A synopsis of the tribe Desmodieae ( Fabaceae ) in southern Africa

The tribe Desmodieae has a pantropical distribution and is one of the most advanced tribes in the subfamily Papilionoi­ deae. Its greatest centres of development are in tropical Asia and America. Africa is relatively poorly endowed and only four genera comprising 16 species occur in the flora of southern Africa. Many of these species are widespread in the Old World tropics and the few African endemics appear to be closely related to them. A synopsis of the genera Desmodium, Pseudarthria, Alysicarpus and Lespedeza is given for southern Africa.


INTRODUCTION
The tribe Desmodieae comprises 27 genera with a mainly tropical distribution and is distinguished from the other tribes with jointed indehiscent fruits by the pre sence of (1-) 3-foIiolate leaves with stipels (Ohashi 1971a).
Three subtribes have been recognized in the latest treatment of Ohashi, Polhill & Schubert (1981).The largest and most polymorphic o f these is the subtribe Desmodiinae which is represented in southern Africa by three genera, Desmodium, Pseudarthria and Alysicar pus.The much smaller subtribe Lespedezinae is only represented in the flora by the naturalized bush-clover genus, Lespedeza.The type genus, Desmodium, is the most widespread genus in the tribe and with about 300 species (Ohashi et al. 1981) is also the most numerous.It occurs widely in the tropical and subtropical regions of America, Asia, Australia and Africa with two major centres of diversification: firstly, in Mexico and Brazil, where there is perhaps the largest number o f species with the most diverse development of plant parts (Schubert 1963); and then in Asia (the Sino-Indian region down through Malesia to Australia) where there are large numbers of species in many subgeneric groups.In addi tion the least specialized subgenera and the most archaic genera in the tribe are found in the Asian region, indicat ing a possible centre of origin for the genus (Ohashi et al. 1981).
O f the ten species o f Desmodium found in southern Africa most have an Asian origin, although there are a few that are endemic in Africa.Some too, are natural ized introductions from the New World.Pseudarthria with 4 to 6 species and Alysicarpus with 25 to 30 species are in the main, tropical Old World genera.These are represented in the flora of southern Africa by one and four species respectively.Southern Africa contains the tail-end of the tribe's tropical African distribution as well as a number of naturalized introductions.All specimens examined are listed alphabetically according to the name of the collector after the references at the end of the article.
The Desmodieae is a tribe of annual herbs or, more commonly, perennial suffrutices occupying, in southern Africa, the southerly extension of the large Sudano-Zambezian region of savanna and woodland areas of tropical Africa, and to a lesser extent the Afromontane and Indian Ocean coastal belt vegetation types of W erger (1978).In general the tribe occurs in the warmer and wetter parts of the Flora area.
It was recognized that several different genera existed in Hedysarum and in 1803 Michaux described the genus Lespedeza.Don transferred Anthyllus cuneata Du Mont. to this genus in 1832.In 1813 Desvaux described Des modium and Alysicarpus and in 1825, A. P. de Candolle placed all the above-mentioned species, with the excep tion of H. barbatum, into one or other of these genera.
The subgeneric treatment of Desmodium is as yet unsatisfactory but for the purposes of this synopsis the treatment of Ohashi (1973) is followed, i.e.D. repundum is placed in subgenus Podocurpium; D. setigerum, D. udscendens, D. burbatum and D. dregeunum in sub genus Nicolsoniu and the rest in subgenus Heterolomu.

Notes
(1) Desmodium repandum is found in shaded areas in moist to dry evergreen mountain, riverine or other gal lery forest often near paths or along streams, from ± 3 000 m to near sea level.It occurs as a forest floor herb or scrambling subshrub.Flowering is from August to June although most commonly from January to May.
(2) In the latest Asian revision of Desmodium by Oha shi (1973), D. repandum is placed in the most advanced subgenus Podocarpium, because it is characterized by a monadelphous androecium and long-stipitate pods con sisting of indehiscent, approximately obtriangular articles.However, the androecium cannot be considered to be truly monadelphous, the vexillary stamen being coherent (not fused) for part of its length only.The pol len grains are also quite distinct from those of all other species of the subgenus Podocarpium, especially in the shape of the grains, the colpi and thickness of the exine (Ohashi 1973).D. repandum is also noted (Ohashi 1973) for having several characters in common with some members of the less derived subgenus Dollinera.
From observations on the degree of contraction of the pseudoraceme in D. repandum it appears that this also shows a less derived situation.Occasionally one pedicel may be seen to branch off another, above the fascicle, indicating incomplete reduction of the botrys.A number of pedicels also occur in the fascicle, three or four of which may flower with one or two reduced buds in between.The fascicle in all the other species in the Flora area has been reduced to two pedicels with or without one enclosed median bud.428 (1913); Schubert: 184 (1954): Hepper: 584 (1958); Schubert: 456   (1971

Notes
(1) D. incanum is a spreading herb to woody subshrub up to 1 m (if protected from fire); the leaf shape may vary; leaves in deep shade may superficially resemble those of D. adscendens.Confusion between the two may occur on forest margins but the partially connate sti pules, deep mauve flowers and characteristic fruit of D. incanum will help to distinguish them.D. incanum is otherwise readily recognized by its shiny dark green leaves with a light discolouration along the midrib.Flowering occurs from September to June.
(2) The plant is a weed in disturbed grassland, wood land and forest edges, along streams, paths and roadsides and often occurs in lawns.It is also invasive in undis turbed grassland.
(3) D. incanum is tropical American in origin but is widely scattered throughout tropical Africa where it is introduced.It is most likely to have entered the Flora area along the Natal coast.The Zulu name 'isinama' describes the fruit which readily catches and sticks to clothing.Allen & Allen (1981) refer to the plant as Kaimi clover or creeping beggarweed and it is favoured as a forage legume in Hawaii and Florida for its tolerance to acid soils and wet warm climate.

Notes
(1) The epithets gangeticum and maculatum were published on the same date and they were combined under the name Desmodium gangeticum by Wight & A m .: 2 2 5 -2 2 6 (1834).
(2) The plant is a spreading suffrutex to erect subshrub occurring in wooded grassland, bushveld or thicket or in open grassland.It readily becomes a weed in semi-disturbed areas i.e. old lands or roadsides, and flowers from August to March.
(3) This species is widespread throughout the Old World tropics and has been introduced into America.Allen & Allen (1981) note that D. gangeticum is used as a pioneer plant to control erosion of denuded areas.The roots of D. gangeticum yield a Iectone and seven alka loids.One of these, hordenine, has been used in experi mental medicine as a sympathomimetic and another, bufotenine, is an hallucinogen.Distribution: D. setigerum occurs in the Transvaal from the Soutpansberg and Tzaneen in the north, through the area between Lydenburg and Sabie to western Swazi land in the south.In Natal it is found from sea level to 2 000 m, except in the lowveld of Zululand, and it extends to coastal Transkei.It is widespread throughout tropical Africa.

Note
The plant is a straggling herb or undershrub of shaded mesic forest floors, and flowers from November to March.On forest margins along the coast, this species may be confused with the shade form of D. incanum (see under that species).Schubert (1971) records that D. adscendens is an excellent food for stock.

Note
The plant is an erect or straggling herb in open grass land most often in moist or marshy areas in sandy soils.It can become a woody subshrub to 1 m high if protected from fire and it is common in semi-disturbed grasslands, roadsides or forest margins.Flowering may occur throughout the year.

Note
The plant is a spreading suffrutex to erect subshrub up to 1 m high, in the grassland component of open wood land, and it flowers from February to June.

Notes
(1) The plant is erect with silvery-white or fulvous stems which are appressed silky-pilose.The leaves are almost all 1-foliolate with the leaflets densely silverysilky beneath.It occurs in woodland or grassland from 1 0 0 0 -2 000 m.
(2) Schubert (1971) notes that, although this variety is quite distinguishable from var. dimorphum in the ex treme, there are many plants which form a transition between the two.
Desmodium uncinatum and D. intortum or Silverleaf and Greenleaf Desmodium, have been deliberately intro duced from central America and cultivated as pasture legumes in the eastern Cape.This is largely out of the natural range of the genus in southern Africa, and there is no evidence that they have become naturalized.D es modium asperum was once collected on the south coast of Natal but it has not been seen again.A large number of other species of Desmodium are being tested in agri cultural stations around the country for their pasture potential.Alysicarpus gets its name from the Greek, 'halysis', meaning chain and 'karpos' meaning fruit; the pods are moniliform with the joints in chain formation.

Note
Alysicarpus Neck.: 15 (1790) is not to be treated as a generic name, according to ICBN Art. 20, unless it has been published, as such, by a subsequent author.Noted in Stafleu (1976) is the following: 'Since Necker desig nated this category as 'species', the monomial names (which are in many cases the generic names of previous authors) are to be regarded as unitary designations of species and hence to be regarded as not validly pub lished'.

Notes
(1) The plant occurs as a semi-prostrate or decumbent trailing herb in the herbaceous vegetation of open areas in bushveld or in grassland up to 800 m.More com monly it becomes a weed of disturbed sandy or rocky soils in these areas, i.e. in alluvia, old lands or along roadsides.It flowers nearly all year round from July to May.
(2) A. vaginalis has been introduced into America where it is reported to have no economic importance except as a noxious weed (Schubert 1980).In Africa, however, Schubert (1980) notes that various species in cluding A. vaginalis are used locally as, 'fodder, for all kinds of domestic stock, used fresh, but preferably cut after fruiting and stored as hay'.It is also regarded as an excellent fodder for horses, but it is said to cause mucous diarrhoea if given in excess in the young and immature state during the rains.It is also known as Alyce clover, and Allen & Allen (1981) state that it is considered as a good cover crop in Malaysia to prevent erosion on clay soils o f rubber plantations.

Notes
(1) The plant is an erect to spreading herb of open areas in bushveld or in grassland in sandy, rocky or gravel soils, and often occurs in grazed, seasonally burned grassland, along roadsides or railway lines and in old lands.It flowers from October through to April.
(2) Watt & Breyer-Brandwijk (1962) report that A. zeyheri is used as a remedy in South Africa for impo tence, while Allen & Allen (1981) quote a reference in which the species has been used as a snake-bite remedy in some African communities.

Hedysarum rugosum
Distribution: the typical subspecies is recorded in the Flora area only from the Grootfontein District in South West Africa/Namibia.A specimen, Liebenberg 2789 (PRE), from Barberton in the Transvaal may also be subsp.rugosus, but it is too underdeveloped to be identi fied with certainty.Subsp.rugosus is an erect annual in open areas in thomveld savanna or in swamps.Verdcourt (1971) mentions that intermediates occur between the two subspecies in the Flora o f tropical east Africa.He notes that a few examples have been found in the Transvaal.

Notes
(1) Only the typical taxon is found in the Flora area.
(2) This species occurs as an erect annual herb of open places in bushveld or in grassland, and is often asso ciated with moisture, i.e, floodplains, depressions, saline marshes or near streams.It is also a weed of old lands or along roadsides.Flowering occurs from November to June.
(3) Allen & Allen (1981) report that this is also known as Alyce clover and, like A. vaginalis, is said to be cultivated as a summer graze for domestic animals.Watt & Breyer-Brandwijk (1962) state that A. glumaceus is used in east Africa as a remedy for thrush and veld sores.In Arabia and India the herb is used as an external appli cation to swollen feet.
The name Lespedeza is derived from Vincento Manuel de Cespedes, governor of the Florida Colony from 1 784-1790 and patron of the botanist Michaux.The current spelling of the genus name presumably resulted from illegibility or a printer's error (Allen & Allen 1981).

Notes
(1) The plant occurs in old lands, along roadsides or old railway lines.It is an herbaceous suffrutex to 0,8 m high, flowering from February to April.
(2) L. cuneata is native to eastern Asia but is widely cultivated in the United States.Known as Japanese bushclover, it is the most widespread and familiar of all the species and is used extensively to control erosion on roadside banks and similar areas (Wilbur 1963).It is also held in high esteem as a forage, hay and protein supple ment to stockfeed (Allen & Allen 1981).
Specimens are listed alphabetically according to the name of the collector for each genus.Figures in brackets after the collector's number refer to the number o f the taxon in the text.G 4 9 1 74  (1 ) NBG ; in N B G 4 9 1 7 2 ( 1 ) NBG ; in P R E 5 5 6 4 5 ( 1

S A G P /S A
the species P. hookeri by Wight & Amott in 1834.Ben tham. in his review of the Leguminosae in 1852, placed Hedysarum barbutum and Nicolsoniu caffru under Des modium, calling the latter Desmodium dregeunum.Har vey (1862), in revising the South African representatives of the tribe for Floru cupensis, placed Nicolsoniu setigeru under Desmodium and described a new species, Alysicarpus zeyheri.The genus Nicolsoniu was later put into synonomy with Desmodium.

Hedysarum adscendens Swartz: 106 (1788) reprint 1962; Swartz: 1263(1806).
has led to confusion between two separate species, Desmodium setigerum (E.M ey.) Benth.exHarv.andD. hirtum Guill.&Perr.This began with D. hirtum sensu Bak.: 163(1871).(2)The plant is a prostrate or low semi-erect suffrutex of open grassland in damp sites, occurring occasionally on streambanks, forest margins or on drier rocky hill sides.It is also found in semi-disturbed vegetation on roadsides and flowers from December to May, i.e. it is a later summer-flowering species.Ghesquiere 4994 (BR, holo.).Distribution: D. adscendens var.robustum is found in the Soutpansberg and Woodbush areas of the northern Transvaal and entering from Mozambique along the Natal coast to the Transkei border.It is widespread in tropical Africa but the species is pantropical, from America, Africa, Asia and Malesia.

Du Plessis 1136 (PRE. PRU); Galpin 1158 (GRA. NH. PRE. SAM); Leendert: 399 (BOL, J. PRE): Rudatis 131 (STE); Stexn 995 (NBG).
A. zeyheri occurs in the Transvaal and northern Natal at altitudes between 9 0 0 -2 400 m.It is found from Pietersburg southwards to Pretoria, and from Pretoria westwards to Zeerust in Sourish Mixed Bush veld.East of Pretoria it occurs in the North-eastern Mountain Sourveld and Lowveld Sour Bushveld from Lydenburg, Nelspruit and Barberton down through Swa ziland.It also occurs in the North-eastern Sandy Highveld, Piet Retief Sourveld and related veld types from near Middelburg through Ermelo to Louwsburg and Mahlabatini in the south.