached to the radial locule walls for one-half to three-fourths the
distance from the dorsal wall to the center of the fruit.
To facilitate an understanding of the subgenus Papeda, the detailed key
was prepared to give a perspective view, as it were, of the taxonomic
characters of the species that could not easily be obtained from
independent descriptions, no matter how detailed they might be.
Subgenus Papeda Section Papedocitrus
Flowers large (1.5-3 cm broad when open);
stamens at first coherent nearly to the tips, but separating later into
a few bundles, connate only at the base; winged petioles
long-elliptical with more or less parallel sides; seeds crowded, often
very short, very thick, and angular.
The section Papedocitrus comprises
two species growing in southwestern China, northeastern India, and
northern Burma, far to the north of the range of the species that
constitute the section Papeda. Section Papedocitrus is intermediate in its flower characters between the section Papeda and the subgenus Citrus,
but the pulp-vesicles contain numerous droplets of acrid oil and the
winged petioles often equal the area of the leaf blade, just as in the
section Papeda.
The fruits of the species of this section
do not seem to be used by primitive peoples for washing the hair, but
it is believed by some that in China the fruits of C. ichangensis were
anciently, and perhaps still are, used in medicines.
Striking hybrids have arisen in China between this species and species
of the subgenus Citrus. One of these hybrids, the
Ichang lemon, is cultivated on a small scale by the Chinese.
The Yuzu, which shows many points of similarity with C. ichangensis,
is doubtless another of these hybrids; it has been known in China since
ancient times and is widely grown both in northern China and in Japan.
11. Citrus ichangensis Swing. Jour. Agr. Res. 1:4 (excluding fruit). 1913. Illus. Swingle, loc. cit. pl. 1, figs. 1, 4-7 (excluding figs. 2, 3 of fruit); fig. 3-47 this work.
Type.—China, Hupeh Province, Hsing shan district (E. H. Wilson). Herb. Arnold Arbor., Harv. Univ., Cambridge.
Distribution.—West-central and southwestern China: Hupeh, Szechwan, Kweichow, and Yunnan provinces.
Common name.—Ichang papeda.
A spiny shrub or small tree usually 5-15
ft. [1.5-4.6 m] high; twigs angular when young, with stout, sharp
spines, 1.5-2.5 cm long, often reduced or lacking on flowering twigs;
leaves narrow, 4-6 times longer than wide, mostly 8-11.5 X 1.8-3 cm;
petioles very large, broadly winged, obovate or oblong-spatulate, evenly
rounded at the tip and narrowed abruptly at the base, usually 3.5-6 X
2-3 cm; leaf blade ovate-acuminate, often more or less caudate,
emarginate at the tip and evenly rounded or bluntly pointed at the base,
usually 3-6 X 1.8-3 cm, often not equaling the winged petiole in area;
flowers 2.5-3 cm diam., 5-merous; sepals thick, 3 mm long and 3 mm wide,
with minutely ciliate margins; petals oblong, 1.5-2 X 0.5-0.8 cm,
white; stamens 20, at first all connate to the tips, finally breaking up
into several bundles, about 10 mm long; pistil about 10 mm long; style
very short, caducous; stigma nearly as large as the ovary; ovary with
7-9 locules, ovules numerous in each locule; fruits small, glabrous, 3-4
cm diam. in dried specimens (probably 3.5-5 cm when fresh), peel rough,
2-4 mm thick in dried specimens; seeds large, very thick, 12-18 X 12-18
X 7-9 mm in dried material, very blunt at both ends, with a chalazal
cap about 12 X 5 mm, apparently monoembryonic.
This species differs from its congeners
in having large, very thick seeds and slender leaves 4-6 times longer
than broad, with very large, winged petioles often as large or larger
than the blade. It differs from C. hystrix in having oblong, rather than triangular, winged petioles and much larger flowers with connate stamens. (See fig. 3-47.)
This remarkable plant,27
which grows in a truly wild state in central and southwestern China, is
doubtless the most cold-resistant of all the evergreen species in the
orange subfamily. It differs greatly from the other species
in the subgenus Papeda in having large flowers, partly connate
stamens, and large, very thick seeds, which are nevertheless
monoembryonic. The leaves also differ from those of all
other species of Papeda in having extremely long but rather
narrow winged petioles, often exceeding in area the slender, pointed,
lanceolate leaf blades.
In 1926, Swingle brought to this country a
healthy young seedling of this plant from Hupeh Province, grown for him
at Nanking, China, by C. C. Hu. As C. ichangensis is the hardiest known evergreen species of Citrus, it is of great interest for use in breeding cold-resistant hybrids, such as the Ichang lemon and Yuzu.
HYBRIDS OF CITRUS ICHANGENSIS
Ichandarins [Citrus ichangensis X C. reticulata cv. satsuma group].
An ichandarin was produced by the citrus
experts of the former Bureau of Plant Industry (now encompassed by the
Agricultural Research Service) by applying the pollen of the Ichang
papeda to properly prepared flowers of the satsuma orange.
Naturally all chances of foreign pollen reaching the crossed flowers
were excluded, and of course the stamens of the satsuma flowers had been
cut away before any pollen had matured.
The leaf blades of this hybrid are
broadly elliptical, 6 to 8.5 by 2 to 4 cm, slightly acuminate at the tip
and cuneate at the base (angle 70° to 85°), margins minutely serrulate,
dentate above the middle. The leaf blades differ only
slightly from those of the Yuzu, a hybrid in which the leaf blades are
more acuminate at the tip and more broadly rounded at the
base. The winged petioles are obovate, oblanceolate, or
elliptical, broadly rounded at the tip and gradually narrowed into the
base when the petiole is merely margined. The petioles are
so much like those of the Yuzu that it is often impossible to
distinguish between them with certainty. This hybrid is of
interest chiefly in that it throws light on the origin of the Yuzu, a
well-known Chinese and Japanese citrus fruit tree.
It is very probable that if some strain of C. reticulata other
than the satsuma, for example the tangerine or the Willowleaf mandarin,
had been used as one of the parents the leaf blade would have been more
acuminate at the tip and more broadly rounded at the base, i.e., like
the leaf blade of the Yuzu, which is doubtless such a hybrid.
Yuzu [Citrus ichangensis X C. reticulata var. austere ?].
Illus. Takahashi, Kankitsu Saibai 112, fig. 31. 1912; Makino, Shokubutsu Dzukan 1064, fig. 2022. 1917; Tanaka, Jour. Hered. 13:pl. facing p. 243. 1922; Hu, Nogyo Oyobi Engei 5:1637-1638, figs. 34-37. 1930; idem, Calif. Citrog. 16:544, pl. 2, fig. 15. 1931; idem, Jour. Agr. Ass. China Nos. 126-127:58, fig. 15. 1934; Murakoshi, Nai-gai Shokubutsu Genshoku Dai-zukan 5:118, pl. 24, fig. 251 (col.). 1935.
The Yuzu is a medium-sized spiny tree;
leaves lanceolate-acuminate, with rounded bases but with pointed,
usually acuminate tips, slightly crenulate-margined toward the tips,
leaf blades 5-7 X 2.5 X 3.5 cm; winged petioles obovate, 18-30 X 6-15
mm, with entire or very faintly crenulate margins; fruits
depressed-globose, usually with 10 locules, 5-7 cm diam., 4.5-5.5 cm
high, with a rough, bumpy peel, greenish in color when ripe; pulp very
acid, and somewhat bitterish; seeds plump, about 12-14 X 7-8 X 6-7 mm.
This well-known citrus fruit tree of
China and Japan is doubtless another ichandarin resulting from an
accidental cross-pollination of some cultivated variety of the mandarin
orange by the Ichang papeda, probably accomplished by some
insect. The Yuzu is unlike either parent species in many
important taxonomic characters; however, there has been little
opportunity to learn its characters or experiment with it since one
parent, C. ichangensis, is a wild species (apparently never
cultivated in China) that was not discovered until 1913. The
hybrid nature of the Yuzu was not known even in the Orient, where C. ichangensis is a botanical curiosity. As has been described above,
hybrids that show astonishing similarity to the Yuzu have now been
produced in this country between the Ichang papeda and the satsuma
orange (a form of C. reticulata).
The Yuzu is sparingly cultivated in
north-central China, in Kiangsu, Chekiang, Hupeh, and Kansu provinces,
and in the plateau regions of southwestern China and as far south as
Yunnan Province. It is more commonly grown in Japan, both
for its acid fruits, which are used as a substitute for lemons or limes,
and as a rootstock for the satsuma and other cultivated varieties of
citrus fruits.
Meyer, in October, 1914, found this hardy
citrus fruit tree in northwestern China, in the latitude of Atlanta,
Georgia, at Hsi-Chi village, near Siku (Lat. 33° 44' N., Long. 104° 30'
E.), in the southern part of Kansu Province. It was growing
at an altitude of 610 to 1,372 meters (2,000 to 4,500 ft.) along with
walnuts, persimmons, pomegranates, and the Trachycarpus
palm. Meyer (1918) described the fruit as follows: "The
fruits were loose-skinned, round flattened, the size of mandarin
oranges, color of rind light yellow; rind full of oil glands, smelling
like a fine lemon; segments separating easily; fairly juicy and of an
agreeable sharp sour taste; contains plenty of large seeds."
Meyer's photograph, taken at His-Chi, Kansu Province, was published by
Tanaka (1922, pl. facing p. 243).
Two strains of this hybrid grown in
north-central China were described by Hu (1934, pp. 47-48).
They are: (1) hsiang ch'êng (aromatic ch'êng), a name current in Chekiang and Kiangsu provinces; and (2) Lo han ch'êng (Buddhist
disciple Ch'êng), a name used in T'ang-ch'i, Chekiang
Province. Hu (1930) has shown the first in his figures 34
and 35 and the second in figures 36 and 37.
Tanaka has directed attention (1933b) to certain Chinese records which seem to prove that this plant was known and cultivated in ancient China under the name yu. This name is still used for it in Japan but not in China, where the name is now applied to the pummelo (C. grandis), a very different species having much larger fruits with agreeably flavored sweet pulp. The Yuzu is now called ch'êng tzu in China and was so called as early as 1108 A.D. by Tang Shên-wei in his great illustrated herbal, the Chêng lei pên ts'ao, published in that year.
In the "Spring and Summer Annals" of Lü Pu-wei, who died in 237 B.C., the yu
of that epoch was described as follows (as translated by Michael J.
Hagerty): "Some are sweet and some are sour. The sour are
called hu kan or Barbarian sweet. At present the common people sometimes speak of the ch'êng as yu
but this is wrong." This last sentence proves, as noted by
Hagerty, that there were already in the third century B.C. two different
fruits called yu. It seems probable that the Japanese name yuzu, which corresponds to yu tzu
in the Chinese spoken language, has been kept with its ancient meaning
in Japan, but that the meaning has for many centuries been lost in
China.
The Yuzu was named Citrus junos (as
a good species) by Tanaka, but, as has been shown above, it is very
probably a hybrid of the Ichang papeda and some Chinese cultivated
variety of the mandarin orange and therefore cannot be recognized as a
good botanical species.
The Yuzu is worthy of trial as an acid
fruit for the home garden in subtropical or warm-temperate climates that
are too cold to permit the growth of other acid citrus
fruits. The Yuzu was formerly used widely in Japan as a
rootstock for the satsuma orange, but now the trifoliate orange is
almost exclusively used in nurseries which propagate the satsuma on a
large scale, doubtless partly because seeds of the Yuzu are only to be
obtained in moderate quantity from fruits that have a market value,
whereas trifoliate orange seeds can be had in large quantity from fruits
that are of no value.
Nagai and Takahashi (1928, pp. 2018-22,
and 1925 [in Japanese]) found that of the five following
rootstocks—Yuzu, sweet orange, sour orange, trifoliate orange, and
Japanese summer orange (Natsudaidai)—the Yuzu gave the best results when
approach-grafted in order to rejuvenate Thomson navel trees on
trifoliate orange rootstocks. The sweet orange did nearly as
well, but it is subject to foot rot, a disease that does not attack the
Yuzu.
Shangyuan, or Ichang lemon [Citrus ichangensis X C. grandis var. ?].
Illus. Swingle, Jour. Agr. Res. 1:figs. 2-3. 1913; Hu, Calif. Citrog. 16:544, fig. 18. 1931; idem, Jour. Agr. Ass. China Nos. 126-127:61, fig. 29. 1934.
Distribution.—China: Lower valley of Yangtze River in Hupeh, Anhwei, Kiangsu, and Chekiang provinces; sparingly cultivated.
An erect, much branched tree with lower
branches short, giving the tree a columnar outline; twigs glabrous,
spiny; leaves ovate, ovate-lanceolate, or ovate-acuminate, apices
sometimes minutely emarginate, sometimes bluntly pointed, margins
obscurely crenulate, leaf blades about 3 times as long as the petioles,
6-9 X 2.5-3.5 cm, glabrous, tips rounded, margins subentire; petioles
more or less broadly winged, 20-25 X 6-12 mm; fruits large, 8-11 X 7-10
cm, broadly obovate, usually with a low mammillate tip surrounded by a
shallow furrow; peel thick, 7-10 mm, lemon yellow when ripe, very
fragrant; oil glands concave; segments 10 or 11 with numerous large
seeds, 4-6 per segment, usually 16-20 (sometime longer) X 9-12 X 7-10
mm, tapering into a flattened truncate base, sometimes polyembryonic;
pulp very acid, but with a strong, aromatic aftertaste; pulp-vesicles
fusiform, 8-10 X 2-4 mm, on stalks 2-8 mm long, with a central streak of
minute granules of acrid oil.
The Shangyuan, or "Ichang lemon," which
was introduced into the United States about 1914, has proved to be very
resistant to winter cold. In southern Alabama it has endured
without harm temperatures that injured or killed most of the satsuma
orange trees of the same age growing near by, although the satsuma is a
very cold-resistant variety. At first the plant was supposed
to be C. ichangensis but was soon found to be very different, as
it has very much larger fruits and very much smaller winged petioles;
it is, in fact, a hybrid. There is some variation among
different trees of the Ichang lemon growing in China, such as is found
among other violent hybrids of Citrus.
Hu in 1930 named this hybrid Citrus grandis var. Shanyuan; the next year he corrected the spelling of the varietal name to read Shangyuan
(1931, p. 544). He noted the similarity of this tree to the
pummelo but stated that the fruits are smaller and have a bitter
taste. He considered it to be a hybrid of the
pummelo. He also reported (1930) that it is grown in the
lower valley of the Yangtze River, in Anhwei, Kiangsu, and Chekiang
provinces; later (1931) he stated that the fruit, though ornamental, is
not eaten and that the tree is hardy enough to be grown in Nanking.
Hu's varietal name for this hybrid is a phonetic rendering of the Chinese name for it, namely, Hsiang yüan, or "Fragrant ball," an allusion to its pleasing aroma. Tanaka (1930a, p. 32) changed Hu's name to a botanical one, Citrus hsiangyuan Hort. Later he named the hybrid Citrus wilsonii (1932b, p. 37), but stated: "The present species unquestionably has Citrus junos in one parent and seems to be a cultigen originated through the chance seedling."
There is no valid reason for calling this
plant a botanical species, as it is undoubtedly a chance hybrid that
arose under cultivation. Its resemblances to the Yuzu,
remarked by Tanaka, are doubtless due to the fact that both the Yuzu and
the Ichang lemon, or Shangyuan, are hybrids of C. ichangensis with two different species of the subgenus Citrus. Fortunately, the International Code of Botanical Nomenclature (Lanjouw,
1961, p. 31) now gives a very simple method of citing such sports and
cultigens under the name of the species from which they arose by giving
the variety name in some living language (not in Latin) following the
species name and surrounded by single quotes. Under this
rule any cultivated form of a species of Citrus can be cited after the species name under its common name; for example, C. sinensis 'Hamlin' or C. reticulata 'Dancy.' Many of the complex hybrids of Citrus can best be handled in this way until their origin is worked out experimentally.
In China, the ripe fruits of the Ichang
lemon are used to perfume rooms or cabinets. In the United
States, the fruit has been occasionally used to make lemon pie, the heat
of baking evidently driving off the acrid oil that gives a disagreeably
strong odor to "lemonade" made from the juice; some who have made pies
from Shangyuan juice prefer them to regular lemon pies.
The Ichang lemon is a very hardy plant
and deserves trial as a rootstock in this country, where it grows
vigorously. It produces very numerous large seeds that
should make it easy to grow in the nursery. It also produces
pollen freely and hybridizes spontaneously with the satsuma orange if
growing near by; doubtless it could be crossbred with other forms of
citrus fruits as well. It should be used in breeding new
hybrids for trial as rootstocks or as acid fruits for home use in the
cotton belt.
12. Citrus latipes (Swing.) Tan. Studia Citrol. 2:155. 1928. Citrus ichangensis subsp. latipes Swing. Jour. Agr. Res. 1:12. 1913. Illus. Tanaka, Kankitsu No Kenkyû (Citrus Studies), 79, fig. 72, also 167, fig. 136(1). 1933; fig. 3-48 this work.
Type.—Northeastern British India, Khasi Hills, Living Bridge (Hooker f. and Thomson). Herb. Kew.
Distribution.—Northeastern India:
Khasi Hills; northern Burma; grows in the mountains at considerable
elevation, 500-1,830 m [1,640-6,000 ft.].
Common name.—Khasi papeda.
A thorny tree similar to C. ichangensis
but having leaf blades more variable in size and shape and with the
tips subacute or even bluntly rounded, not apiculate or subcaudate with
blunt points as in C. ichangensis. The flowers, instead of being borne singly in the axils of the leaves as in C. ichangensis,
are sometimes, at least, borne in small axillary racemes with 5-7
flowers. These latter flowers are much smaller, are 4-merous
(instead of 5-merous as is the large single flower of C. ichangensis), and all the parts are smaller. However, the fruits are borne singly and resemble those of C. ichangensis except
for having a thicker peel, of which the inner layer is chalky white
just below the outer green layer. The seeds are also smaller
and more numerous than those of C. ichangensis and are arranged 5-7 in each segment.
The following is a detailed description of flowers and fruits (after Tanaka, 1928a,
p. 155): Inflorescences racemose, having 5-7 flowers; peduncles short,
5-8 mm, pubescent; pedicels 7-8 mm long, moderately thick, becoming
thicker at the upper end where they join the calyx, striated, glabrous;
flower buds medium-sized, ovoid, about 7 X 9 mm, rounded at the apex,
showing oil glands indistinctly at the surface; calyx discoid, 4 mm
diam., lobes 4, broad, semicircular, wrinkled, slightly convex at the
tip and curving outward, rather thick, slightly pubescent at margins,
glabrous above; flowers, when open, 1.5 cm diam.; petals 4, spreading
horizontally, thick, oval; stamens 18-20, 7-8 mm long and about 1 mm
wide, filaments almost free at the tip but arranged in 6-7 groups each
composed of 3-4 united together at the bases, thick, flat, wrinkled,
pointed at the tip; anthers oval or elliptic-oval, about 1.5 mm long,
pointed, with small gland at the apex; pistils shorter than stamens,
about 7 mm long; ovaries depressed-globular, 2 mm diam.; styles rather
stout, 2.5 mm long, 1 mm diam., distinctly articulated with the ovary;
stigmas large, depressed-globose, 1.5-2.5 mm diam., with 4 sometimes
indistinct furrows; fruits medium-sized, almost globular, slightly
compressed at both ends; oil cells moderately small, more or less equal
in size, rather dense, convex; peel somewhat thick, composed of rather
dense tissue; central column (axis) of even width, moderately large;
segments 9, fairly large, outer margin very much rounded, inner margin
also rounded; pulp-vesicles few, fairly large, spindle-shaped, not
short, relatively well developed with a thick membrane, stalks very
short; seeds numerous, arranged 5-7 in each row, rounded, moderately
large, parallel and horizontal.
This species was founded on plants
collected in the Khasi Hills of northeastern India, but very similar
forms are found in the mountains of northern Burma. The type
specimen in the Kew Herbarium on which Swingle based C. latipes (1913c, p. 12) has a fruit in cross section measuring 5 cm in diameter, peel 5 to 6 mm thick, with nine segments.
In view of the extreme cold-resistance of the typical C. ichangensis (and its hybrid, the so-called Ichang lemon) it would be well worth while to introduce C. latipes into
the United States and see if it also is hardy and perhaps of value for
use in breeding new hardy acid citrus fruits and hardy rootstocks.
Subgenus Papeda Section Papeda
Subgenus Papeda Section Eupapeda Swing. in Webber & Batchelor, Citrus Indus. 1:432. 1943.
Flowers small (less than 2 cm, often less
than 1.5 cm diam.); stamens free from the beginning; winged petioles
broad, and more or less triangular; seeds small or medium-sized, not
angular, much longer than broad.
The species of the section Papeda of the subgenus Papeda
are remarkable in having very large winged petioles and small flowers
(often very small) with free staminal filaments. The
pulp-vesicles contain numerous droplets of acrid, bitter oil that gives
the pulp a very disagreeable taste. The pulp-vesicles are
often attached not only to the dorsal walls of the locules, but also to
the radial walls for one-half to three-fourths the distance from the
dorsal wall to the central core of the fruit. In this
character these species approach Clymenia.
As a result of the widespread use of the
fruits by natives, these species have come into culture on a small scale
about villages throughout the East Indies and in Melanesia and
Polynesia. In this way these species have been exposed to
cross-pollination not only with other species of the Papeda group but also with edible-fruited species of the subgenus Citrus grown as dooryard trees.
Rumphius, near the close of the seventeenth century, described and figured many forms of the Papeda
group found growing in Amboina and in other islands of the East Indian
Archipelago; his observations were published by Jan Burmann in 1741-1755
(Herbarium Amboinense, vols. 2 and 5). Wester (1913; 1915, 1917a, 1917b, and 1924) published good descriptions and photographic illustrations of many forms of the section Papeda
group found growing wild or cultivated on a small scale in the
Philippine Islands, especially in the southern islands, Bohol, Cebu,
Negros, and Mindanao. Several forms are likewise found in
the southern half of Luzon, the northernmost island.
It is clear from the works of Rumphius and Wester that the species of the section Papeda have been very extensively hybridized, almost as much so as those of the subgenus Citrus.
However, many of the species of the section Papeda
group still occur in a truly wild state in the primeval forests of
southeastern Asia, the East Indies, New Guinea, and neighboring
islands. In these species and varieties it is thus possible
to see the unobscured results of many million years of evolution,
whereas in the edible-fruited species, varieties, and forms belonging to
the subgenus Citrus the results must be surmised rather than
directly observed. The papedas, because of their acrid,
disagreeable flavor, have not been considered by citrus experts of
sufficient value to merit study. However, hybrids between
the species of the subgenus Papeda and species of the subgenus Citrus
have been known to yield rootstocks very well adapted to support the
commonly cultivated citrus fruit trees. Several of the wild
species of papedas are very vigorous and deserve trial as rootstocks for
the edible species of citrus. Nothing is known about the
vitamin C content of the papedas or about which glucosides, if any, they
contain.
13. Citrus micrantha Wester, Phil. Agr. Rev. 8:20, pls. 5c, 6b. 1915. Citrus macroptera var. micrantha (Wester) Tan. Trans. Nat. Hist. Soc. Formosa 22:430. 1932. Illus. Wester, loc. cit. pls. 5c, 6b, and Phil. Bur. Agr. Bul. 27:pl. 12. 1913.
Type.—Philippines, Bohol (Wester, No. 4829). Herb. Bur. Sci., Manila.
Distribution.—South Philippines.
Common name.—Small-flowered papeda. Native name: Biasong.
The original description of this species by
Wester reads as follows: "A tree attaining a height of 7.5 to 9 meters,
with comparatively small but sharp spines; leaves 9 to 12 centimeters
long, 27 to 40 millimeters broad, broadly elliptical to ovate, crenate,
rather thin; base rounded or broadly acute; apex acutely blunt pointed;
petioles 35 to 60 millimeters long, broadly winged, up to 40 millimeters
wide; wing area sometimes exceeding leaf area; flowers small, 12 to 13
millimeters in diameter, white, with a trace of purple on the outside, 2
to 5, in axillary or terminal cymes; petals 4; stamens free, equal, 15
to 17; ovary obovoid, locules 6 to 8; style slender; distinct; fruit 5
to 7 centimeters long, 3 to 4 centimeters in transverse diameter,
averaging 26 grams in weight, obovate to oblong-obovate, somewhat
compressed towards base; apex blunt pointed; surface fairly smooth or
with transverse corrugations, lemon yellow; skin comparatively thick;
pulp rather juicy, grayish, acid; aroma similar to that of samuyao;
juice cells short and blunt to long, slender and pointed, sometimes
containing a minute greenish nucleus; seeds many, flat, pointed, more or
less reticulate."
This species stands out from all others of the subgenus Papeda
because of its very small 4-merous flowers, only 1.2-1.3 cm diam. when
open. The fruits are oval or obovate, blunt-pointed at both
ends, 5-7 cm long but only 3-4 cm wide, with very few locules (only
6-8). The leaves have broadly ovate blades, blunt-pointed at
both ends, 3.5-6 cm long, 2.7-4 cm wide. The broadly winged
petioles, measuring 3.5-6 X 3.5-4 cm, have a nearly straight or
slightly curved top and gradually curved sides, tapering to a blunt
base. Seeds many, flat (2.5-3 mm thick).
This species is sparingly cultivated in
the southern Philippine Islands (Cebu, Bohol, Negros, and Mindanao),
where it is called biasong. Wester stated that the
fruit of this species is used as a hair wash but is not eaten and is of
no economic importance.
13a. Citrus micrantha var. microcarpa Wester, Phil. Agr. Rev. 8:21, pl. 7b. 1915. Illus. Wester, loc. cit. pl. 7b, and Phil. Bur. Agr. Bul. 27:pl. 14. 1913.
Distribution.—Southern Philippines: Cebu and Bohol.
Common name.—Small-fruited papeda. Native name: Samuyao.
The original description of this variety
by Wester reads as follows: "A shrubby tree, 4.5 meters tall, with
slender branches and small, weak spines; leaves 55 to 80 millimeters
long, 20 to 25 millimeters broad, ovate to ovate-oblong or elliptical,
crenulate, thin, of distinct fragrance, base rounded to broadly acute;
apex obtuse, sometimes notched, petioles 20 to 30 millimeters long,
broadly winged, about 14 millimeters wide, wing area somewhat less than
one-half of the leaf blade; flowers in compact axillary or terminal
cymes, 2 to 7, small, 5 to 9 millimeters in diameter, white, with trace
of purple on the outside; calyx small, not cupped, petals 3 to 5;
stamens 15 to 18, free, equal; ovary very small, globose to obovate;
locules 7 to 9, style distinct; stigma small, knob like; fruit 15 to 20
millimeters in diameter, roundish in outline; base sometimes nippled;
apex an irregular, wrinkly cavity; surface corrugate, greenish lemon
yellow; oil cells usually sunken; skin very thin; pulp fairly juicy,
acid, bitter with distinct aroma; juice cells very minute, blunt,
containing a small greenish nucleus; seeds small, flattened, sometimes
beaked."
The samuyao was found by West and
Brown (1920, pp. 208-09) to yield from the rind "a clear, almost
colorless oil which is very fragrant. It should be useful as
a perfumery oil." The peel yielded 1.29 per cent of
oil. They stated that the crushed fruits are used by the
women of Cebu for cleansing the hair and are added to coconut oil to
give it fragrance when applied to the hair. The tree bears
within five years from planting and produces fruits during the entire
year, but more abundantly during the rainy season. West and
Brown (1920, fig. 70) show the fruits as distinctly pyriform, broadly
rounded at the tip and tapering into a narrow, conical base.
This variety has the smallest fruit and
the smallest flowers of any True Citrus Fruit Tree known but curiously
enough has more segments in the fruit (seven to nine) than C. micrantha
(six to eight), although the fruits of the latter are much larger, 5 to
7 by 3 to 4 cm, instead of 1.5 to 2 cm, as in the variety microcarpa.
Wester stated (1915, p. 22) that in Bohol Island, P.I., "a somewhat more vigorous variety of the samuyao was found that is called samuyao-sa-amoo" which has "fruits a little larger, and smoother, and longer than broad, otherwise similar to the samuyao." This description calls to mind Rumphius' Limonellus aurarius,
the goldsmith's lime, which occurs sparingly in Amboina, Moluccas, and
Ternate, a few hundred miles directly south of Bohol.
According to Rumphius (1741, vol. 2, p. 109, pl. 30), the fruits of this
plant are the smallest of all the limes (his figure shows ovoid fruits
2.5 to 3 by 2 to 2.5 cm) and the leaves are also small, only 3 inches
long in all, about one-third of which represents the cordate, winged
petiole. The fruits are not eaten but are used by goldsmiths
to clean gold objects. The fruits also enter into native
medicines.
Both C. micrantha and its variety microcarpa are of much scientific interest, as they are perhaps the most primitive members of the subgenus Papeda, itself the most primitive group of species of the genus Citrus.
14. Citrus celebica Koord. Fl. N. O. Celebes, Mededeel. uit 's Lands Plantent. 19:639, also 370. 1898. Illus. Koorders, Suppl. Fl. N. O. Celebes 2:pl. 19. July, 1922; loc. cit. 3:pls. 10-11. December, 1922.
Type.—Northeastern Celebes (Koorders). Hort. Bot. Buitenzorg, Java (now Kebun Raya, Bogar, Java).
Distribution.—Northeastern Celebes, southern Philippines.
Common name.—Celebes papeda.
Leaves with small, lanceolate, subcrenulate blades, 4.5-5.5 X 2.5-3.5 cm; winged petioles larger than the blades,
5-6.5 cm long, 3-3.4 cm wide, oblanceolate, with a subcordate or
slightly curved upper end and gradually rounded sides tapering into a
deltoid base, having from 5-10 mm of the petiole almost wingless;
margins faintly crenulate; flowers occurring in 3- to many-flowered
spikes or small cymoid clusters in the axils of the leaves; flowers
medium-sized, 15-17 mm when open, 4-5-merous; ovary reversed-pyriform,
tapering sharply below, broadly rounded at the tip with many (17-20)
locules; style short, 5-6 mm; stamens short, free; fruits large (10 cm
diam.), globose, with a very thick peel (about 3 cm); seeds small,
probably monoembryonic.
A small tree 5 m high, growing in a wild
state in primeval forests at Karowa, in extreme northeastern Celebes
(Minahasa) (Lat. 1° 15' N., Long. 124° 45' E.); fruits inedible.
The original description of this species
published in 1898 was not adequate to show its nature clearly, as the
description did not give the number of locules in the ovary, an
important character in the subgenus Papeda. Twenty-four years later C. celebica was fully figured; then it became clear that this species was distinct from C. macroptera.
14a. Citrus celebica var. southwickii (Wester) Swing. Jour. Wash. Acad. Sci. 28:533. 1938. Citrus southwickii Wester, Phil. Agr. Rev. 8:16-17, pls. 3c, 4c. 1915. Illus. Wester, loc. cit. pls. 3c, 4c, and Phil. Bur. Agr. Bul. 27:pl. 16b. 1913. (fide Wester, loc. cit. 1915 = C. southwickii).
Type.—Philippines, Bohol (Southwick, Wester). Herb. Bur. Sci., Manila.
Distribution.—Philippines: Bohol and Mindanao.
This plant appears to be a variety of Citrus celebica,
with which it agrees in having very numerous locules (15-19) in the
ovary. It also agrees well in flower characters, especially
in the short style and the ovary tapered toward the base, but differs in
having smaller fruits with thin peel, and in having the blade of the
leaves decidedly larger than the winged petioles and often much
blunter-pointed. The winged petioles are similar to those of
C. celebica but decidedly smaller. Both the species
and the variety have smooth fruits. The difference in the
diameters of the fruits is misleading, since the fruits of variety southwickii, because of their thin skin, have more pulp than the decidedly larger but very thick-skinned fruits of the species.
The variety southwickii was found
by E. F. Southwick in Bohol, where it is not uncommon and where it is
cultivated. It was also found by Wester in Baganga (Lat. 7°
35' N., Long. 126° 35' E.), in eastern Mindanao, about 450 miles
north-northeast of Karoa in northern Celebes. It has been
introduced into the United States.
It is possible that this plant may prove, upon more detailed study, to be a complex hybrid of C. celebica with
one or two other species. The thin, smooth skin and the
abundant, though acrid, pulp and the short, broad-winged petioles arouse
suspicion that it may be a complex hybrid of C. celebica with a pummelo (C. grandis), or with some other species of the subgenus Citrus.
This variety is promising for breeding
purposes because of its fair-sized, juicy, smooth, thin-skinned
fruits. The bitter taste of the pulp, due to the acrid oil
in the pulp-vesicles, can doubtless be removed by hybridization with the
species of the subgenus Citrus that have little or even no oil in the pulp-vesicles, such as C. reticulata. It is highly probable, even if variety southwickii proves to be a dilute hybrid of the pummelo, that wild forms of C. celebica will
be found native in the southern islands of the Philippines, since
southern Mindanao is only about 300 miles north of northeastern Celebes;
Bohol, where variety southwickii occurs, is less than 400 miles distant.
OTHER POSSIBLE HYBRIDS OF CITRUS CELEBICA
Alemow.
This hybrid, named C. macrophylla by Wester (1915, p. 16, pls. 3b, 6c),
is sometimes cultivated in Cebu, P.I. It has large leaves,
with the blades 12 to 14 cm long and 6 to 8 cm wide, with much smaller,
subtriangular, short-winged petioles, measuring up to 3.5 cm wide near
the top. The fruits are very large, 8.5 to 10 cm in
diameter, subglobose to oblong, more or less narrowed at the base, with a
rough, transversely-corrugated, but rather thin skin. The
fruit has 13 to 16 segments and rather dry, sour pulp, considered
inedible even by the natives.
This seems to be a hybrid of C. celebica, or some other species of the subgenus Papeda, with a species of the subgenus Citrus, probably a pummelo (C. grandis). It has shown some promise as a rootstock for lemons in California.
Kabuyao.
This is another possible hybrid of C. celebica. It is called kabuyao in Luzon Island, P.I., and kopahan in Bohol Island. It was described by Wester (1915, pp. 17-19, pl. 5b, fig. 1; and 1924, p. 93, pl. 31c) as typical C. hystrix. It
differs from that species, however, in having more numerous stamens (30
to 36) and more locules (13 to 18) in the ovary. The fruit
is subglobose or short-pyriform, 7 to 9 cm long and 7 cm in diameter,
with a smooth skin; the pulp-vesicles contain a "nucleus," doubtless
composed of droplets of acrid oil such as are found in all species of
the Papeda group and in most of their hybrids.
Amongpong.
This plant is found in Bohol Island, P.I., and is evidently similar to the kabuyao, but according to Wester (1915, p. 18) it has only 26 to 30 stamens and a larger fruit, 10 cm in diameter.
These two hybrids, the kabuyao and the amongpong, and other similar fruits may perhaps be hybrids of C. celebica (which has many locules in the ovary) with C. macroptera or with C. hystrix, both members of the subgenus Papeda. The increased number of stamens and the larger fruits might result from such hybridization.
15. Citrus macroptera Montr. Mém. Acad. Sci. Lyon 10:187. 1860. Citrus papuana F. M. Bail. Contr. Fl. Brit. N. Guin. 1903; C. aurantium subsp. saponacea Safford, Contr. U.S. Natl. Herb. 9:226. 1905. Illus. Bailey, loc. cit. (text fig.); Tanaka, Kankitsu No Kenkyû (Citrus Studies), 131, fig. 106. 1933 (?); fig. 3-49 this work.
Type.—New Caledonia, Art Island (Montrouzier). Herb. Fac. Med. Pharm., Univ. Lyon, France.
Distribution.—Thailand, Indo-China, Philippines, New Guinea, New Caledonia, and Polynesia (possibly escaped from culture here).
Common name.—Melanesian papeda.
Father Montrouzier's original description
in Latin may be translated as follows: "Petioles broadly winged,
distinctly articulated; leaves elongate-acuminate, only twice as long as
the petiole, subcrenulate, with very numerous [oil] glandlets, 5-6
inches [12-14 cm] long excluding the petiole; twigs subcompressed, with
one long spine on young twigs and one short spine on old twigs in the
axils of the leaves; peduncles axillary, often extra-axillary, several
crowded together, bracteate; calyx with 4-5 small sepals; corolla with
4-5 petals with valvate aestivation; petals elongate, concave; stamens
20; ovary subhemispherical; style thick, round; stigma depressed; fruit
with 10-12 segments, pubescent; segments 1-2 seeded, with scanty pulp,
depressed, almost without juice, about the size and form of an
orange. A tree 15-16 feet [4.2-5 m] high, growing near the
houses of the natives on the Island of Art. It flowers in
September, and is commonly called don gan."
Bailey's original description of his Citrus papuana, doubtless a synonym of C. macroptera,
reads as follows: "Branchlets green, very angular like those of the
common orange, all parts more or less covered with amber-coloured
lenticular glands; axillary spines straight, erectopatent, about 1/2 in.
long. Leaves broadly-lanceolate, 2 to 5 in. long, the
winged petiole cuneate 2 to 3 1/2 in. long and from 1 to 2 in. broad at
the top; margins with broad shallow crenulations, the lenticular glands
very numerous on the midrib, both surfaces punctate; lamina very freely
disarticulating from the petiole. (No flowers
collected.) Fruit globose, about 2 1/2 in. in diameter, pale
yellow, smooth; glands small, slightly concave; ring about 1/2 in.
thick; cells 10. In foliage this species somewhat resembles C. hystrix, D.C."
This species was discovered by Father
Montrouzier on the Island of Art, situated a few miles to the northwest
of the north end of New Caledonia. What appears to be the
same species was described and figured in 1903 by F. M. Bailey from
Milne Bay, New Guinea, about 1,200 miles to the northwest.
Unfortunately Bailey had no flowers and Montrouzier in his account does
not describe the flowers in adequate detail.
This species is characterized by large
leaves, sometimes 10 or 12 inches long (including the very large winged
petiole) and 2 inches wide; it has subglobose fruits the size and shape
of an orange, but with very little juice.
Wichmann (1917, p. 202) told of getting a
fresh supply of fruits at a village on the shores of Lake Sentani in
northern Dutch New Guinea (now West Irian, Indonesia). Among
these were thick-skinned fruits of a Citrus with pulp "so
disgustingly bitter that it was hours before one's mouth got free from
the taste." This persistent bitter taste is due to the
numerous droplets of acrid oil that are found in the pulp-vesicles of
all species of the subgenus Papeda and in some of the hybrids of them with species of the subgenus Citrus.
A beautiful Citrus which Swingle
saw growing wild in the primeval forest on the lower slopes of Mount
Maquiling in southern Luzon, P.I., belongs, he believed, to C. macroptera. It
has usually long-pointed leaves with very large, entire, winged
petioles, and smooth, subglobose fruits the size of a large
orange. The conviction that this Citrus is truly
indigenous in the primeval forests on the lowers slopes of Mount
Maquiling is substantiated by the observation of D. A. Herbert (1924, p.
195), who reported that this Citrus (which he called C. hystrix)
occurs occasionally in the dipterocarp forest, which was the original
forest growth on Mount Maquiling up to an altitude of about 600 meters.
This species doubtless grows wild in New
Guinea, Bismarck Archipelago, Celebes, southern Luzon, and the southern
islands of the Philippines. It has reached New Caledonia,
Fiji, Samoa, Guam, and probably many other of the Polynesian islands,
probably being carried by the Polynesians for use in
washing. Safford (l.c., pp. 226-27) gave a firsthand account
of the use of the fruit pulp of this species in Guam not only for
washing the hair, but also as a substitute for soap in washing
clothing. He stated further that the macerated leaves form a
lather when water is added. Safford whose observations
apply also to Samoa, cited F. Reinecke (1898, pp. 642-43) to show that
both the pressed-out fruit juice and the macerated leaves form a lather
when rubbed and that they are specially useful in washing the hair to
free it from the lime which is much used by the natives to bleach the
hair. Both Safford and Reinecke noted that after the fruit
falls off the tree the peel hardens and becomes like a stony shell in
drying.
Of all the species of the Papeda group, C. macroptera is
probably the most promising for use as a rootstock. F. M.
Bailey (1903, p. 1) was so impressed with the vigor of the specimens of
this species from Milne Bay, New Guinea (his C. papuana), that he recommended it as a rootstock for cultivated citrus fruit trees in tropical Queensland. Hybrids of C. macroptera with vigorous species of the subgenus Citrus might be expected to show still greater energy of growth.
The plants of C. macroptera that
have been grown in Florida from seed obtained from trees found growing
wild on Mount Maquiling, Luzon, P.I., were reported by T. Ralph Robinson
(Keys, 1923) as being immune to withertip and resistant to
canker. This large-fruited, disease-resistant, and vigorous
strain is promising for use in breeding new and superior citrus
rootstocks.
HYBRIDS OF CITRUS MACROPTERA
Moli kurikuri hybrid.
A hybrid of C. macroptera, very probably with the pummelo (C. grandis), was named C. vitiensis by Tanaka (1928b,
p. 715). It was found in Fiji in 1860 by Berthold Seemann
(1862), who collected it together with the parent species, C. macroptera,
giving both specimens the same number (58). Both sheets are
preserved in the Kew Herbarium. One of the specimens is the
typical C. macroptera Montr., the moli kurikuri of the
natives, said by Seemann to be a wild orange, found on the island of
Viti Levu, that is not eaten but is "used to kill lice by washing the
hair." The manuscript note on the moli kurikuri was
attached, doubtless by accident, to the sheet on which was mounted the
specimen of the hybrid, which shows the following characters: twigs
terete, internodes short (1.5 to 3.5 cm); spines straight, acute, short
(only 3 to 4 mm on mature branchlets); leaf blades narrow, lanceolate,
acuminate or caudate at apex, broadly rounded at base, 4.5 to 5 by 1.8
to 2.5 cm, margins shallowly serrate, veins numerous but obscure;
petioles winged, obpyramidal, with slightly curved tips curving abruptly
and nearly straight-sided, cuneate bases 20 to 26 by 10 to 15
mm. Seemann's manuscript note reads further: "it was
plentiful on the banks of the Namosi river growing in company of
shedocks28
and flowering together with…[that] species." This
circumstance would easily account for the finding of a hybrid between
these two species! This hybrid has, in fact, leaves somewhat
like those of the so-called Shangyuan, or Ichang lemon, which is doubtless a hybrid of C. ichangensis (also of the subgenus Papeda) and C. grandis.
To name as a valid new species a chance
hybrid found growing in immediate proximity to both of its parents is to
give unmerited importance to such a plant.
Webber's Philippine hybrid.
Webber's Philippine hybrid is a mandarin-like citrus fruit tree which was named C. webberii by Wester (1913, pl. 14; 1915, p. 13; 1917, p. 108; 1924, p. 96, pls. 20b, 30a) in honor of his former chief, H. J. Webber. It is called kalpi
in the Bicolano dialect. According to Wester (1924, p. 96),
it is a medium-sized, handsome tree 5 to 10 meters tall, bearing very
juicy, acid fruits that can be used like lemons. It grows in
both the large islands of the Philippines, Luzon and
Mindanao. The fruit is variable in size, depressed-globose,
with 9 to 11 segments; skin very thin, yellowish when ripe.
Wester (1917, p. 107, pls. 1, 3, 4) reported that the kalpi when used as a rootstock appears more congenial and produces a more rapid growth than other of the Citrus species of Philippines origin. It seems to be a hybrid of the native C. macroptera with the common Philippine mandarin (see the Chinese Yuzu, a similar hybrid of the papeda with a mandarin).
Another form of Webber's Philippine
hybrid is a tree with weeping branches considered by Wester (1917, p.
108, pl. 1a) to be "the most ornamental species in the genus Citrus."
It grows well at the Citrus Research Center at Riverside, California,
where its handsome shape and beautiful foliage make it a perpetual
tribute to Dr. Webber. It should also be tested as a
rootstock, as it produces seeds abundantly.
Kansi.
A Philippine citrus called kansi by the natives of Bohol, where it is sparingly cultivated, may be a hybrid of C. macroptera, which occurs in Bohol, with a pummelo (C. grandis). The kansi
has leaf blades broadly ovate to elliptical, pointed at the tip,
broadly acute at base, with subentire margins, 9 to 12 by 3 to 4.5 cm;
winged petioles broadly obovate, even-margined, 3.5 to 4.5 by 2.5 to 3
cm, having less than half the area of the leaf blade; stamens 20 to 23,
free; ovary oblate; fruit oblate, smooth, lemon yellow, 38 to 40 by 44
to 46 mm, pulp acid, peel 3 to 5 mm thick, segments 11 to 14, seeds
many, flattened, monoembryonic. This was called C. hystrix var. boholensis by
Wester (1915, p. 19, pls. 4, 5), who stated that the fruit is eaten
with fish and also makes a fairly good ade. That it is a
hybrid of C. macroptera with a pummelo is borne out by the
statement of Wester (1915, p. 12) that pummelos with from 11 to 14
segments in the fruits are widely distributed in the Philippines.
15a. Citrus macroptera var. kerrii Swing. Jour. Wash. Acad. Sci. 32:24. 1942. Illus. Swingle, loc. cit. figs. 1 and 2.
Type.—Thailand, Nakawn Sawan,
Kampêngpat, Mê Lamung (Lat. 16° 15' N., Long. 98° 58' E.), altitude
about 500 m (Kerr, No. 6081, coll. June 7, 1922). Herb.
Univ. Aberdeen.
Distribution.—Northern and central Thailand; North Vietnam: Tonkin; southern China: southern Yunnan Province.
Common name.—Kerr's Thailand papeda.
Differs from the species in having larger
fruits, 8-9 cm diam. instead of up to 5-6 cm, with more segments, 12-13
instead of 10 (rarely 12), with smaller, thinner-walled, ovoid
pulp-vesicles attached in large numbers to the side (radial) walls of
the locules for 2/3-3/4 the distance from the dorsal walls of the
segments to the center of the fruit, and with a thicker peel, 12-14 mm
thick instead of 5-6 mm. The spines on vigorous, young,
vertically-growing shoots are very long (6-7 cm), straight, sharp,
arising nearly at right angles to the direction of the twig, but on
fruiting branches they are usually only 5-10 mm long or wanting
altogether. The leaf blades are sometimes ovate, rounded at
both ends, often emarginate at the apex, about 4-7 X 3-3.5 cm, with
merely undulate margins; petioles broadly winged, obovate, with slightly
undulate margins, 5-7 X 3-3.8 cm, often slightly larger than the leaf
blade. In another collection from Ban Kragê, Thailand (Kerr,
No. 11983), the leaf blades are 8-10 X 4-5 cm, broadly ovate-acuminate,
tapering into a narrow acumen, blunt at the very tip; petioles 5.5-7.5 X
3.5-4.5 cm, obovate, with crenulate or subserrate margins.
In material from Tung Kung in northern Tonkin (Groff, No. 19877), the
leaf blades are lanceolate-acuminate, 6-8 X 2-3.5 cm,
crenate-denticulate above the middle, and tapering into a long, slender
acumen which often has a very sharp apex; petioles 5-7.5 X 2.2-4.4 cm,
with entire or slightly undulate margins. Flowers are
lacking on all the material examined except on Kerr's No. 11983, where
they arise singly (or in 2's or 3's) in the axils of the leaves on
short, slender, glabrous pedicels, 3-5 mm long; flower buds subglobose,
3-4 X 2.5-3 mm; calyx very small, saucer-shaped, lobes 4 (?), bluntly
triangular, 1 mm long, 2 mm wide; petals 3.5-4.5 X 3-4 mm; stamens
numerous (16-20 ?) with slender free filaments. Several
specimens show fruits. They are subglobose, 8-9 cm diam.,
with thick peel (1-2 cm) almost entirely composed of white spongy tissue
with a superficial green layer, only about 1 mm thick, which contains
very numerous, nearly spherical oil glands. The fruits show
12 and 13 segments with lateral (radial) walls 2-2.5 mm thick where they
join the peel, tapering to 0.8-1 mm where they join the clearly
delimited cylindrical core. The pulp vesicles are very
numerous, obovoid, very small, 1.5-2 mm long, bluntly pointed, tapering
into slender stalks, 1-3 mm long. The pulp-vesicles are
attached not only to the adaxial wall of the carpel but also to the
lateral (radial) walls 2/3-3/4 the distance from the dorsal wall to the
core. The seeds are immature in Kerr's specimens, but seem
to be placed almost exactly in the inner angle of the segments and to
lie nearly parallel to the core.
The type specimens of this variety were
collected in Nakawn Sawan Province of Thailand by A. F. G. Kerr, who
stated that it is a "common tree in evergreen forest, growing up to 10 m
high, fruit 8 cm diam.; lower shoots armed with long
spines." Another of Kerr's specimens of this same number in
the Aberdeen University herbarium that Swingle had opportunity to
examine through the courtesy of J. R. Matthews shows a piece of a very
angular, upright-growing new shoot having five internodes, with five
very strong, sharp, straight spines, 6 to 7 cm long, 4 to 5 mm in
vertical diameter at the base and 2 to 2.5 mm in transverse
diameter. These spines arise almost exactly at right angles
to the twig. The winged petioles are very nearly the same
length as the spines that arise in their axils. They are 3
to 4 cm wide at the very broadly rounded tips and taper to a cuneate
base.
This variety shows some resemblance to C. latipes,
but apparently has decidedly smaller flowers and more globose fruits
with much thicker peel. More study is needed to allocate
this interesting papeda with certitude to its proper taxonomic position.
What seems to be a form of this variety
with acuminate leaf blades was found by the late G. W. Groff when at
Lingnan University, Canton, China, while making botanical exploration in
cooperation with the former Bureau of Plant Industry, U.S. Department
of Agriculture, in northern French Indo-China in January,
1932. Groff collected good herbarium material (Lingnan
Univ., No. 19877) from four trees (very like those found by Kerr)
growing at Tung Kung in Tonkin (about Lat. 22° 15' N., Long. 102° 50'
E.) 130 kilometers (80 miles) west of Lau Kai (11-12 km northwest of Cha
Pa at Ta Ching on the forest road from Ku Ho to Ta Ching) on the
Yunnan-Tonkin border. The trees were growing in the heart of
the forest at an altitude of about 5,000 feet in rich moist soil.
15b. Citrus macroptera var. annamensis Tan. Bul. Mus. Hist. Nat. Paris, 2 sér. 2:164. 1930.
Type.—French Indo-China, Co-inh Mountains, Nhatrang, Annam (Poilane, No. 4650). Herb. Mus. Hist. Nat., Paris.
Distribution.—Known only from the type locality.
Common name.—Annam papeda.
The original description reads in
translation as follows: "Leaves very large, leaf blades ovate, acute at
apex, obtuse at the base; petioles broadly winged; petiole wings oblong,
truncate, a little longer than the leaf blade. Fruits
medium-sized, ovate-obovoid, peel glabrous, thin; pulp-vesicles scanty,
very short."
A photograph of the type specimen of this
variety sent to Swingle by Tanaka shows the leaf blade to be broadly
oval or lozenge-shaped, 6-7 X 3.5-4 cm, bluntly pointed or subacute at
the apex and broadly cuneate at the base, with the upper half or
two-thirds with undulate, crenulate-dentate margins; petioles broadly
winged, linear-oblong, decidedly longer than the leaf blade but not any
wider, 7-11 X 3.5-4 cm, truncate at the apex and abruptly rounded at the
corners into a more or less oblong section with nearly parallel margins
including 1/2-3/4 the distance to the base; the lower 1/2 or 1/4 of the
petiole is gradually narrowed into a cuneate base, with a very short
segment of the petiole (3-6 mm long) at the base wingless; the fruit is
depressed globose, 4.5 cm high and 5.2 cm wide; peel 3-4 mm thick.
This variety is strikingly different from typical C. macroptera in the oblong shape of its very long winged petioles, which resemble those of some forms of C. ichangensis; the fruits, however, are entirely different from those of this latter species, but are much like those of C. latipes. This variety differs from C. macroptera var. kerrii
in having oblate fruit with rather thin peel instead of globose fruits
with remarkably thick peel, often five times as thick as that in this
variety.
According to Tanaka (1937, p. 238), this
variety occurs also in Thailand, Burma, and northeastern India, where
the fruits are stored and "used for refreshing drinks when other small
acid Citrus fruits are gone." He did not hesitate to
identify it with the Citrus combara of Rafinesque (1838, p. 142),
but the description there given is inadequate and might apply to many
forms of bitter orange belonging to the subgenus Papeda. This and other forms of C. macroptera
should be studied carefully, as some of them may prove to be distinct
species. All of them should be tested as rootstocks for the
cultivated species and varieties of True Citrus Fruit Trees belonging to
the subgenus Citrus.
16. Citrus hystrix ["Citrus histrix"] DC. Cat. Pl. Hort. Bot. Montp. 97. 1813. Citrus hystrix DC. Prodr. 1:539. 1824; Papeda rumphii Hassk. 1842; Citrus papeda Miq. 1855; C. torosa Blanco, 1873. Illus. Rumphius, Herb. Amboin. 2:pls.
26 (fig. 1), 27, 28. 1741; Risso & Poiteau, Hist. Nat. Orang. pl.
59 (col.). 1818-1822; Vidal & Soler, in Blanco, Fl. Filip. ed. 3. 4:38, pl. 408 ("var. colobot"). 1880; Vidal, Sinop. Fam. Gen. Pl. Leñosas Filip., Atl. pl. 25, fig. F. 1883; Bonavia, Cult. Orang. Lem. India Cey. Atl. pl. 225, figs. A-K. 1890; Sawyer, Agr. Jour. India 5:pls. 36 (col.), 37, 38. 1910; Wester, Phil. Bur. Agr. Bul. 27:1, pl. 11. 1913; Ochse, Indische Vruchten, fig. 107. 1927; idem, Fruits Fruitcult. Dutch East Ind. pl. 46 (col.). 1931; Redgrove, Gard. Chron. 3 ser. 89:149, fig. 76. 1931; fig. 3-50 this work.
Type.—Montpellier (De Candolle). Herb. Delessert, Geneva, Switzerland (fide Tanaka, 1931b, p. 11).
Distribution.—East Indian Archipelago, Ceylon, Burma, Malay Peninsula, Philippines; widely naturalized, native habitat uncertain.
Common name.—Mauritius papeda.
J. J. Ochse (1931, pp. 117-18) gave the following description of C. hystrix as
it occurs in the Dutch East Indies (now Indonesia): "Low tree or shrub,
2-12 m high; trunk crooked, asymmetric or angular, rather thin,
branched near the base; crown irregular, densely branched; branchlets
thin, when young compressed-acutangular, when older terete, dark green,
glabrous with scattered glandular dots, armed with axillary spines;
spines short, stiff, subulate, green with hard brown or orange-coloured
tips, obliquely erect, solitary, glabrous, 0.2-1 cm long. Leaves
alternate or biseriate, stalked unifoliate, orbicular-ovate or
ovate-oblong, lanceolate; base cuneate, obtuse or rounded, rarely
subcordate, apex obtuse, rounded or obtusely acuminate, often notched;
patently serrate-crenate, coriaceous, glabrous on both surfaces, above
dark green, shining, beneath light green or yellowish-green, dull,
densely pellucid dotted, fragrant when bruised, 3-15 cm long, 2.5-6 cm
wide. Petiole from 0.3-0.5 cm above the base upwards with
large, foliaceous wings; the winged part obovate or obcordate-oblong,
with an acute, cuneote, obtuse or rounded base and an obtuse, truncate,
rounded or slightly emarginate apex, patently crenate-exsculptate,
coriaceous, above dark green, shining, beneath light green or yellowish
green, dull, with scattered pellucid dots, including the wings 1-8 cm
long, 1-4.5 cm wide, sometimes very similar to the leaf itself and not
rarely for a greater or smaller part connate with it. Inflorescences axillary or terminal, dense, 1-5-flowered, glabrous. Flowers
smallish, shortly stalked, 4-5-merous, fragrant, in bud globose, white,
0.5-0.7 cm diam.; pedicel terete, yellowish green, glabrous, 0.1-0.5 cm
long. Calyx cupular, afterwards flat, 4-lobed,
glabrous within and without, 0.2-0.35 cm diam.; lobes broadly
ovate-triangular, acute or shortly acuminate, yellowish white with
violet margins, ciliate, ±0.1 cm long. Petals 4-5,
ovate oblong, with a narrowed base and a narrowed or acuminate, obtuse
apex, yellowish white or tinged with red, glabrous, with scattered
pellucid dots, 0.7-1 cm long, 0.3-0.5 cm broad. Stamens
24-30, quite free, 0.4-0.8 cm long, filaments thickened above the base,
with a filiform apex, glabrous, 0.3-0.6 cm long; anthers
elliptic-oblong, 0.15-0.25 cm long. Ovary depressed globose, glabrous, with a tuberculate-folded surface, 0.2-0.4 cm diam.; style short, robust, terete, glabrous, 0.1-0.15 cm long; stigma depressed globose, glabrous. Fruit
pendulous, globose, ovoid or ellipsoid, with an abruptly contracted
obtuse or rounded base and a rounded or slightly depressed apex, crowned
by a short style-rest, very irregularly bumpy, glabrous, with many
scattered glandular dots, when ripe yellow or yellowish green, feebly
shining, 5-7 cm diam.; peel thick, its exterior layer of ±0.2 cm
thickness, yellowish green, the inner part white; pulp yellowish green,
very sour and slightly bitter, faintly fragrant; fruiting pedicel very
short, 0.3-0.5 cm long. Seeds ovoid-oblong, 1-1.5 cm long, 0.5 cm thick; cotyledons and plumule white."
Ochse stated that "this species, called Djerook pooroot in the Dutch East Indies, is nowhere cultivated on a large scale but…very often on a small one."
This much misunderstood species was named
by De Candolle from young seedlings, not yet in flower, grown from seed
sent to the Montpellier Botanic Garden from Mauritius, where it was
probably not native. De Candolle redescribed it in 1824 but
had not yet seen flowers or fruits.
Thanks to flowering material from
Mauritius and from Montpellier preserved in the Kew Herbarium, it is
possible to determine with certainty that C. hystrix is the species with very bumpy fruits belonging to the subgenus Papeda
that is widely distributed in Indonesia. The fruits usually
have 10 to 12 segments (rarely 13 or 14). The leaves are
blunt-pointed, usually of medium size, 8 to 12 by 3 to 5 cm, more or
less irregular at the tip and sometimes slightly emarginate.
The margins are more or less crenate. The winged petiole,
usually two-thirds to three-fourths as long as the leaf blade, is
broadly rounded and blunt at the base, often subtruncate at the tip,
often with more or less crenate margins.
The flowers are small, with short,
entirely free stamens, as in all the other species in the section Papeda.
The fruits are almost always bumpy or tuberculate. The
pulp-vesicles were first described by Penzig (1887, pp. 131-32), who
stated: "They are provided with a slender very long stalk which suddenly
enlarges toward the free end, forming a small round or oval body
pointed at the tip." Penzig noted that they differ from the
pulp-vesicles of the other species studied by him in showing "a large
amount of oil accumulated in their centers." This
accumulation of numerous droplets of oil, often of a very strong and
acrid flavor, is characteristic of all the species of the subgenus Papeda. The cotyledons are epigeous in germination.
Citrus hystrix, although the best
known and most widely distributed species of this subgenus, is not the
most vigorous species, and not the most promising for use as a
rootstock. It has undoubtedly hybridized with other species
of the subgenus Papeda in the village fruit gardens of the people of the East Indian Archipelago and also with species of the subgenus Citrus.
Doubtless some of these hybrids are included among the bizarre forms
described and figured by Wester (1913 and 1915).
Bonavia reported (1886, p. 215) that the fruit of C. hystrix is
never eaten; however, it is used by the natives in Ceylon as an
insecticide for washing the head and also for smearing on the feet to
kill land leeches. The tree is often cultivated near the
villages for these purposes. According to Bonavia, C. hystrix
may have come into Ceylon with the Dutch and their Malay servants for
use as a hair wash. This use may account for the wide
distribution of the species throughout the East Indian Archipelago and
adjoining parts of the Asiatic mainland.
HYBRIDS OF CITRUS HYSTRIX
Lemon Martin.
The Limo tuberosus or Lemon Martin of Rumphius (1741, vol. 2, pp. 101-03, pl. 26, fig. 1) is probably a hybrid of C. hystrix with the lemon (C. limon).
The leaves are crenate-margined with broad, subcordate winged petioles,
also crenate-margined. The fruit is somewhat lemon-shaped
but exceedingly rough, with bosses or warts 5 to 10 mm in
diameter. The fruit figured by Rumphius is 5.54 by 4.5 cm
and is said to be a yellowish-green when ripe "like a Spanish lemon";
moreover the odor is somewhat like that of the lemon. The
juice is vinous, not very sour; according to Rumphius, the fruits can be
eaten raw, especially if sliced and sprinkled with sugar.
Rumphius stated that the Lemon Martin in his day (in the last quarter of
the seventeenth century) was believed to have been brought to the East
Indies by the Portuguese and to have been grown by Europeans in many
parts of the archipelago.
It seems very probable that the Lemon
Martin of Rumphius arose from lemons brought by the Portuguese from
Europe that were propagated from seed in the East Indies and, through
chance cross-pollination by insects, became hybridized with C. hystrix, or with some other species of the subgenus Papeda.
Subtribe 3. Balsamocitrinae: Hard-Shelled Citroid Fruit Trees
The subtribe Balsamocitrinae, the
Hard-Shelled Citroid Fruit Trees, is a remarkable side shoot of the
orange subfamily not very closely related to any of the other
subtribes. It includes seven genera occupying two
noncontiguous areas of distribution. Four genera occur in
southeastern Asia from India to Burma and Indo-China, reaching some of
the neighboring East Indian islands, and also reaching Luzon, the
northernmost island of the Philippines. The other three
genera occur in tropical Africa, from Uganda west to the Ivory Coast and
south to the Republic of the Congo. None of the
Hard-Shelled Citroid Fruits are native to New Guinea, Australia, or the
Polynesian islands in spite of having spread from southeastern Asia as
far as West Africa. This subtribe is a side branch of the
ancestral tree of the orange subfamily, a side branch that parallels the
subtribe Citrinae, the Citrus Fruit Trees. These two
subtribes resemble each other in having large fruits with hypermerous
ovaries (with 6 to 20 locules) with numerous ovules (6 to 16+) in each
locule. The genera comprising the subtribe Balsamocitrinae
have no pulp-vesicles, but they show a high specialization in the
structure of the fruits, which usually have a hard, almost woody exocarp
(leathery in the genus Swinglea). The locules are
filled with resinous gum and the seeds are sometimes sparingly hairy,
woolly, or covered with laciniate paleae.
The seven genera of this subtribe fall
into three groups. The first, group A (the Tabog Group),
comprises only one genus, Swinglea, native to Luzon, the
northernmost island of the Philippines. This genus has
fruits so dissimilar in structure to those of the genera in the other
two groups that question may be raised concerning its degree of
relationship to them.
Swinglea, unlike the other members
of the subtribe Balsamocitrinae, has oval fruits with a leathery (not
woody) shell which has 8 to 10 longitudinal ribs (somewhat like a
muskmelon) corresponding with the number of locules. The
outer wall of the fruit, which does not separate like the peel of an
orange, contains crowded, radially arranged ellipsoid oil glands, 4 to 7
mm long. The locules contain many hairy seeds immersed in a
glutinous fluid apparently secreted by ellipsoid mucilage glands, 5 to
10 mm long, which slant toward the axis of the fruit and also toward the
radial axis of the locule into which they open, as shown in figure 3-51.
The second set of related genera (four in
all) constitutes group B (the Bael-Fruit Group). The
best-known genus in this group is Aegle, native to India, Ceylon,
Burma, and Indo-China, and widely cultivated in the East Indian
Archipelago, especially Java. The other genera of this
group, Balsamocitrus, Afraegle, and Aeglopsis,
occur thousands of miles to the west, in tropical Africa, from Uganda
west to the Ivory Coast and southward to the Republic of the Congo and
Angola. It seems remarkable that those genera in group B
which have the largest fruits, obviously of common ancestry, were able
to jump over the great distance from southeastern Asia to West Africa,
but failed to reach the Philippine Islands, to say nothing of New Guinea
and Australia.
Aegle and Balsamocitrus (both with trifoliolate leaves), Afraegle (with normally trifoliolate leaves, reduced to unifoliolate or to simple leaves on the older branches of A. gabonensis), and Aeglopsis
(with unifoliolate leaves) are obviously all closely related but differ
in important taxonomic characters, such as the number of locules in the
ovary and the number of stamens. Aegle has 8 to 20 locules in the ovary, Afraegle 6 to 8, Balsamocitrus 8, and Aeglopsis 6 to 8 (sometimes 5). Aegle
has woolly seeds, whereas the other three genera all have glabrous
seeds. The development of the disk also varies greatly in
the four genera: Aegle and Balsamocitrus have a cylindric disk below the ovary and of about the same diameter, whereas Afraegle and Aeglopsis have a greatly enlarged and lobed disk that partly encloses the base of the ovary.
The third set of related genera, group C (the Wood-Apple Group), comprises two genera, Feronia and Feroniella, which occur in India, Burma, Indo-China, and Java. Feronia limonia
is often cultivated for its fruit. This group differs in
very important taxonomic characters from the other two groups, and is
undoubtedly one of great antiquity that now represents a side line of
development in the subtribe Balsamocitrinae.
Feronia and Feroniella,
spiny trees with pinnate leaves and small leaflets, have ovaries in
which the locules (four to six) coalesce at an early stage of
development into a single cavity with numerous ovules borne on the walls
(parietal placentae), a character unique in the whole plant family
Rutaceae.
The evolution of the subtribes
Balsamocitrinae and Citrinae has doubtless proceeded along parallel
lines from a common ancestral form, both subtribes having attained
nearly the same degree of specialization. It is not
possible, however, to exhibit in a linear arrangement of the tribes,
subtribes, and groups of the Rutaceae the true status of the
evolutionary development of the different categories. It
would require a map, diagram, or model in order to show the parallel
development of the subtribes Balsamocitrinae and Citrinae.
Here in the printed text where the subtribes are arranged in the linear
order of the pages and lines of the printed book, the Balsamocitrinae
fall at the end of the series, although in reality the Citrinae are more
highly developed with their extraordinary pulp-vesicles that fill all
the space not occupied by the seeds in the locules of the
fruit. However, to intercalate the subtribe Balsamocitrinae
between the subtribes Triphasiinae and Citrinae would obscure the close
relationship clearly exhibited by some of the genera of the subtribe
Triphasiinae with some of the more primitive genera of the tribe
Citrinae. Keys to the groups and the genera of the subtribe Balsamocitrinae are presented.
GROUP A. THE TABOG GROUP
This group contains only one genus, Swinglea,
the tabog of Luzon, the northernmost island of the Philippine
Archipelago. It stands alone in having an oval,
longitudinally-ribbed fruit with a tough, leathery shell, not a hard,
woody shell as in all the other genera of the subtribe.
Then, too, the locule walls are lined with large mucilage glands that
probably discharge into the seed cavity the mucilaginous material in
which the seeds are embedded. No such mucilage glands have
yet been found in other genera of the Balsamocitrinae, but they may
occur in less striking form in the thick locule walls of Aegle and possibly other genera of this subtribe. The seeds of Swinglea glutinosa are densely woolly, much like those of the Indian bael fruit, Aegle marmelos. The two genera, however, differ greatly in other important taxonomic characters.29
All species of Citrus so far tested graft readily on young rapidly growing seedlings of tabog (Swinglea)
used as a rootstock and reach large size if planted in soil that stays
warm the year round, as for instances greenhouses. Citrus
does not make a vigorous growth when grafted on any other genus
belonging to the subtribe Balsamocitrinae. This would seem
to indicate that Swinglea is more closely related to Citrus than are the other members of the subtribe.
XXVII. Swinglea Merrill
XXVII. Swinglea Merrill, Jour. Arnold Arbor. 8:131. 1927. Chaetospermum (Roem.) Swing. Jour. Wash. Acad. Sci. 3:101. 1913, non Saccardo, Syl. Fungor. 10:706. 1892; Limonia subg. Chaetospermum Roem. Syn. Hesper. 1:39. 1846. Illus. Tillson & Bamford, Amer. Jour. Bot. 25:786, fig. 46. 1938; fig. 3-51 this work.
Type species.—Limonia glutinosa Blanco = Swinglea glutinosa (Bl.) Merr.
Distribution.—Philippines: Luzon Island.
Common name.—Philippine tabog or swinglea.
In 1913, Swingle published a description of this genus under the name Chaetospermum as follows: "A genus related to Belou [= Aegle],
from which it differs in having persistent leaves with small rounded
sessile lateral leaflets, fewer stamens (twice as many as the petals),
fewer ovarial locules (8 to 10), an oblong ribbed fruit with a thick
leathery rind and cells [locules] lined with a spongy tissue containing
many large cavities or vacuoles.
"Leaves persistent, trifoliate,
lateral leaflets small, sessile, usually less than one-third as long as
the median, more or less blunt at the base or even rounded.
Terminal leaflet gradually narrowed at the base. Petioles narrowly winged with a joint at the point of attachment of the leaflets. Spines slender, straight, sharp, in pairs at the axils or else one of the spines is replaced by a branch. Inflorescences axillary, composed of from one to several flowers on rather long, slender pedicels. Flowers perfect, 5-merous; calyx 5-lobed, petals 5, stamens 10, free. Pistil with a well developed style and a thick rounded stigma. Ovary with 8 to 10 cells [locules], each containing numerous ovules. Fruit
oblong, longitudinally ribbed, with a very thick leathery rind, and
with cells [locules] (filled with gum ?) surrounded with watery tissue
containing large cavities or vacuoles. Seeds numerous in the long narrow cells, flattened ovate, hairy. Germination—cotyledons
aerial, not increasing in size; first foliage leaves opposite, broadly
ovate, subseriate, sessile, abruptly narrowed at base." (Fig. 3-51.)
This genus differs rather widely from the
other genera of the Hard-Shelled Citroid Fruit Trees (subtribe
Balsamocitrinae) in having ellipsoid, or ovoid, ribbed fruits with a
leathery outer shell showing very long, pointed, radially arranged oil
glands in the peel and thick tissue containing mucilage glands lining
the radial walls of the segments surrounding the seeds. Its
paleate seeds resemble somewhat the woolly seeds of Aegle, and its trifoliolate leaves have a general similarity to those of Aegle, Balsamocitrus, and Afraegle, but its fruits differ widely in structure from those of other members of the subtribe.
Swinglea makes a good rootstock for Citrus if planted in soil that is always warm; it is a much better rootstock for Citrus
than any other Hard-Shelled Citroid Fruit Tree that has been tested so
far. Another indication of the rather close relationship of Swinglea to Citrus and
the five other closely related genera constituting the True Citrus
Fruit Trees is that it is the only genus outside of this group that is
attacked in the wild state by citrus canker, a disease caused by the
bacterial parasite Pseudomonas citri. Lee (1918, p. 664) stated concerning Swinglea glutinosa,
which grows naturally and is also cultivated at the Lamao Experiment
Station near Manila, P.I., not far from a large collection of Citrus species and cultivated varieties: "The susceptibility of C. [haetospermum = Swinglea] glutinosa to canker is easily greater than that of the sweet orange (Citrus sinensis) in the Philippines." It should be remarked that no natural infections were observed on any of the many other Citrus
relatives under observation with respect to their susceptibility to
citrus canker, although some of them showed slight susceptibly when
inoculated by the needle-prick method (see Lee, 1918; Peltier and
Frederich, 1920).
It must be remembered that the true taxonomic position of Swinglea is still somewhat in doubt and that it may prove to be rather closely related to the Primitive Citrus Fruit Trees, of which Hesperethusa and one species of Pleiospermium also show a certain degree of relationship to Citrus by being attacked, in the wild state, by a fungus belonging to the genus Elsinöe, closely related to E. fawcettii Jenkins that causes scab or verrucosis on several species of Citrus.
Burkillanthus, another of the Primitive Citrus Fruit Trees, of the subtribe Citrinae, shows striking similarities to Swinglea
in its large fruits with stiff leathery rinds, its frequently
trifoliolate leaves, and in the size, shape, and structure of its flower
parts; but it differs widely from Swinglea in the anatomy of its
fruits and in its seeds. It would be very desirable to make
comparative studies of the development of the fruits of Burkillanthus and Swinglea and to make grafting tests in order to determine the degree of relationship of these two curious and little-known genera.
Swinglea glutinosa (Blanco) Merr. Jour. Arnold Arbor. 8:131. 1927. Limonia glutinosa Blanco, Fl. Filip. 358. 1837; Feronia ternata Blanco, Fl. Filip. 2:252. 1845; Aegle decandra Naves apud F.-Villar, Nov. App. in Blanco, Fl. Filip. 38. 1880; A. glutinosa (Bl.) Merr. Phil. Gov. Lab. Bur. Bul. 6:12. 1904; Limonia engleriana Perk. 1905; Belou glutinosa (Bl.) Skeels, U.S. Dept. Agr. Bur. Pl. Ind. Bul. 162:26. 1909; Chaetospermum glutinosum Swing. Jour. Wash. Acad. Sci. 3:102. 1913. Illus. Naves, in Blanco, Fl. Filip. 2:pl. 124. 1880; Vidal & Soler, Sinop. Fam. Gen. Pl. Leñosas Filip. Atl. pl. 25, fig. J(1-5). 1883; Swingle, Bul. Soc. Bot. France 58(mém. 8d):pl. 5. 1912; fig. 3-51 this work.
Type.—Wanting. Substitute type: (Merrill, Plantae Blancoanae, No. 607). Herb. Bur. Sci., Manila.
Distribution.—Philippines: Luzon Island.
Common name.—Tabog or swinglea. Native name: Tabog or boyag (in Tagalog language, Philippines).
Blanco's original description of this
plant follows (translated from the Spanish): Trunk with large solitary
spines. Leaves alternate, ternate. Leaflets
lanceolate, emarginate, shining, the central one largest.
Calyx with 5 teeth. Corolla with 5 thick linear petals, much
longer than the calyx. Stamens 10. Ovary
cylindrical. Style and stigma thick. Fruit
oblong (3 in. [7.6 cm] long and more than 2 in. [5 cm] thick) with
protuberances and confused furrows on the surface, with about 10 locules
and some seeds in each, obovate compressed, ending in a tuft of
wool. Tree 8-10 yards high, [trunk] not very
thick. It is used for pillars in houses. The
fruit is aromatic and the juice sour. It is like a lemon and
is used for 'cola.' I saw it on Mt. Arayat.
Flowers in Dec. [Spanish name] Mala cabuyao, Phil. name
Tabog."
This original description may be
supplemented from herbarium material from Luzon Island, P.I., and from
living plants in the greenhouses of the U.S. Department of Agriculture
as follows: Small or medium-sized tree; twigs angled when young and
finely pubescent, soon becoming terete and losing pubescence; spines
finely pubescent, 1 or 2 in the axils of the leaves, especially on young
vigorous shoots (flowering twigs frequently spineless); leaves
3-foliolate, terminal leaflets 8-12 X 3-5 cm, oblanceolate, bluntly
pointed or sometimes rounded at the apex, gradually narrowed into an
acuminate, finely pubescent base which is not, however, differentiated
into a petiolule, although winged for 1/2-1 cm and articulated by means
of a pulvinus-like base, lateral leaflets oval or obovate, 2.5-5 X
1.2-2.5 cm, 1/5-1/2 the length of the terminal one (never more than half
as long as the terminal one!), bluntly cuneate and pubescent at base
with a very short pulvinoid petiolule, 1-1.5 mm long, not articulated
with the blade, but distinctly articulated with the petiole which is
extraordinarily variable in length (0.5-5 cm), flattened above, finely
pubescent, very narrowly winged; flowers solitary or in clusters in the
axils of the leaves, or sometimes terminal on short twigs leafy at the
base; buds long, elliptical, 6-7 X 3-3.5 mm; calyx 2.5-3.5 X 1.5-2 mm,
cup-shaped, with 5 blunt lobes; corolla white, petals 5, 12-14 X 3-3.5
mm (in dried specimens); stamens 10, filaments filiform, glabrous,
anthers linear, 3.5-4 X 1 mm; pistil 7.5-9 mm long, ovary short-stalked,
obovate, pilose with stiff, yellowish-gray, bristling hairs, style
slender, 0.6-0.7 mm diam., sparingly hairy (hairs like those on the
ovary), twice as long as the ovary, longitudinally furrowed (showing
8-10 furrows), stigma 1.3-1.6 mm diam., flattened like a mushroom,
apparently faintly 10-furrowed; young fruit showing the persistent
style; mature fruit oblong-ovoid, 5-10 X 3-6 cm, locules 8-10; segment
wall thickened, containing numerous large, elliptical mucilage glands;
seeds woolly, several in each locule, surrounded by glutinous pulp; peel
leathery with long, pointed, radially arranged oil glands.
The fruit of Swinglea shows
remarkable structures, here called tentatively mucilage glands, that
seem to arise lysigenously, just as do the oil glands of the peel,
leaves, et cetera. These ellipsoid lysigenous mucilage
glands arise rather close together in the thick locule walls, both
dorsal and radial. Those on the outer portions of the radial
walls slant obliquely away from the middle of the locule walls to the
membrane that lines the narrow seed cavity at an angle of about 45° to
the radial walls. Consequently the mucilage glands in the
radial walls of adjoining locules are disposed at right angles to one
another in a sort of herringbone pattern; at any rate they are thus
disposed in young fruits when all the glands in the locule walls are
nearly equal in size before the growing seeds have more or less
displaced and distorted the glands nearest the axis of the fruit.
It is not impossible that similar, less
evident, structures will be found in the thick radial locule walls of Aegle. The thin (2 mm) radial locule walls of Aeglopsis show numerous but very different glands that secrete mucilage, as described by Chevalier in Swingle (1912b, p. 241, pl. 3, fig. 3). At any rate the mucilage glands of Swinglea are of such large size (5 to 10 by 2 to 3.5 mm) that they cannot be overlooked (see fig. 3-51).
The floral anatomy of Swinglea was
found by Tillson (1938, pp. 22, 30, fig. 46; also Tillson and Bamford,
1938, pp. 789, 790) to be markedly different from that of the other
genera of the Hard-Shelled Citroid Fruit Trees of the subtribe
Balsamocitrinae in that the lateral sepal bundles are fused as they
leave the axis with the petal midrib bundles. This
remarkable condition has also been found in the five genera of the
Primitive Citrus Fruit Trees, in the species of Citrus belonging to the subgenus Citrus, and in Paramignya and Luvunga, all belonging to the tribe Citreae.
The tabog, as this species is called in
the Philippines, is a small thorny tree widely distributed in Luzon
Island. It was found impossible to top-graft Citrus
scions on tabog trees growing out of doors at Manila, P.I., but in the
Washington, D.C., greenhouses of the U.S. Department of Agriculture
vigorous young seedling tabog plants took Citrus buds very well, and these buds continued to grow vigorously and to flower and fruit freely for many years.
From the extraordinary energy of root
growth of the tabog observed in greenhouse sections kept at very high
temperatures (up to 32.2° C, or 90° F), it seems probable that the tabog
requires higher soil temperature during the winter than is found in the
citrus-growing regions of the mainland of the United States except in
extreme southeastern Florida, where the tabog has made a very good
growth in the sandy-loam and porous-limestone soil characteristic of the
Miami region and has withstood temperatures as low a 35° F without loss
of its leaves. In the Panama Canal Zone in the Experiment
Gardens at Summit, the tabog was reported by J. E. Higgins to make a
strong tree that fruited freely and yielded abundant viable
seeds. Since World War I, the tabog has been introduced to
many countries in tropical Central and South America, where it grows
vigorously at altitudes of 1,500 meters or less (fig. 3-52).
This species should certainly be given serious consideration as a rootstock for Citrus
to be grown in greenhouses where the temperature is warm all winter,
and it should also be tested in tropical regions having high soil
temperatures throughout the year.
GROUP B. THE BAEL-FRUIT GROUP
The genera of this group (Aegle, Afraegle, Aeglopsis, and Balsamocitrus)
represent the typical Hard-Shelled Citroid Fruit Trees and are
obviously closely related to one another in spite of their discontinuous
distribution, Aegle being limited to southeastern Asia and
neighboring East Indian islands and the other three genera to tropical
and warm subtropical Africa. All four genera have rather
large fruits varying from the size of a small orange (Aeglopsis) to the size of a small pummelo (Aegle and Balsamocitrus).
All the genera of group B have fruits with a dense, hard, woody rind
without longitudinal ridges like those found in the leathery rind of the
tabog (Swinglea) of group A, and also without any sign of radially arranged shoe-peg-like elements, such as constitute the woody rind of Feroniella.
Although all four of the genera that
constitute the Bael-Fruit Group have fruits resembling those of Citrus
in size, in the number of follicles, and in the number and arrangement
of the seeds, none show any sign of the highly developed pulp-vesicles
that characterize Citrus and the other genera of the True Citrus Fruit Trees. None of the Bael-Fruit Group will hybridize with Citrus. However, they have been successfully grafted on Citrus species under greenhouse conditions at the Citrus Research Center in Riverside, California.
XXVIII. Aegle Corrêa
XXVIII. Aegle Corrêa, Trans. Linn. Soc. 5:222. 1800. Belou Adans. Fam. 2:408. 1763.
Type species.—Crataeva marmelos L. = Aegle marmelos (L.) Corrêa.
Distribution.—India: wild in large
colonies in northern India up to 1,219 m, also in central and southern
India and Burma; widely cultivated in southeastern Asia and in the East
Indian Archipelago.
Common name.—Indian bael fruit.
A thorny tree with deciduous, dimorphic
3-foliolate leaves; leaflets crenate, articulated with the petiole, thin
and of soft texture, with numerous translucent oil glands;
inflorescences axillary, loosely branched; pedicels shorter than the
petals; flowers large; calyx deciduous, small, saucer-shaped, with 4-5
short, blunt lobes; petals 4-5, large, imbricate, long-ovate, with
bluntly rounded apices; stamens very numerous, with subulate filaments
and long, linear anthers; disk small, annular; ovary cylindric, with
8-20 locules, each containing numerous ovules in 2 rows; ovary tapering
slightly toward the top and somewhat narrowed into the style, which is
about 1/4 or 1/5 as long as the ovary; stigma with longitudinal furrows,
cylindrical or bluntly conical, slightly wider than the style; fruits
globose or subglobose with a very hard, woody shell, segments 8-16 or
more (Talbot, 1909, p. 205, stated: "8-20"), narrow, filled with 6-10 or
more seeds imbeded in transparent glutinous gum, lateral walls of the
segments thickened and fleshy; seeds oblong, slightly flattened, woolly,
monoembryonic; cotyledons hypogeous in germination.
The genus Aegle is one of the three monotypic genera of the orange subfamily (Poncirus and Feronia are the other two) with deciduous leaves. Two other genera of the subfamily, Clausena and Murraya, have deciduous-leaved species: Clausena has three species (C. pentaphylla, C. dentata var. dulcis, and C. suffruticosa) and Murraya has one species (M. alternans).
Aegle is obviously related to the genera Balsamocitrus, Afraegle, and Aeglopsis of
tropical Africa but differs from all of them in having very numerous
(30 to 40 or more) stamens (6 to 8 times as many as the petals) and very
numerous (8 to 16 or more) locules in the ovary, and also in having
woolly seeds. It is a highly specialized genus having a
certain degree of resistance to cold.
Aegle marmelos (L.) Corr. Trans. Linn. Soc. 5:223. 1800. Crataeva marmelos L. Sp. Pl. 444. 1753; Belou marmelos (L.) Lyons, Plant Names 69. 1907. Illus. Roxburgh, Pl. Corom. 2:pl. 143. 1798; Wight, Icon. Pl. Ind. Or. 1:pl. 16. 1840; Bentley & Trimen, Med. Pl. 1:55. 1880; Wilkins, Hindu Myth. 390. 1882; Bonavia, Cult. Orang. Lem. Ind. Cey. Atl. pls. 242, 243. 1890; Beddome, Fl. Sylv. 1:pl. 121. 1869; Turner, Agric. Gaz. N. S. Wales 4:pl. 14. 1893; fig. 3-53 this work.
Type.—Ceylon [cult.] (Hermann). Herb. Brit. Mus., London.
Distribution.—India, Burma,
Thailand (?), Indo-China (?); widely cultivated in southeastern Asia and
the East Indian Archipelago; native in northern India, often growing in
large groups, up to 1,219 m altitude (4,000 ft); also native in central
and southern India and Burma.
Common name.—Indian bael fruit.
Bentley and Trimen (l.c.) gave the
following description of this species: "A tree reaching a height of 30
or 40 feet when cultivated, with a short thick trunk and narrow oval
head; in the wild state smaller and more irregular, with short, strong,
sharp, spiny branches 1 inch or more in length in the axils of the
leaves; bark bluish-grey, soft, with irregular furrows on the younger
branches. Leaves alternate, compound, with one (rarely 2)
pairs of shortly stalked opposite leaflets, and a larger long-petioled
terminal one, leaflets 1-2 inches long, ovate or oval-ovate, abrupt or
tapered at the base, somewhat attenuated towards the blunt apex, very
shallowly serratocrenate, smooth, thin, midrib prominent
beneath. Flowers 3/4 inch wide, sweet-scented, stalked,
solitary, or in few-flowered, lax, erect, axillary or terminal
cymes. Calyx shallow, with 5 short, broad teeth, pubescent
outside. Petals 5 (rarely 4), oblong-oval, blunt, thick,
pale greenish-white, dotted with glands, imbricate,
spreading. Stamens numerous, sometimes coherent in bindles,
hypogynous with short filaments half as long as the linear
anthers. Disk none or very small. Ovary
oblong-ovoid, slightly tapering into the thick short style which is
again somewhat thickened upward, stigma capitate, axis of ovary wide,
cells numerous, 8-20, small, arranged in a circle, with numerous ovules
in each cell. Fruit usually globose, 2-5 inches in diameter,
pericarp nearly smooth, greyish-yellow, about 1/8 inch thick, hard,
filled with softer tissue becoming very hard and orange-red when dry;
cells as in ovary. Seeds very numerous, somewhat compressed,
ranged in closely packed tiers in the cells and surrounded by a very
tenacious, slimy transparent mucus which becomes hard when dry; testa
white, covered with woolly hairs immersed in the mucus, embryo with
large cotyledons, and a short superior radicle; no endosperm."
Aegle marmelos has dimorphic twigs: (a)
normal twigs with internodes 3 to 5 cm long with one well-developed
leaf at each node, often with one or two spines alongside; (b)
foliage spurs produced on primary branches of the previous year's
growth, usually very short, 1 to 3 cm long, with numerous very short
internodes, each node bearing a leaf but no spines. The
numerous leaves crowded on the foliage spurs vary greatly in size, the
largest being nearly as large as the normal leaves on rapidly growing
long-internoded branches but having decidedly longer
petioles. The smaller leaves borne near the base of the
foliage spurs are often much dwarfed, sometimes being only one-fifth or
one-tenth as long as normal leaves. These crowded leaves of
all sizes often hide almost completely the branches which bear them.
Because of these dimorphic
characteristics the bael-fruit tree presents a peculiar appearance, with
its long, slender young branches with only a few leaves scattered along
them arising from an inner crown of older branches almost completely
covered with massed foliage borne on the leaf spurs. Poncirus trifoliata
has somewhat similar dimorphic branches and leaves but shows much less
variation in the size of the leaves produced on the leaf spurs.
Besides this dimorphism of twigs and leaves, Aegle marmelos
shows great variability in both kinds of leaves on different seedling
trees, not only in size but in important botanical characters, such as
the presence or absence of a separative layer at the junction of the
terminal leaflet with its petiolule, the relative length of this
petiolule and of the petiole, as well as the length of the petiole in
relation to the length of the entire leaf. The petioles on
some trees have distinct wings on each side for almost their entire
length and on other trees show only two inconspicuous green lines
broadened into very narrow wings at the upper end of the
petiole. The leaflets vary greatly on different seedling
trees in marginal crenulation and flatness or curvature of their
surface. There is also great variation in the posture of the
leaves on the twigs which bear them and the degree to which the blades,
petioles, and supporting twigs show reddish coloration where exposed to
sunlight.
These surprising diversities in leaf
characters were studied by Swingle in October, 1941, on some thirteen
fruiting trees growing at Coconut Grove and Homestead, Florida, and
convinced him that it would be necessary to make a detailed study of
both wild and cultivated bael-fruit trees in India. The
extraordinary variation in taxonomically significant characters shown by
the trees grown from seeds imported from India very probably means that
there are several different strains, botanical varieties, or even good
species to be found among the wild plants growing in the mountains of
northern India. Seedlings of these diverse wild forms
planted together in the villages would doubtless be cross-pollinated by
insects and produce complex and highly variable hybrids like those we
find growing in Florida.
For many years few or no fruits of Aegle marmelos
were produced by trees growing in the continental United States, but
now the trees in southern Florida have fruited freely. S. J.
Lynch, former horticulturist of the Subtropical Branch Station of the
Florida Agricultural Experiment Station at Homestead, found that many
bael-fruit trees in southern Florida were suffering from zinc
deficiency. Application of small amounts of zinc sulphate
caused them to make a vigorous new growth with green (not yellowish)
leaves and favored the setting and maturing of a good crop of fruit.
The Hindus esteem the ripe bael fruit
very much; in fact, many of them consider it to be the best of the
citrus fruits. Some European residents of India have been
known to develop a decided liking for it. Watt stated (1889,
vol. 1, p. 123): "The fruit, when ripe, is sweetish, wholesome,
nutritious, and very palatable, and eaten by all classes.
The ripe fruit diluted with water, forms with the addition of a small
quantity of tamarinds and sugar, a delicious and cooling
drink." Concerning its medical value, W. R. Mustoe, then
superintendent of the Government Archipelago Gardens, Lahore, India,
wrote to David Fairchild on December 3, 1908, as follows: "All Indian
medical authorities agree that the Bael fruit has a most salutory
influence on the digestive system. The ripe fruit is mildly
laxative and is a good simple remedy for dyspepsia. The
unripe fruit is a specific of the highest value for dysentery so mild
that it can be given to children without danger." Roxburgh
stated (1795-1819, vol. 2, p. 23, pl. 143): "The fruit, delicious to the
taste and exquisitely fragrant, is not only nutritious, but possesses a
laxative and aperient quality, confirmed by experience, which renders
it particularly serviceable in habitual costiveness."
The wild forms of Aegle marmelos have
small fruits (5 to 7.5 cm in diameter), whereas in cultivated forms the
fruits may attain a diameter of 12.5 to 17.5 cm (see fig. 3-53).
According to Davis (1930, p. 111), in its wild or semi-wild state the
bael-fruit tree grows freely in the Bahraich Forest in northern India
(one of the northern districts of Oudh, in Uttar Pradesh State to the
south of Nepal), even on poor clay soils where other trees
fail. In view of the widespread use of the fruit in India
both for food and for medicine, it is very desirable that this species
be tested in the United States. Fortunately it is easily
propagated from seed and from layers. According to Turner
(1893, p. 152), A. marmelos has been successfully fruited in
northeastern New South Wales as far south as the Clarence River (about
Lat. 29° 30' S.). It has for some time fruited in the warmer
parts of the United States, and it is almost certain to succeed in
Puerto Rico and Hawaii. In extreme southeastern Florida this
species has been grafted successfully on Aeglopsis chevalieri and on Afraegle gabonensis,
both of which are rather closely related plants that grow vigorously in
the sandy-loam, porous-limestone soils found in this region.
Although the bael-fruit tree grows
commonly in tropical climates, it loses its leaves in winter when in a
cool climate; moreover, it is able to endure low temperatures in India
when in a leafless condition—as low, it is said, as 17.5° F (-8°
C). It is possible that, like many other deciduous trees, it
must be exposed to the proper degree of cold over a long enough period
for food materials stored in the trunk and twigs to be rendered
available to support the new growth in early spring.
XXIX. Afraegle (Swing.) Engler
XXIX. Afraegle (Swing.) Engler, Die Pflanzenwelt Afrikas 3:761. 1915. Balsamocitrus Sec. Afraegle Swing. Bul. Soc. Bot. France 58(mém. 8d):233. 1912.
Type species.—Citrus paniculata Schum. = Afraegle paniculata (Schum.) Engl.
Distribution.—West Africa: Ghana, Togo, Dahomey, Nigeria, Cameroon, Gabon, Fernando Po Island.
Common name.—African powder-flask fruits.
Swingle described Afraegle as a section of Balsamocitrus in 1912 and at the same time established the section Eubalsamocitrus for the typical species, B. dawei. The section Afraegle
was raised to generic rank in 1915 by Engler. In his
revision of the whole plant family Rutaceae, Engler described it (1931,
p. 352) as follows (in translation): "Calyx small, 5-merous,
persistent. Petals 5 linear, imbricate. Stamens
about 20 with subulate filaments and anthers of about equal length,
inserted in a broad lobed disk. Ovary short-ovate, roughened
with glands, with about 8 locules, more or less, with numerous ovules
in each locule; style shorter than the ovary with a long-ovate
stigma. Fruits large, globose or pear-shaped, with a hardish
shell, many-seeded. Seeds large, up to 1.7 cm long, 1 cm
thick, ovate, or wedge-shaped at the base, rounded or bluntly
angled. Trees with trifoliolate, long-slender leaflets
narrowed toward both ends, with axillary thorns and small 6-10-flowered
racemes."
This West African genus of Hard-Shelled
Citroid Fruit Trees contains three or four species of medium- or
large-sized trees, including A. (?) asso, the tallest African species of the orange subfamily. Afraegle is more advanced from an evolutionary point of view than Balsamocitrus in that it has stamens three to four times as numerous as the petals (instead of only twice as many). Afraegle is related to Aeglopsis; the latter, however, has simple leaves and only six locules in the ovary, instead of eight to ten, as in Afraegle. A key to the species of Afraegle is presented.
1. Afraegle paniculata (Schum.) Engl. Die Pflanzenwelt Afrikas 3:761. 1915. Citrus paniculata Schum. Dan. Vid. Selsk. Afh. 4:153. 1827; Aegle barteri Hook. f. 1895; Limonia warneckei Engl. 1905; Balsamocitrus paniculata (Schum.) Swing. Bul. Soc. Bot. France 58(mém. 8d):231. 1912. Illus. Hooker f., Icon. pl. 2285. 1895; Swingle, loc. cit. pls. 1, 2. 1912; idem, in Bailey, Stand. Cycl. Hort. 1:444, fig. 455. 1914; Engler, loc. cit. 1915; idem, in Die Nat. Pflanzenfam. 19a:351, fig. 161. 1931; Tillson & Bamford, Amer. Jour. Bot. 25:786, figs. 39-45. 1938; fig. 3-54 this work.
Type.—West Africa, Gold Coast (Thonning, No. 179 ?). Herb. Copenhagen (?). Cotype: Herb. Jussieu, Mus. Hist. Nat., Paris.
Distribution.—West Africa: Liberia (?), Ivory Coast, Ghana, Dahomey, Nigeria.
Common name.—Nigerian powder-flask fruit.
In 1912 Swingle quoted a detailed
description of this plant by Chevalier. It reads as follows
(in translation from the French): "Tree 8-15 m high, branching 1.5-2 m
above ground. Trunk 25-40 cm diam., bark brown, lightly
split longitudinally. Branches numerous, spiny, making a
rounded head like an orange tree. Young twigs green,
slender, glabrous, spines straight, very sharp, 12-18 mm long, occurring
in the axils of some leaves.
"Leaves alternate, 3-foliolate or, by
exception, 1-foliolate by abortion, 8-16 cm long, completely
glabrous. Leaflets similar, oboval or oblong, cuneiform at
base, rounded or alternate, subacute at the apex, sometimes retuse,
lightly crenulate in the upper half or 2/3 of the margin, firm or
subcoriaceous, a beautiful green color both above and below, central
leaflet a little larger than the lateral ones, measuring 4.5-11 cm long
and 2.5-5.5 cm broad, borne on a petiole 5-30 mm long, articulated at
the two ends, lateral petioles 2-10 mm long. Inflorescences
small, axillary panicles, 4-6 cm long, few-flowered (6-10 fls.),
isolated at the axil of the leaves or inserted on parts having already
lost their leaves. Rachis and pedicels glabrous green,
pedicels 2-3 mm long. Flowers white, with a strong odor of
'berlingot,' glabrous, buds ovoid. Calyx cyathiform, 3-4 mm
long with 4 short lobes rounded and irregular. Petals 4,
oval, oblong, rounded at the apex, greenish outside, white inside, 10-13
X 4-6 mm, curved backward. Stamens 15-20 (usually 16),
filaments free, white, fusiform, erect, 4-5 mm [long]; anthers oblong,
2.5 mm long. Disk greenish-stipulate, slightly
lobed. Ovary ovoid, greenish, divided into ±8
locules. Stigma ovoid, glandular, 3 mm long, borne on a very
short style.…
"Fruit globose or obovoid, sometimes
slightly stipulate at base, almost always depressed at the top, as large
as a big orange (6-8 cm diam. when mature), wrinkled on the surface,
sometimes tuberculous, without odorous glands.
"Pericarp hard, 4-5 mm thick, resembling the pericarp of large fruited Strychnos, remaining green when mature, then becoming grayish.
"Segments 8 (!) with smooth walls (not
covered with fleshy hairs). Each segment contains numerous
seeds irregularly arranged in 2 or 3 rows, inserted in the placenta,
axillary and in orderly arrangement, tegument whitish, parchment-like."
Fresh flowers of Afraegle paniculata from a tree grown in the citrus greenhouse of the former Bureau of Plant Industry at Washington, D.C. (see fig. 3-54), were compared on July 10, 1937, with fresh flowers of A. gabonensis grown in the same greenhouse. They showed the following points of difference: Inflorescences of A. paniculata much longer, but pedicels slightly shorter (3 to 4 mm long); flowers about the same size as those of A. gabonensis;
calyx not flat and discoid but cup-shaped with 3 to 5 clearly marked,
very bluntly pointed lobes, finely ciliate at the apex; petals very
similar to those of A. gabonensis; stamens similar but in A. paniculata nearly four times as numerous as the petals (often one or two short of this number), whereas in A. gabonensis three
times as many (or a few short); disk smaller, about 3.5 to 4.5 mm wide
and 1.5 mm high, pea-green instead of yellowish-green, as in A. gabonensis.
This tree, which reaches a height of 15
meters, is often planted by the natives in their villages in Dahomey and
Nigeria. The seeds are said to yield an edible oil and the
leaves are sometimes macerated and added to the water used for
bathing. In the United States, this species grows well in
the greenhouses of the U.S. Department of Agriculture and sometimes
flowers, but so far has not borne fruit. In the
quasi-tropical coastal region near Miami, Florida, which has an unusual
type of soil consisting largely of porous-limestone rock intermingled
with fine sand or very sandy loam, this species, when well fertilized,
makes extraordinary growth—probably ten times as fast as in the
Washington greenhouse. A tree growing near Coconut Grove,
when only four or five years old and only 5 feet (1.6 to 1.8 m) high,
had a lateral spread of 15 to 20 feet (4.5 to 6 m). As it
grew older, this tree became much taller but still had long
branches. Afraegle paniculata grows in the Miami region much more rapidly than Aeglopsis chevalieri (another
vigorous but dwarfish West African Hard-Shelled Citroid Fruit Tree),
and is being tested as a rootstock for the bael fruit Aegle marmelos, a species which often does not grow well on its own roots.
2. Afraegle gabonensis (Swing.) Engl. Die Pflanzenwelt Afrikas 3:761. 1915. Balsamocitrus gabonensis Swing. Bul. Soc. Bot. France 58(mém. 8d):233. 1912. Illus. Swingle, loc. cit. 58(mém. 8d):235, fig. B, pl. 4.
Type.—West Africa, Gabon (Congo
française) (R. Père Klaine, No. 2008); plant grown from seed of this
collection in greenhouse of Jardin des Plantes at Paris was for many
years grown in the citrus greenhouse of the former Bureau of Plant
Industry, Washington, D.C. (C.P.B. No. 7516). Natl. Herb.,
Washington, D.C. Cotype: Gabon du Nord (R. Père Klaine, No. 1106, fruit with seeds). Herb. Mus. Nat., Paris.
Distribution.—West Africa: Gabon.
Common name.—Gabon powder-flask fruit.
Swingle's original description of this
species reads as follows (in translation): "Balsamocitrus with simple or
3-foliolate leaves, lateral leaflets much shorter than the terminal one
(never half as long), lanceolate or narrowly lanceolate, more or less
acute at the apex, acute at the deltoid base, margin almost entire or
slightly crenate, densely glandular-punctate; petioles winged, 0.5-3.5
cm long in 3-foliolate leaves, much longer than in 1-foliolate ones,
very glabrous, flattened above, spines slender; sharp, solitary or in
pairs in the axils of the leaves, scarcely as long as the petioles, 1-2
cm long or very slightly recurved. Flowers
unknown. Fruits subpyriform, size of a large orange, cortex
hard, 3 mm thick; seeds numerous, glabrous, oval or cuneiform, more or
less angled, 1 1/2-1 3/4 cm long. 3/4-1 cm wide.
Spiny tree, young twigs virgate green."
Fresh flowers from a tree grown in the
former Bureau of Plant Industry greenhouse at Washington, D.C. (tree
grown from seed sent by R. Père Klaine [No. 2008] in 1892 from Gabon to
Paris, brought to the United States in 1912 by Swingle [l.c.]), were
examined. The inflorescences are short, axillary racemes or
corymbs, pedicels glabrous, 5-7 mm long, 1 mm diam. at base, 2 mm diam.
at junction with the calyx; calyx 3-4 mm diam., thick, flat,
plate-shaped with lobes very faintly or not at all marked, but with a
thin, hyaline, ciliate membrane around the margin (the interruptions in
this membrane probably delimit the poorly defined sepals); bud broadly
conical, 4-5 mm wide and 7-8 mm long, vivid green; petals 3-5, green
without, greenish-white or cream-white where thickest, 9-11 mm long, 3-5
mm wide, ovate-rounded at the tip and slightly acute, curved, strongly
incurved near the apex, soon falling, each carrying 2 stamens attached
at the base; stamens apparently 3 times as many as the petals (9-15),
4-6 mm long, glabrous, subulate, 1 mm diam. at the base, 0.5 mm at
attachment to anthers, which are linear, arising at the base of a very
long lobed disk and curving upward along the furrows in it; disk 5-6 mm
diam., 2-3 mm high, forming a shallow cup in which the ovary fits
loosely; ovary ovate, about 3 mm high, 2 1/2-3 mm wide, with 8 locules;
ovules in each locule numerous, in 2 rows; style very short, thick, 1
3/4 mm wide, 1 mm long, ending in an ovoid glutinous stigma, 2 mm long
and 1 1/2 mm wide.
Afraegle gabonensis, like Aeglopsis eggelingii, has three times as many stamens as petals,30 not twice as many or four (or
more) times as many as do the other species of the
subfamily. This species grows vigorously and fruits
sparingly in the Fairchild Gardens, Coconut Grove, Florida.
IMPERFECTLY KNOWN SPECIES
3. Afraegle asso Engl. Die Pflanzenwelt Afrikas 3:761. 1915.
Type.—Molunda district, southern Cameroons, West Africa. Herb. Bot. Mus., Berlin-Dahlem.
Distribution.—Known only from the type locality.
Engler's short description (l.c.) reads
in translation as follows: "Finally there is found in the District
Molunda, in South Kamerun, a tree up to 30 meters [98 1/2 ft.] high,
with broadly ovate leaflets and large fruits."
According to Engler, this species and A. milbraedii may belong to Balsamocitrus instead of to Afraegle, as flowers (necessary to decide to which genus they belong) are still unknown.
4. Afraegle milbraedii Engl. Die Pflanzenwelt Afrikas 3:761. 1915.
Type.—San Carlos, Fernando Po Island, West Africa. Herb. Bot. Mus., Berlin-Dahlem.
Distribution.—Known only from the type locality.
Engler gave (l.c.) a very brief notice of this species as follows: "[Afraegle gabonensis] is rather closely approached by A. Milbraedii from San Carlos on Fernando Po, of which unfortunately we have only imperfect specimens; it is distinguished from A. gabonensis
by leaflets that are more linear than lanceolate but more strongly
narrowed into the petiolule at the base, and finely crenulate on the
margins; the pear-shaped, hard-shelled fruits are unfortunately not
developed normally." Since Engler (1931, p. 353), shortly
before his death, reprinted this unchanged, evidently no additional
material had been obtained.
XXX. Aeglopsis Swingle
XXX. Aeglopsis Swingle, Bul. Soc. Bot. France 58(mém. 8d):237. 1912.
Type species.—Aeglopsis chevalieri Swing.
Distribution.—West Africa: Ivory Coast.
Common name.—Dwarf powder-flask fruit.
Much branched, very spiny small tree or
shrub; leaves simple, subcoriaceous, pellucid-punctate; petioles short,
spines solitary, axillary; inflorescences axillary panicles, few- or
many-flowered; flowers 4-5-merous; stamens 2 or 3 times as many as the
petals; style very short, stigma cylindric, viscous; disk large, lobed,
sulcate, annular, enclosing the ovary, which has 6-8 (rarely 5) locules,
ovules 12-18 (?) in each locule; fruit subglobose or pyriform, 5-11 cm
long, 4-8 cm diam., size of an orange, with a hard, woody shell, filled
with mucilaginous juice; seeds ovate-compressed, with a coriaceous,
glabrous testa.
This genus of two species, one found in
the Ivory Coast region of West Africa and the other one in Uganda and
Sudan in East Africa, is doubtless closely related to Afraegle, Balsamocitrus, and Aegle.
It is the simplest form of all this group of Hard-Shelled Citroid Fruit
Trees in that it has fewer locules in the ovary (6 to 8 instead of 8 to
20); moreover, it has twice or three times as many stamens as petals, a
somewhat primitive character in the orange subfamily. It
shows, however, an advanced character in its invariably simple leaves
(even the first two opposite pairs of post-cotyledonary leaves are
simple). A
key to the species of Aeglopsis appears below.
1. Aeglopsis chevalieri Swing. Bul. Soc. Bot. France 58(mém. 8d):240. 1912. Illus. Swingle, loc. cit. pl. 2, figs. 1-9, and pl. 3; idem, in Bailey, Stand. Cycl. Hort. 1:223, fig. 130. 1914; fig. 3-55 this work.
Type.—Port de Sassandra, Ivory
Coast, West Africa (Chevalier, No. 17940). Herb. Chevalier,
Herb. Mus. Hist. Nat., Paris. Paratypes: Herb. Mus. Nat., Paris, and Natl. Herb., Washington, D.C.
Distribution.—Collected only along
the Ivory Coast from western Sassandra to the Liberian frontier;
doubtless occurs also in Liberia and in Ghana.
Common name.—Chevalier's aeglopsis.
Shrub or small tree, branches numerous;
spines solitary, straight, strong, pointed, 2-3.5 (sometimes 3-7) cm
long; leaves simple, medium-sized, 5-12 X 2.5-7 cm, elliptical, rounded
at the apex or short-acuminate, cuneate at base and merging gradually
into the short, glabrous, wingless petiole (2-4 mm long), which is not
articulated with the leaf blade; inflorescences small, axillary
panicles, few-flowered (4-8) or sometimes many-flowered (20-40),
pedicels slender (3-5 mm long); flowers glabrous, white, calyx 4-5 mm
diam., with 4-5 short, wide lobes more or less rounded, petals 5
(sometimes 4), white, oblong-lanceolate, rounded at the apex, 9-12 X
3.5-5 mm, caducous, stamens 8-10, filaments free, linear, 5-6 mm long,
anthers oblong, 2.5-3 X 1 mm; disk subcupulate, very large, 5-6 mm
diam., 2.5-3 mm high, with about 10 rounded lobes; ovary ovoid, 2.5-3 X
2-3 mm, merging imperceptibly into the short style, locules 6 (sometimes
5), containing numerous ovules (12-18 ?) arranged in 2 series; fruits
globose or pyriform, attenuate at the base when young, 6-9 cm diam.,
with 6 (sometimes 5) segments, 8-12 seeds in each segment pressed
together and imbedded in a liquid, mucilaginous jelly secreted by the
glands on the locule walls; peel semicoriaceous, green, becoming
yellowish, 3 mm thick, with many nonodorous superficial glands; seeds
ovoid, flattened, 12-16 mm long, 10-12 mm wide, and 4-7 mm thick, with a
parchment-like, glabrous testa.
Aeglopsis chevalieri is the only
Hard-Shelled Citroid Fruit Tree that has flowered and set fruit freely
in the orange house of the U.S. Department of Agriculture at Washington,
D.C., while still a small tree, 2 or 3 meters high (fig. 3-55).
It flowers profusely and bears a few small, pyriform, only moderately
hard-shelled fruits of brilliant orange-brown color. The
seeds germinate freely, but the cotyledons, although turning green,
remain buried in the soil. Seedlings of A. chevalieri planted some years ago in David Fairchild's collection of Citrus
and related plants in his tropical garden, "The Kampong," at Coconut
Grove, Florida, have made a remarkably vigorous growth. They
have flowered profusely and have ripened abundant fruits filled with
good seeds.
Seedling plants of this species, so
easily obtained in quantity, make excellent rootstocks on which to graft
Balsamocitrus, Afraegle,and also Aegle, genera which seldom fruit in the United States and which are also hard to propagate from cuttings. Aeglopsis seedlings were used not only to propagate the rare East African Balsamocitrus dawei by grafting the latter species on the young seedlings but also to induce rooting of Y-cuttings of Balsamocitrus dawei (see Swingle, Robinson, and May, 1929, p. 79).
2. Aeglopsis eggelingii M. R. F. Taylor, Kew Bul. Misc. Inform. 1940:53. 1940.
Type.—Uganda, Bunyoro District
(Lat. 1° 10'-2° 20' N., Long. 30° 40'-32° 25' E.), Siba Forest
(Eggeling, No. 3006). Herb. Kew.
Distribution.—Uganda: between Lake Edward and Lake Albert, Toro District, Bunyoro District; Sudan: Equatoria Province, Lado.
Common name.—Eggeling's aeglopsis.
The original description translated from Latin reads: "Differs from A. Chevalieri Swingle
in its shrubby habit, axillary spines seldom paired, pedicels with
bracts, globose buds, petals 3 or 4, ovate, never lanceolate, stamens 3
times as many as the petals, ovary 7-8-locular, Much-branched [sic]
shrub, 4 m high, spiny, glabrous. Branches rounded,
compressed when young, brownish, internodes 2-4 cm long, spines
axillary, solitary or paired, 2-3 cm long, stiff, erect, spreading;
leaves simple, alternate, subcoriaceous; petioles 5-8 mm long,
canaliculate-pulvinate; leaf blade ovate or ovate-lanceolate, 7-14 cm
long, 3-5.5 cm wide, apex obtuse or acute or often acuminate, cuneate
towards the base, margins slightly and irregularly crenate, dark green
above, pale green below, densely pellucid-punctate on both sides, midrib
prominent, lateral veins 7-10 on each side, spreading, arcuate;
inflorescence axillary, few-flowered (about 5), peduncles irregularly
branched, branchlets very short (up to 3 mm long), pedicels 3 mm long
'ampliati' [swollen above ?], with 2 bracts, glandular-punctate, bracts
ovate-lanceolate, 1 mm long, obtuse; flowers 1.5-2.5 cm diam.,
greenish-white, buds globose or slightly 3-4-lobed, about 4 mm diam.;
petals 3-4, ovate, 1 cm long, 7-8 mm wide, obtuse at the apex, truncate
at base, thick, glandular-punctate, longitudinally striate above,
margins sometimes slightly incurved towards the apex; stamens 9-12 (3
times the number of the petals), filaments strap-shaped, attenuate
towards the apex, about 5 mm long, 1 mm wide, compressed, thick,
incurved; connective glandular at apex; anthers oblong, 2 mm long, about
1 mm wide; disk annular, 5-6 mm diam., 1.5-2 mm high, lobed, sulcate;
ovary ovoid, 3-4 mm long, 2-3 mm diam., base sunk in the disk, locules
7-8, ovules numerous; style 2 mm long, 1 mm diam., rounded; stigma
cylindrical, about 1.5 mm diam.; fruit subpyriform, 9-11 cm long, 7-8 cm
diam., fragrant, 7-locular, locules widely triangular, polyspermous,
peel subligneous; seeds subellipsoid, 1-1.5 cm long, 8 mm wide,
compressed."
William J. Eggeling, who discovered this
species and in whose honor it was named, made an interesting report
about it in a general work on the forest trees of Uganda (1940, p.
205). He stated that it is a spiny bush or tree, growing up
to 20 feet high on the edges of the forest; "spines strong, straight,
sharp, slender 1/3-1/2 in. [8 to 13 mm] long"; also, "fruit
yellow-green, woody, pear-shaped, up to 3 in. diam. [75 mm]; seeds
surrounded by a strongly aromatic balsam."
XXXI. Balsamocitrus Stapf
XXXI. Balsamocitrus Stapf, Jour. Linn. Soc. 37:504. 1906.
Type species.—Balsamocitrus dawei Stapf.
Distribution.—Uganda: a monotypic genus known only from the type locality in the Budongo Forest, Unyoro.
Common name.—Uganda powder-flask fruit.
Stapf's original description of the genus reads, in translation, as follows: "Related to Aegle,
but distinct in habit of growth, in having thick leaves, and chiefly in
having few stamens and the seed with glabrous testa.
Flowers hermaphrodite. Calyx small, 5-merous, persistent for
a day. Petals 5, oblong, imbricate. Stamens 10;
filaments subulate, longer than the sagittate anthers, inserted [sic]
in the annular disk. Ovary ovoid, with 8 locules; style
short, conical-cylindric, soon deciduous; stigma inconspicuous, slightly
sulcate; ovules many in each locule, in 2 series. Fruit
ovoid-globose, with a woody cortex, 8 segments, filled with many seeds
in a liquid balsamic jelly, pulp scarce. Seeds subellipsoid,
slightly compressed, testa coriaceous, very glabrous.
Endosperm lacking. Embryo with large thick fleshy
cotyledons, radicle small. Unarmed tree, tall.
Leaves 3-foliolate, leaflets thick, cortaceous, subcrenulate,
pellucid-punctate. Panicles axillary, short, flowers,
small. Fruit large. One species."
Balsamocitrus is apparently the most primitive of the four closely related genera of Hard-Shelled Citroid Fruit Trees (Balsamocitrus, Aeglopsis, Afraegle, and Aegle). It is like Aeglopsis chevalieri in having only twice as many stamens as petals but, unlike the simple-leaved Aeglopsis,
it retains the trifoliolate leaves undoubtedly ancestral in this group,
and very rarely produces unifoliolate leaves. Balsamocitrus does not show the exuberantly-developed, lobed disk that is found in the other African genera of this group, Aeglopsis and Afraegle, but has a simple, annular disk like the Indian genus Aegle, which, however, differs from all the African genera in having very numerous stamens and woolly seeds.
Balsamocitrus dawei Stapf, Jour. Linn. Soc. 37:504. 1906. Illus. Stapf, loc. cit. pl. 37; Swingle, Bul. Soc. Bot. France 58(mém. 8d):226, fig. A. 1912; idem, in Bailey, Stand. Cycl. Hort. 1:443, fig. 454. 1914; Swingle, Robinson, & May, Jour. Hered. 20(2):figs. 9-12. 1929; Eggeling, Indig. Trees Ugand. fig. 58,a-d. 1940; fig. 3-56 this work.
Type.—East Africa, Uganda, Unyoro, in the Budongo Forest east of Lake Albert Nyanza (Dawe, No. 788). Herb. Kew.
Distribution.—Known only from the type locality.
Common name.—Uganda powder-flask fruit.
The original description, as translated,
reads: "Tree, about 20 m tall, very glabrous. Twigs rather
thick, on drying black, young ones hollow or spongy
('fistulosus'). Leaflets unequal, ovate or ovate-elliptic,
somewhat obtuse, or subacuminate, acute at the base, crenulate, 4-7 cm
long, 3.5-5 cm wide, on drying fuscous, black-punctate; lateral
petiolules 7-10 mm long, intermediate terminal ones up to 15 mm long;
the common petioles 2.5-3 cm long. Panicles 2-4 cm long,
contracted; bracts very small; ultimate pedicels up to 4 mm long, rather
thick. Calyx up to 2 mm long, segments broadly ovate,
acute, somewhat thick. Petals white, 5 mm long.
Filaments 2 mm (or a little more) long; anthers scarcely 1.5 mm
long. Fruit up to 13 cm long, 11 cm wide, cortex 5 mm
thick. Seeds up to 16 mm long, 10 mm wide, 8 mm
thick. Unyoro, Budongo Forest, Dawe 788."
Eggeling, in his work on the forest trees
of Uganda, stated (1940, p. 205): "Deciduous forest tree, 70 ft.;
flowers greenish-yellow in contracted axillary panicle, 2-3 in. [50-75
mm] long, petals 1/5 in. [5 mm] long [sic], very odorous, woody
(shell 1/5 in. [5 mm] thick); yellow-orange when ripe, ovoid globose, up
to 5 1/2 in. [13 cm] diam., 6-8 locules; seeds several per locule,
about 2/3 in. [16 mm] long. Wood yellow-white, even in
grain, hardy, nailing badly but not splitting, difficult to saw, planing
badly, turning well, taking a good polish; weight 52 lbs. per cu. ft.
air-dry."
This remarkable Citrus relative is
native to the plateau of Uganda, East Africa, to the east of Lake
Albert, at altitudes of 600 to 915 meters (2,000 to 3,000 ft.), where it
attains a height of about 25 meters (82 feet). Seeds were
collected by M. T. Dawe from the type locality and sent to Swingle at
the former Bureau of Plant Industry before World War I.
Under culture in the greenhouse it grew freely, but even after many
years did not flower. (See fig. 3-56.)
Balsamocitrus dawei can be propagated easily by grafting on seedlings of Aeglopsis chevalieri (which
fruits freely in the greenhouse) and twigs can be forced to root by the
so-called nurse-grafted Y-cutting method (Swingle, Robinson, and May,
1929, p. 79), where one fork of the Y is grafted on Aeglopsis until the base of the Y strikes root. It is highly probable that Balsamocitrus could be grafted also on the species of Afraegle and on Aegle
as well, as it is closely related to both of these genera.
As it is one of the largest trees among the Hard-Shelled Citroid Fruit
Trees (subtribe Balsamocitrinae), it should be tested as a stock for Aegle,
the bael fruit of India, the most important widely consumed species in
the subtribe but one that has proved difficult to grow on its own roots
in the United States.
GROUP C. THE WOOD-APPLE GROUP
This well-marked group comprises two genera, Feronia and Feroniella,
which differ from all the other genera of the subtribe Balsamocitrinae
in having a most remarkable fusion of the four to six locules of the
ovary into a single cavity (showing when young short rudiments of the
follicule lateral walls that, however, do not reach to the center of the
ovary). As the core or axis of the ovary has disappeared,
an entirely new placentation has developed in this group which is not
found elsewhere in the orange subfamily or even elsewhere in the family
Rutaceae: a placenta develops along the middle of the ventral wall of
each of the original locules and bears very numerous ovules that because
of their long raphae are pendent and spread apart until they seem to
cover the whole ventral wall.
All in all, no other group of Citrus relatives shows such striking deviation from the normal in ovary and fruit structure. Nevertheless, Citrus can be grafted on both Feronia and Feroniella,
and there can be no doubt that the genera of group C are related to
those of group B. There is less evidence of relationship of
group C to group A, but plants of both of these groups can be grafted on
Citrus.
XXXII. Feronia Corrêa31
XXXII. Feronia Corrêa, Trans. Linn. Soc. 5:224. 1800.
Type.—Feronia elephantum Corrêa = F. limonia (L.) Swing.
Distribution.—India, Ceylon, Burma, Thailand, Indo-China.
Common name.—Indian wood apple.
Flowers in loose panicles, hermaphrodite,
by abortion polygamous; calyx small, 5-toothed, caducous; petals 5,
rarely 4-6, spreading, oblong or ovate-lanceolate, imbricate in the bud;
stamens 10-12; filaments dilated, bound together by densely woolly
pubescence at the base, subulate at the apex; anthers large,
linear-oblong, attached at the base, disk short; ovary globose,
incompletely 4-6-locular, then 1-locular (with 4-6 parietal placentae),
merging into a short, thick, attenuate style; stigma oblong-fusiform;
ovules at the internal angles of the incomplete ovary walls, very
numerous, in several series; fruit large, globose, having a woody shell,
with a single cavity, with numerous parietal placentae, bearing
numerous seeds surrounded by a gum-like pulp; seeds oblong, compressed,
testa thin, brown, hairy; cotyledons thick, fleshy, radicle pointing
away from the hilum. A medium-sized spiny tree with hard
wood. Spines short, straight, axillary. Twigs
and leaves densely covered with minute pubescence when very young, soon
glabrous. Leaves deciduous (in tropical climates often
persistent), odd-pinnate, leaflets opposite, subsessile, entire or
slightly crenulate, pellucid-punctate; petiole and rachis simple or
winged.
This genus deviates widely from all the
other genera of the orange subfamily except the closely allied Feroniella
in having an ovary that in its earliest stages of development shows
four to six locules which soon fuse into a single locule with parietal
placentae with very numerous ovules. From Feroniella,
to which it is obviously closely related, it differs in having only
twice as many stamens as petals (instead of four times as many), stamens
without basal appendages, hairy seeds, and a fruit with a woody shell
not composed of wedge-shaped radial elements. The leaves of Feronia, as well as those of Feroniella,
are odd-pinnate with paired opposite leaflets on a rachis that is
composed of segments articulated at each leaf pair. This
character is found only in the tribe Citreae and there only in the
pinnate-leaved species. The fact that Citrus can be grafted on Feronia is an indication of its not too remote relationship to the True Citrus Fruit Trees.
Feronia limonia (L.) Swing. Jour. Wash. Acad. Sci. 4:328. 1914. Schinus limonia L. Sp. Pl. 1:389. 1753; Feronia elephantum Corr. Trans. Linn. Soc. 5:225. 1800; Limonia acidissima L. 1762. Illus. Roxburgh, Pl. Corom. 2:pl. 141. 1798; Beddome, Fl. Sylv. pl. 121. 1871; Wight, Icon. Pl. Ind. Or. 1:pl. 15. 1840; idem, Gartenflora 33:87. 1883, and 34:pl. 1206. 1885; Talbot, Forest Fl. Bombay Presid. 1:204. 1909; Tillson & Bamford, Amer. Jour. Bot. 25:786, figs. 47-49. 1938; fig. 3-57 this work.
Type.—Ceylon (Hermann). Herb. Brit. Mus., London.
Distribution.—India, Ceylon, Burma, Indo-China, Malay Peninsula, Indonesia.
Common name.—Indian wood apple.
This species was described by Trimen
(1893, p. 229) as follow: "A small tree, branches numerous, with smooth,
whitish bark and with sharp, straight, ascending spines, 0.5-1.5 in.
[1.2-3.8 cm] long; l. pinnate, 3-4 in. [7.5-10 cm long], rachis and
petiole flat, very narrowly winged, glabrous, lfts. opposite, in 2 or 3
pairs and usually a terminal one, nearly sessile, 1-1.5 in. [2.5-3.8 cm
long], oval or obovate, obtuse, entire, glabrous, basal ones the
largest; fl. small, numerous, in small, paniculate, sessile cymes from
the axils of fallen l., ped. slender, pubescent; cal. very small; pet.
ovate, acute, spreading, smooth; stam. 7-12, fil. very short, anth. very
large; disk finely woolly; ov. with numerous ovules in each cell, style
very short, stigma fusiform; fruit large, 2-2.5 in. [5-6.3 cm diam.],
globose, hard, pericarp woody, rough, whitish, 1-celled; seeds oblong,
compressed." He stated further: "Flowers Feb. Mar.; pale
green, stained with red purple, anthers dark red." Brandis
(1906, p. 119) stated: "Flowers dull red, generally unisexual, in lax
panicles, male and bisexual flowers frequently on the same
inflorescence." He also noted that the leaves are
deciduous. (See fig. 3-57.)
In addition to the description given
above, it should be noted that the calyx is deciduous, as Hooker (1875,
vol. 1, p. 516) pointed out: "Calyx small, flat, 5-toothed,
deciduous." He also noted that the leaves smell of aniseed
and are deciduous. According to Guillaumin (1911, pp. 685,
687), the anthers are "twice as long as the filaments."
Although apparently universally reported
as glabrous throughout except for the pedicels and peduncles, which are
pubescent, and the base of the stamens, all the specimens that Swingle
examined (from southeastern Asia, as well as greenhouse specimens from
Washington, D.C.) show minute appressed yellowish-gray or nearly
colorless hairs covering the petiole, rachis, and midribs of the very
young leaves and also of the young twigs and spines. The
very youngest new growth is covered almost as completely with these
hairs as the very young growth of Glycosmis. These
hairs soon disappear except at the joints of the rachis and base of the
petiole. The seeds are pilose, as noted by Corrêa in his
original description of the genus Feronia.
The wood-apple tree (sometimes called elephant apple), like the related bael-fruit tree (Aegle marmelos),
also native in the hill regions of northern India, is deciduous;
however, it is not reported as growing above 457 meters (1,500 feet) in
the western Himalaya, whereas the bael tree in the same region grows up
to 1,219 meters (4,000 feet). The wood apple is common in
Ceylon in dry regions but the bael tree is not native so far
south. The wood-apple tree is often planted in dooryard
gardens in southern Asia and Java.
The ability to drop its leaves puts the wood apple in a special, small group of Citrus relatives. It will be well worth while to study the wood apple and the bael fruit as examples of subtropical Citrus relatives that have acquired the deciduous habit.
As Feronia limonia can be used successfully at least for a few years as a rootstock for Citrus, it should be compared with the trifoliate orange (Poncirus trifoliata), another deciduous Citrus relative that has been used with great success as a rootstock for kumquats and for the satsuma orange. Citrus
when grafted on the wood apple is sometimes forced promptly into
bloom. Such a graft might be utilized in an attempt to force
newly originated or newly introduced varieties into bloom so that they
may be used promptly in making other desired hybrids.
The ripe fruits of the wood apple contain
a sour-sweet, aromatic pulp in which the seeds are
imbedded. This pulp is sometimes eaten mixed with palm sugar
or sweetened and stirred into coconut milk. It is also used
to make a jelly said to be more or less astringent. A
chutney is made from the pulp that is much liked by the
natives. (See De Silva, 1890, p. 722; and Watt, 1890, vol.
3, pp. 326-27.)
XXXIII. Feroniella Swingle
XXXIII. Feroniella Swingle, Bul. Soc. Bot. France 59:776. 1912.
Type species.—Feroniella oblata Swing.
Distribution.—Laos, Cambodia, North Vietnam, South Vietnam, eastern Thailand, Java.
Common name.—Feroniella.
A small tree, twigs terete, with single
axillary spines; leaves imparipinnate, with 3-6 or 7 strictly opposite
pairs of leaflets, rachis segments and petiole cylindric, or more or
less broadly winged; leaflets small (1.5-4 X 0.8-1.5 cm), obovate or
oblong, rounded or bluntly pointed at the tip; inflorescences axillary,
panicles branched from the base, flowers perfect or male by abortion,
4-6-merous (commonly 5-merous), calyx small, with 4-6 acute lobes;
petals 4-6, lanceolate or oblong-lanceolate, very acute at the tip;
stamens 16-20, filaments slender, glabrous, each furnished at the base
on the inner side with a pilose linear appendage, free above, about 2/5
or 1/3 the length of the filament, anthers oval, much shorter than the
filaments; disk very short, ovary subglobose, narrowed abruptly below
and merging abruptly above with the slender style as long or longer than
the ovary, locules at first 5 or 6 but soon confluent to 1 more or less
lobed ovarial cavity with very numerous ovules on parietal placentae;
fruits large, globose or oblate, spheroidal, with a thick, woody shell
composed of radially arranged prisms; seeds oval, flattened, testa
membranaceous, glabrous; cotyledons epigeous in germination.
Feroniella has leaves much like those of Feronia
and also similar ovaries, with a single cavity formed by the early
confluence of the original five or six locules. It differs
from Feronia in having the stamens about four times as numerous
as the petals (instead of twice as many), in having the anthers much
shorter than the filaments, in having glabrous instead of pilose seeds,
and especially in having pilose, partly free, appendages at the base of
the filaments. In this last character it differs from all
the other genera of the orange subfamily. A key to the Feroniella species is presented.
All three species of Feroniella are closely related to one another but the genus is not closely related to any genus other than Feronia.
1. Feroniella oblata Swing. Bul. Soc. Bot. France 59:779. 1912. Feroniella lucida Guill. (non Scheffer), in Lecomte, Fl. Gén. Indo-Chine 1:684. 1911. Illus. Guillaumin, loc. cit. fig. 72(1-5); Swingle, loc. sit. [sic] pl. 18; idem, in Bailey, Stand. Cycl. Hort. 3:1219, figs. 1493, 1494. 1915.
Type.—French Indo-China, Cambodia, Province of Samrong-Aong (L. Pierre, No. 652). Herb. Mus. Hist. Nat., Paris.
Distribution.—Cambodia, Laos, South Vietnam, eastern Thailand.
Common name.—Indo-China feroniella.
This species is a medium-sized spiny
tree, 8-20 m high, native in the eastern part of the Indo-Chinese
Peninsula; it is characterized mainly by the leaves with only 7-9
leaflets, which are oval-elliptic or obovate, 2-3 X 1-2 cm, rounded at
the apex or slightly emarginate, bluntly cuneate at the base, and the
cylindric, pilose petioles, 1-2.5 mm long. The rachis
segments are cylindric or narrowly winged. The flowers are
grayish-white, 1.5-2.5 cm diam.; sepals very short, 1-2 X 0.5 mm, very
pilose, soon falling; petals lanceolate, 1.2-1.8 cm long, with very
acute cuneate tips; ovary with 5-6 imperfect locules soon fusing into a
single cavity. The flattened-globose fruits, borne in
clusters of 3 or 4, are 5.5-6.5 cm wide, 4.5 cm high, and have woody
shells, 7-8 mm thick, composed of tapering prisms 1:5-3 mm diam. with
the largest end out, and arranged like the stones of a curved
arch. The center of the fruit is filled with red flesh said
to be edible.
This species, rather common in the
forests of the plains and mountains of Indo-China, makes a medium-sized
tree, up to 20 meters in height, with brilliant, deep green
foliage. The fruits look like small green
oranges. Swingle's citation of Lecomte in the synonymy above
and the illustrations cited for this species appear to be
incorrect. Guillamin [sic] (1911, fig. 72) presents an obvious illustration of Feronia lucida instead of Feroniella oblata. Since
Swingle's original notes were not available for clarification, the
synonymy is retained intact. Further study will be required
to ascertain correct synonymy for Feroniella oblata.
Plants of this species grown in the U.S.
Department of Agriculture's greenhouses in the Washington, D.C. area
were extremely spiny and had small leaves, only 6 to 12 cm long, with
numerous small leaflets and distinctly but narrowly winged
rachis. A young tree of this species was observed growing
very vigorously in Colonel Robert H. Montgomery's arboretum at Coconut
Grove, Florida, in the peculiar sandy-loam and porous-limestone soil
characteristic of the extreme southeastern section of that
state. The long, nearly straight side branches were
extremely spiny. Because of its spiny character, this
species should be tested as a hedge plant. As it is clearly
related to Feronia, a genus that forces premature blooming of Citrus grafted on it, Feroniella should also be tested as a stock for Citrus.
2. Feroniella pubescens Tan. Bul. Mus. Hist. Nat. Paris, 2 sér. 2:161. 1930.
Type.—Java (Zollinger, No. 493). Herb. Kew (Tanaka ident. No. Q-1197). Paratype: Burma (Wallich, No. 6365). Herb. Kew.
Distribution (fide Tanaka).—Java, Burma, Thailand, South Vietnam.
Common name.—Velvety feroniella.
Tanaka's original description reads as follows (in translation): "Feroniella pubescens Tanaka, n.sp. Limonia ? pubescens,
Wall. Cat. no. 6365 nom nud. Twigs spiny, spines small,
solitary or paired; recurved. Leaves odd-pinnate,
5-7-paired, rachis pubescent, more or less widely winged, leaflets opposite,
subsessile, slightly serrulate, lateral leaflets oblong, acute or
subacute, terminal one ovate, acute or acuminate.
Inflorescence axillary, paniculate, few-flowered. Calyx
5-lobed, lobes somewhat triangular, pubescent. Petals 5,
oblong, acute, puberulous. Stamens numerous, much longer
than the petals, filaments subulate, with a pilose appendage, anthers
somewhat rounded. Style linear, puberulous, stigma capitate,
5-lobed. Immature fruits small, obovate, with 5 locules,
cortex woody, of homogenous structure."
Tanaka made a specimen collected in Java
by Zollinger (No. 493, in the Kew Herbarium) the type of this species,
but he considered Wallich's No. 6365, collected in Burma at Taong-dong
in 1826 and preserved in the Kew Herbarium, as a paratype.
He provided Swingle with a photograph of the paratype.
Wallich's specimen was studied by J. D. Hooker (1875, p. 507), who found
only three to five pairs of leaflets (not five to seven, as Tanaka
stated). The lateral leaflets are 3.5 to 6 by 0.8 to 12 cm,
with the margins subentire or slightly and irregularly serrulate above
the middle but entire and cuneate below the middle; the rachis segments
are 1.2 to 2.5 cm long, with rather broad wings, 2 to 4 mm
wide. This specimen looks like a form of Hesperethusa crenulata
with the leaflets less crenullate than usual. The fruit
that Wallich associated with this number was suspected by Hooker (1875,
vol. 1, p. 508) of being "probably that of another plant."
Tanaka described an immature, 5-locular, obovate fruit with a woody
shell, of homogenous texture that does not fit well with Feroniella as
now known. However, he described flowers that have many
stamens with pilose appendages on the filaments, such as are known only
in Feroniella.
Until better material can be studied, the true character of this species must remain in doubt.
3. Feroniella lucida (Scheff.) Swing. Bul. Bot. Soc. France 59:781. 1912. Feronia lucida Scheff. 1870. Illus., Koorders & Valeton, Icon. Bogor. 2:190, pl. 149. 1904; fig. 3-58 this work.
Type.—Java, Rembang Province (Teijsmann). Herb. Hort. Bot., Buitenzorg (now Kebun Raya, Bogor, Java).
Distribution.—Central Java; in teak (Tectona grandis) forests.
Common name.—Java feroniella.
The fullest description yet made of this
species is that of Koorders and Valeton (1896, pp. 251-53); it reads in
translation as follows: "Twigs slender, gray, young tips
pubescent. Leaves 2-5- (usually 3-4-) paired; rachis
pubescent, articulate at the nodes, internodes more or less winged
above, petioles very short, pubescent. Leaflets elliptic or
obovate, obtuse at the apex, often cuneate at base, entire or
subcrenulate, margins recurved, shining and glabrous above, below opaque
pubescent all over or only at the veins, pellucid-punctate over the
whole surface, but having a single series of larger glands near the
margin. Panicles loose, made up of 3-flowered cymes, often 2
or 3 grouped in the axils, pubescent, shorter than the
leaves. Flowers large, hermaphrodite, or staminate by
abortion of the stigma and ovules (the ovary seems well developed and
grows for a time); flower-buds opening early with all [flower] parts
continuing to grow. Calyx lobes linear, pubescent,
deciduous; petals acuminate, margins reflexed at base, opening erect,
then recurving, glabrous; stamens 16-25 in mature flowers, exserted;
anthers oblong, 4-cornered, cordate at the base, truncate-mucronulate at
the apex; pollen [grain] round with 3-4 pores, with granulose exine;
ovary globose, glabrous; style in perfect flowers elongate, terete,
glabrous with an exerted persistent fusiform stigma; in the majority of
the flowers (male?) the style is very short, the stigma deformed or
aborted. Fruits with a very thick woody epicarp.
Seeds immersed in glutinous pulp arising from the placenta and the
endocarp; testa thin, woody, with a coriaceous tegment.
"Small or medium-sized trees.
Leaves 60-100 mm long, internodes 10-20 mm; leaflets 22-30 mm long,
15-22 mm wide; petiolules 1-2 mm. Petals in fully developed
flowers 12-14 mm; stamens 10-13 mm; disk villose, 2-5 mm high; anthers 3
mm. Ovary with style 13 mm. Fruit 60-70 mm
diam.; epicarp 10 mm thick."
This species is native in central Java,
usually growing at less than 400 meters altitude. It is a
medium-sized tree, 10 to 15 meters (30 to 49 feet) tall, with a straight
trunk 20 to 30 cm in diameter. It is common in stands of
teak (Tectona grandis). It sometimes occurs in
situations where the soil is periodically very dry, for example, at
Kedoengdjati in the Semarang area.
Koorders and Valeton (1896, pp. 251-53) first discovered that in this species, as in Feronia limonia, a large part of the flowers are male through partial abortion of the ovary. Feroniella lucida is called kawista krikil by the Javanese, who eat the fruit as they do that of the cultivated Indian wood apple, Feronia limonia, which is called kawista by them.
The young trees of this species (see fig. 3-58), like those of the Indo-Chinese Feroniella oblata,
have slender, straight branches armed with numerous long, slender,
sharp thorns frequently arising in pairs. It should be
tested as a hedge plant and as a stock for dwarfing Citrus.
Experiments made by the U.S. Department of Agriculture in greenhouses
in the Washington, D.C. area have shown that Citrus, although it
grows very slowly on this rootstock, may be forced into early blooming
by this stock, as it is by the related Indian wood apple, Feronia limonia. Feroniella lucida should, like F. oblata, grow well in extreme southeastern Florida.
RETROSPECT AND PROSPECT
In concluding this discussion of the
taxonomy of the orange subfamily, it may not be amiss to emphasize the
practical as well as the scientific importance of the wild relatives of
our cultivated citrus trees. Probably no other important
cultivated crop plants can boast such a significant and varied group of
wild relatives. The plants allied to Citrus show all
degrees of affinity with our cultivated oranges, lemons, and
grapefruits. Some of them are to be found in the genus Citrus;
others are in genera closely related to it; still others belong to
distantly related tribes, which may show little superficial resemblance
to Citrus.
The Citrus wild relatives exhibit a
wide range of adaptability to climatic and soil conditions.
Mention of but a few of the more outstanding examples should suffice to
substantiate this statement. Eremocitrus, of
semiarid habitat, has the ability to grow with little or no organic
nitrogen in the soil; it also withstands relatively high concentrations
of salts in the soil moisture. Severinia endures percentages of boron in the soil solution strong enough to kill Citrus; even more striking is the fact that under such conditions Severinia
roots absorb and transmit so little boron that they have supported
experimentally healthy grafts of even the highly sensitive
lemon. Other wild relatives of Citrus have acquired,
through long ages of natural selection, high resistance to the attacks
of certain insect pests or fungous diseases. A species of Citropsis, native to Republic of the Congo, is immune not only to the attacks of a beetle whose larvae burrow in the collar of Citrus trees, but also to the foot rot fungus that is made more destructive to Citrus by the injuries caused by the beetle. This Citropsis (C. gilletiana) has been found to make a good rootstock in Republic of the Congo for several cultivated species of Citrus, which grow and fruit well when grafted on it; however, it cannot be grown on any Citrus rootstock in that country.
The promising beginning that has been
made in using these wild relatives, and also hybrids derived from them,
as rootstocks for our cultivated varieties of Citrus opens up
possibilities in citrus culture well worth the attention of citrus
experts. To study and test to the best advantage these wild
relatives of Citrus, it is essential to have a thorough knowledge
of their taxonomic relationships as well as of their physiological
peculiarities and special adaptations to the climatic and soil
conditions of their native habitat. In addition to the
species of wild relatives and their hybrids that are useful as
rootstocks, there are others closely enough related to the species of Citrus to hybridize with them and yield promising new types.
The hybridization of the wild species of
True Citrus Fruit Trees with the cultivated forms has also opened a new
field of research on the origin of some of the more puzzling cultivated
varieties. The Yuzu, a hardy variety widely grown in Japan
and sparingly in northern China as a substitute for the lemon, has been
considered by some to be a good natural species of Citrus. However, it is now found to be a hybrid of a recently discovered Chinese species of Citrus (C. ichangensis) probably with a sour mandarin (C. reticulata var. austera). A hybrid of similar parentage made in the United States is astonishingly like the Yuzu.
The study of Citrus and its wild
relatives has already yielded appreciable results and it is gratifying
to know that botanical exploration is very likely to bring to light
additional new species or even new genera of Citrus relatives. The most recent general treatise describing all the genera and species in the orange subfamily except Citrus
was published in 1861 by Daniel Oliver, who recognized twelve genera
and fifty species, some of them doubtful. As late as 1896,
Adolph Engler recognized and described only fourteen genera and
estimated the number of species at seventy-one. In contrast
to this slow increase in the number of genera and species recognized
during the second half of the nineteenth century, a very rapid increase
has occurred since 1900. The present synopsis recognizes no
fewer than thirty-three genera and 203 species, of which seventeen
genera and eighty species have been described since 1900, most of them
since 1910. In addition to these eighty new species, some
fifty species named before 1900 but not well understood have been
studied anew and are now accepted as valid. In other words,
seventy-five years ago nearly two-thirds of the species recognized today
were either completely unknown or not known adequately.
Vast areas of the Monsoon region,
including the most densely populated part of the distribution area of
the orange subfamily, are still inadequately known. When
these regions and certain sections of tropical Africa are adequately
explored by competent botanical collectors we may expect new species and
even some new genera of the orange subfamily to be brought to light.
Doubtless many physiological
peculiarities, as yet undiscovered, are possessed by certain of the wild
relatives of Citrus, peculiarities that have arisen during the
several tens of million of years in which these plants have been
evolving independently and becoming more and more fully adapted to the
special environmental conditions prevailing in the areas inhabited by
the respective species. These areas extend from the
near-desert of east-central Australia through the tropical jungles of
the Monsoon region to the semiarid foothills of Northwest India and West
Pakistan; reappearing again in Africa, they extend from the mountains
and plateaus of East Africa to the dense jungles of the lower Congo and
the lands bordering the Gulf of Guinea in West Africa.
In the face of such abundant material,
citrus experts can undoubtedly solve certain important technical
problems with greater ease if the varied behavior of the numerous near
and distant Citrus relatives is seen in proper perspective.
Looking ahead, it is reasonable to expect that citrus breeders will use wild relatives of Citrus,
not only as parents for new types of disease-resistant or otherwise
superior citrus fruits and for breeding new hybrid rootstocks adapted to
special soil conditions or resistant to root diseases, but also as
research material to aid in the solution of many difficult questions in
the phylogeny of our cultivated species of Citrus.
Through experimentation and research, taxonomists, floral anatomists,
cyto-taxonomists, and chemo-taxonomists will develop better explanations
concerning the nature and relationship of citrus taxa. The
taxonomic system will be revised and improved. The truth
will be approached but it will never quite be attained because man's
knowledge concerning living organisms forever remains incomplete.
ACKNOWLEDGMENTS
The acknowledgments presented below were
made by the senior author, Walter T. Swingle, in the first edition of The Citrus Industry
(Webber and Batchelor, 1943, vol. 1, pp. 128-29). The
acknowledgments are published here without change as they originally
appeared.
1. To Mr. Benjamin Y.
Morrison, in charge of the Division of Plant Exploration and
Introduction, for putting at my disposal all the resources of his
division, both of material and apparatus and of personnel.
2. To the following persons
and institutions for the loan of herbarium specimens, photographs of
type specimens, notes, etc.: Sir Arthur W. Hill, Director of the Royal
Botanic Gardens, and Mr. H. C. Sampson, Economic Botanist, Kew, Surrey,
England; Dr, Edmund G. Baker, Department of Botany, Museum of Natural
History, South Kensington, London, England; Mr. R. E. Holttum, Director
of the Botanic Gardens, Singapore, Straits Settlements; Mr. I. Henry
Burkill, Former Director of the Botanic Gardens, Singapore, Straits
Settlements, and now working at the Royal Botanic Gardens, Kew, Surrey,
England; Professor J. R. Matthews, Regius Professor of Botany and
Curator of the Garden, University of Aberdeen, Aberdeen, Scotland; Dr.
H. J. Lam, Director of the Rijks Herbarium, and Dr. S. J. van
Oosterstroom, First Assistant, Leiden, Holland; Professor W. Robyns,
Director of the National Botanic Garden, Brussels, Belgium; Professor N.
E. Svedelius, Director of the Botanical Institute, and Dr. Carl G. Alm,
keeper of the Hortus Linnaeanus, University of Uppsala, Sweden;
Professor Dr. L. Diels, Director of the Botanical Gardens and Botanical
Museum, and Dr. M. Domke, Associate Curator of the Herbarium,
Berlin-Dahlem, Germany; Professor Henri Humbert, Director of the
Laboratory of Botany (Phanerogams), Museum of Natural History, Paris,
France; Professor Cyril T. White, Government Botanist of Queensland, and
Director of the Botanic Garden, Brisbane, Australia; Professor
Tyôzaburô Tanaka, Director of the Horticultural Institute, Taihoku
Imperial University, Taihoku, Formosa, Japan; Dr. Eduardo Quisumbing,
Curator of the Herbarium, Bureau of Science, Manila, P.I.; Mr. K.
Biswas, Director of the Royal Botanic Garden, Calcutta, India; Dr. Elmer
D. Merrill, Arnold Professor of Botany, Administrator of the Botanical
Collections of Harvard University, and Director of the Arnold Arboretum,
Jamaica Plain, Massachusetts; Dr. Herbert L. Mason, Associate Curator
of the Herbarium, University of California, Berkeley, California; Dr. H.
A. Gleason, Curator of the Herbarium, and Dr. A. C. Smith, Associate
Curator, New York Botanical Garden, Bronx Park, New York City; Dr.
William R. Maxon, Curator of the U. S. National Herbarium, U. S.
National Museum, Washington, D.C.
3. To Dr. Albert H. Tillson,
Junior Botanist, Bureau of Plant Industry, Plant Introduction Garden,
Glenn Dale, Maryland, for efficient cooperation in using and improving
the Juel method of restoring herbarium specimens of flowers, fruits,
etc., and making serial microtome specimens of them.
4. To my wife, Maude
Kellerman Swingle, who aided me for several years in the preparation of
this chapter and who is joint author with me of all the taxonomic names
used in the genus Citropsis.
FOOTNOTES
1. The Monsoon region is used here in a broad sense to include southeastern Asia, the East Indian Archipelago, New Guinea, Melanasia, northeastern Australia, and New Caledonia.
2. The specific name excavata was no doubt employed by Burmann because of the hollowed out shape of the base of the filaments.
3. C. Lauterbach (1918, p. 221) gives the Aurantioideae as having an altitudinal limit of about 300 meters in New Guinea, but reports that several genera of the Toddalioideae and Xanthoxyleae are found growing in cloud and fog belts of the mountains at 800 to 1,500 meters altitude and that three species of Acronychia occur at altitudes of from 2,700 to 3,300 meters.
4. These protuberances when restored nearly to their original dimensions by soaking in hot water and dilute ammonia water are 0.9 to 1.2 mm in diameter. Serial microtome sections show a central woody cylinder 0.5 to 0.6 mm in diameter, with pith in the center and numerous (about 120 to 130) radial rows of thick-walled wood parenchyma cells (4 to 8 rows deep) that are separated from the larger thinner-walled cells of the peripheral tissues by very thin-walled cambium-like cells. On the inner boundary of the woody cylinder next to the pith are found eight groups (each of 4 to 10 cells) of wood vessels with still thicker, pitted walls. The epidermal cells are unusually large; no oil glands were seen. Longitudinal sections showed cells longer (some very much larger) than broad and almost all with cross walls running at right angles.
5. The Latin name of this species was, by some accident, omitted from the original description published in Nos. 4 and 5, October 1, 1911, and December 20, 1911, and did not appear until more than two years later in No. 12 (in the index on p. 390 and in the "Errata et Corrigenda" on p. 406), published on December 31, 1913.
6. The first publication by Wallich of Buchanan-Hamilton's generic name was in the form Lavanga, as nearly as can be deciphered from the minute lithographed manuscript writing. This was apparently a mistake, as the vernacular name is derived, according to Roxburgh (1832, vol. 2, p. 380), from the Sanskrit name luvunga-luta (called a Bengali name by Voigt, 1845, p. 140).
7. H. H. Hume was the first citrus expert to utilize pulp-vesicles as an important means of distinguishing the commonly cultivated species of Citrus Fruit Trees. He states (1909, p. 14; also 1926): "It is believed that the juice sacks of the pulp, their size, shape and appearance in the cut surface of the fruit, can be used to some extent as a diagnostic feature in classification, a point which seems to have been quite generally overlooked." Hume figured the pulp-vesicles and used them in his technical descriptions of the eight species of Citrus, Fortunella, and Poncirus that he recognized.
8. Roemer was apparently the first to notice that the Limonia monophylla of Loureiro (1790, p. 271), wrongly credited by Loureiro to Linnaeus, was not that species but the very different plant, Severinia buxifolia, which Roemer renamed in Loureiro's honor.
9. Tanaka repeated Loureiro's error and wrongly identified Limonia monophylla L. with Severinia buxifolia because he found poor specimens of this latter species labeled Limonia monophylla in the herbarium of Linnaeus, preserved by the Linnean Society of London. However, B. Dayton Jackson, for many years the keeper of the Linnean Herbarium, had already indicated categorically (1912, pp. 26 and 27) that of the material in the Linnean Herbarium labeled Limonia monophylla (including the specimens seen by Tanaka) "there is no specimen so named by Linné," a verdict confirmed by Airy-Shaw (1939, p. 292).
10. This name is given by Groff (1923, p. 273) in his list of some 7,600 Chinese plant names used in Kwangtung Province, China. The Chinese characters used to write this name are given by Eitel and Genähr (1911, characters Nos. 6871, 5047, and 3286), with the tones accurately marked.
11. A curious plant was described under the name Lamiofrutex by C. Lauterbach (Nova Guinea 14:147 [1924]) as a Rutaceae of doubtful position because no fruits were known. This plant is very distinct from any other genus of the Aurantioideae because (1) the ovules (single in the unilocular ovary) are erect; (2) the leaves have very few lateral veins, have wavy margins, are decurrent at the base, and are somewhat shining below; (3) the stems are very slender, creeping and rooting, sparingly branched; and (4) its habitat is in the fog forest at 1,420 to 1,450 m altitude.
The authors have omitted it from the Aurantioideae, although it was included by Engler (1931, p. 330) immediately after Atalantia (used by him in a broad sense) in his last treatise on the Rutaceae. A photograph of the type specimen, kindly sent Swingle by the Director of the Botanical Museum at Berlin-Dahlem, shows leaves very different from those of any species known in the orange subfamily.
12. Made from herbarium materials by the modified Juel method.
13. Ripe fruits of H. crenulata that Swingle picked on May 30, 1939, from a tree growing at the Horticultural Experiment Station at Deodoro near Rio de Janeiro (a plant which Swingle had sent to Brazil through Snr. Felisberto de Camargo about ten years before), were very bitter, not sour. Probably the oft-recurring statement that the fruits of this species are "very acid" stems from the general but improper attribution to it of the name Limonia acidissime L., a name originally applied by Linnaeus to a very different plant, the wood apple, here called Feronia limonia (see. p. 416), the fruit of which is said to have "a strong acid-sweet taste" and to make excellent jelly.
14. Some of the species of Atalantia, such as A. ceylanica, have fruits with very few pulp-vesicles, apparently because the seeds have become very large and fill the locules of the fruit almost completely, leaving little room for pulp-vesicles. These species constitute the subgenus Rissoa. Another species, A. guillaumini, which has much resemblance to A. ceylanica, seems to have no pulp-vesicles; it has perhaps lost them by retrograde evolution.
15. Usually credited to Wight and Arnott but first published by Wight in January, 1834, with full description and plate, whereas the Prodromus in which it appears as A. racemosa Wt. et Arn. was not published until after March 20, 1834, and furthermore gives only a very brief description scarcely adequate for valid publication.
16. Harry H. Hazelwood, a prominent nurseryman of Epping, New South Wales, reported to Swingle in a letter dated January 23, 1924, that at Carwell Station (Long. 14°7 48' E., Lat. 31° 15' S.), 44 miles southwest of Coonamble, there had been a drought of some months' duration during which a number of trees of the Buddah, Eremophila mitchelli, had died, but that in the large tract covered with a growth of Eremocitrus glauca "not a single instance was noted of these trees dying of drought." O. E. Friend, a resident of Carwell, wrote on November 16, 1915, that the rainfall for the preceding 12 months had been only 9.09 inches and for the year before only 14.80 inches, yet "the trees [of Eremocitrus glauca] were wonderfully green at present in spite of the prolonged droughts." The rainfall at Carwell averages about 19 inches, according to Mr. Friend.
The drought resistance of Eremocitrus glauca was discussed by Flanders (1932), who reported seeing small trees growing at Mootwingee (Long. 142° E.), where the annual rainfall averages about 12 inches. He also told Swingle of seeing living but leafless trees near Longreach, Queensland (Long. 144° E.), where no rain had fallen during the preceding 15 months and no green vegetation could be seen!
17. Tanaka, in his original description and in his later notes (1931b, p. 12) on this plant, reported this species as native to New Guinea. He was evidently in error, as the type specimen only (Peekel, No. 408) is cited, and it was collected in New Ireland, some 600 kilometers northeast of the nearest shore of New Guinea.
18. P. Brough (1933, p. 68) cited W. N. Benson (1923, pp. 1-62) in support of his view that "Australia is considered to have been joined to the Asiatic mainland at least during the Cretaceous period, but probably a complete separation has existed since the beginning of the Eocene." The migrations of higher plants into Australia are held to have occurred during later Cretaceous times.
19. Before its hybrid nature had been established, this form was called, both in the Agricultural Research Service greenhouses at Washington and in the field tests, Microcitrus virgata, a provisional name alluding to its very numerous slender, straight, whiplike twigs. This provisional name was never validated by proper publication, but is sometimes seen in print as, for example, in Fawcett (1936, p. 177).
20. The fifteen "primary elements" of the genera Citrus, Poncirus, and Fortunella given by Tanaka (1935b) are as follows: (1) Citrus macroptera Mont., (2) C. hystrix DC., (3) C. aurantifolia Swingle, (4) C. medica Linn., (5) C. limon Burm. f., (6) C. limonia Osbeck, (7) C. grandis Osbeck, (8) C. aurantium Linn., (9) C. sinensis Osbeck, (10) C. junos Sieb. ex Tanaka, (11) C. ichangensis Swingle, (12) C. tachibana Tanaka, (13) C. depressa Hayata, (14) Poncirus trifoliata Raf., (15) Fortunella japonica Swingle.
21. Tanaka's translation.
22. All species are in fact compatible.
23. There are a number of so-called species of citrus fruit trees that are of doubtful status. They may be natural species of comparatively recent origin, not yet far removed from their ancestral forms, or they may be chance hybrids or sports that have been propagated by man or may even be propagated spontaneously by apogamic embryos that reproduce the hybrid or sport exactly. The term "satellite species" is here used to designate species of doubtful validity that may prove to be one of such forms.
24. As noted, naringin is found in the pummelo (C. grandis) and in the grapefruit (C. paradisi), a satellite species; see also table 3-4.
25. M. B. Matlack (1931, p. 438), in studying the plastids or chromoplasts in the pulp-vesicles of citrus fruits, found that "their size and shape appear to be characteristic of the species from which they are obtained…the tangerine, Satsuma [his fig. 4] and willow-leaved mandarin oranges have spindle-shaped plastids…in the King orange they are isodiametric [his fig. 3]." Such isodiametric chromoplasts occur, according to Matlack, in "the numerous varieties of the sweet orange." In other words, the King orange representing very nearly the type of C. nobilis (as originally published by Loureiro), has chromoplasts similar to those of the the [sic] sweet orange, C. sinensis, and very different from those of the loose-skinned orange, C. reticulata. This is additional proof that it is a hybrid of the sweet orange and the loose-skinned orange.
26. Hall (1938) found in the leaves and in a thin layer of the peel (just between the yellow outer peel and the albedo) a new enzyme of the glycosidase type, able to hydrolize naringin in vitro at low temperatures (37° C.) at pH 7 into "an insoluble aglycone, naranginin (or naringetol)" and a new disaccharide sugar, distinct from rutinose.
27. Unfortunately, the original description covered fruits of the so-called Ichang lemon collected by E. H. Wilson in Hupeh Province. At that time they were believed to be from a cultivated form of C. ichangensis. Seeds of these fruits were introduced into the United States about 1914; trees grown from them have leaves entirely different from the true Ichang papeda. The so-called Ichang lemon is probably a hybrid of C. ichangensis with a species of subgenus Citrus.
28. The moli kana, or edible moli, of the natives, correctly classed by Seemann (1862, p. 321) as C. decumana (= C. grandis).
29. Merrillia, which bears a large fruit with a tough, leathery shell somewhat analogous to that of Swinglea and with seeds covered with flattened hairs (paleae) somewhat resembling the seeds of Swinglea, would seem, at first sight, to belong to this group, but in its habit of growth and in its leaves (with alternate leaflets) and wood it shows close similarity to Murraya paniculata. Swingle followed Engler (1931, p. 211), a lifelong student of the Rutaceae, in removing Merrillia from the subtribe Balsamocitrinae, to which he at first assigned it, and placing it in the tribe Clauseneae next to Murraya.
There are also certain similarities to be seen between Swinglea and Burkillanthus, but the fruit structure of the latter is clearly very different.
30. This unusual number of stamens is almost certainly due to the outer whorl (alternative with the petals) persisting in the ancestral number, whereas the inner whorl is doubled at an early stage of development. Penzig, who held to the view of obdiplostemony in Citrus was hard pressed to find clear proof of any differentiation of the stamens of Citrus into two distinct whorls. He finally discovered (1887, p. 69) a not uncommon monstrosity, a partly double-flowered variety of Citrus in which the stamens of the outer whorl but not the inner whorl were transformed into petals. The flower of A. gabonensis is the first instance yet found in the orange subfamily of a normal (not teratological) difference in the stamens of the two whorls.
31. Airy-Shaw (1939, p. 293) has proposed substituting the generic name Limonia for Feronia. However, in view of the origin and subsequent misuse of the name Limonia such a substitution seems inadvisable. When Linnaeus established the genus Limonia in 1762 he failed to describe it, and although it apparently covered what he assumed to be a single species, Limonia acidissima, he included in the synonomy plants belonging to at least two species, one each, in the genera Hesperethusa and Feronia (citing illustrations of both) and probably to a third species in the genus Citrus! Thus, from the very start, the name Limonia was a nomen confusum, "derived from two or more entirely discordant elements," which "must be rejected" in accordance with Article 70 of the International Code of Botanical Nomenclature (Lanjouw, 1961, p. 50). Furthermore, the name Limonia acidissima was apparently never used by any botanist for the wood apple, but was often misapplied to the plant now known as Hesperethusa crenulata. In 1800 Corrêa da Serra established the genus Feronia for the wood apple, and since that date all botanists have so used it. On the other hand, Limonia has become a true nomen ambiguum, "permanent source of confusion or error," as it has been applied to plants belonging to at least thirteen very diverse genera, namely, Micromelum, Glycosmis, Murraya, Triphasia, Pamburus, Luvunga, Paramignya, Severinia, Pleiospermium, Hesperethusa, Citropsis, Atalantia, and Swinglea, representing both tribes and five of the six subtribes which constitute the subfamily Aurantioideae! In view of the dubious origin and wholesale misuse of the name Limonia the genus name Feronia should be conserved and Limonia should be rejected. For this reason we are using the name Feronia.