Erythrineae ( Fabaceae ) in southern Africa

Erythrineae ....................................................................... ..1 Key to indigenous genera ........................................... ..2 Erythrina ........................................................................... ..2 Pollination and floral morphology ............................ ..3 Economic uses .............................................................. ..3 Key to the subgenera of Erythrina (world-wide) ... 3 Synonymy of all subgenera and sections represented in southern Africa ...................................................3 Key to the indigenous subgenera and sections ........4 Key to indigenous species ............................................4 1. E. abyssinica ......................................................... ..4 2. E. latissima ..............................................................5 3. E. decora ................................................................. .7 4. E. mendesii ..............................................................7 5. E. lysistemon ........................................................... .7 6. E. caffra .................................................................. .9 7. E. humeana ..............................................................9 8. E. zeyheri ................................................................. .10 9. E. acanthocarpa ..................................................... .11 Natural hybrids ..............................................................11 10. E. x coddii ........................................................... .11 11. E. x johnsoniae .....................................................12 12. E. x dyeri ..............................................................12 13. E. x hennessvae .................................................. .12 Exotic species of Erythrina common in cultivation in southern Africa ..................................................12 Synoptic key to exotic species ..................................12 Section Duchassaignia ............................................... .13 14. E. fusca .................................................................13 Section Cristae-galli .................................................. .13 15. E. crista-galli ........................................................13 16. E. falcata .............................................................. .14 Section Micropteryx .....................................................14 17. E. poeppigiana .....................................................14 Section Macrocymbium ...............................................14 18. E. senegalensis .....................................................14 19. E. livingstoniana ..................................................14 Section Stenotropis ..................................................... .15 20. E. speciosa ...........................................................15

A genus of more than 100 species distributed through out the tropics and subtropics.Nine indigenous species occur in the FSA region of which E. decora and E. acanthocarpa are endemic while a third, E. caffra, may also be endemic.Four natural hybrid taxa occur in the area, one of which is ± fully fertile (E.x dyeri) and the other three ± sterile.
The generic name Erythrina is derived from the Greek erythros, meaning red, in allusion to the colour of the vexillum and of the seed of most species.
Within the genus 5 subgenera have been recognised (Krukoff & Barneby 1974) with 26 (25) sections.I am unable to uphold K rukoffs (I.e.) separation of sections Erythrina and Corallodendra which, in my opinion, intergrade.Because of this separation of these two sec tions, Krukoff (I.e.) found it necessary to set aside the original generitype, E. corallodendrum L. (which he proposed as the type of section Corallodendra Krukoff) and substitute E. herbacea L. as lectogeneritype.If section Corallodendra Krukoff is sunk in section Erythrina, as I propose, the generitype remains E. corallodendrum L. All five subgenera are represented on the African con tinent, but only two have indigenous representatives in southern Africa.Because several exotic species of Erythrina are in cultivation in southern Africa, with a strong likelihood of more being successfully introduced, a synoptic key (p.3) to all the subgenera is provided, together with synoptic keys to the indigenous (p.4) and the most commonly cultivated exotic species (p.12).

PO LLINATION A N D FL O R A L M ORPHOLOGY
Pollination in Erythrina, a predominantly red-flowered genus, is effected principally by birds.Southern African and all other Old World species are pollinated by passerine (perching) birds, whereas among New World species, some are passerine bird-pollinated and others are hummingbird-pollinated.
Passerine bird-pollinated species are characterised by having the inflorescence axis usually held horizontally in arborescent species, by inward-facing, ± gaping flowers, by a copious supply of hexose-rich nectar (Baker & Baker 1983) and by poHen grains somewhat sticky, varied in size and ornamentation between species, almost invariably with either small lumina or with sexinous granules present (Hemsley & Ferguson 1985).
Hummingbird-pollinated species differ in having the inflorescence axis vertical, the horizontally held, outwardfacing flowers 'tubular', smaller quantities of nectar with a higher sucrose:hexose ratio (Baker & Baker I.e.) and dry, powdery, medium-sized pollen grains with a simple, regular, reticulate ornamentation and no sexinous granules in the lumina (Hemsley & Ferguson I.e.).
Inflorescence, flower and pollen morphology of the arborescent species, E. lysistemon, E. caffra (subgenus Erythrina), E. latissima and E. decora (subgenus Chiroca lyx) is typical of passerine bird-pollinated species w ith the peduncle providing a perch and the essential whorls of the flower directed towards the proximal end of the peduncle, i.e. inward-facing towards the perch.The flowers of E. lysistemon gape less widely than those of the other three species.The inflorescence attitude of E. abyssinica (subgenus Chirocalyx) is unusual in that the axis is vertical.
Inflorescence attitude of the four non-arborescent species, E. humeana, E. zeyheri, E. acanthocarpa (sub genus Erythrina) and E. mendesii (subgenus Chirocalyx) differs from that of the arborescent species in that the flower-bearing part of the rhachis is erect.The inflores cence axis of E. humeana, E. zeyheri and E. mendesii elongates markedly as flowering progresses.The proximal part of the axis in taller specimens of E. humeana (a shrub) is often horizontal with the distal part remaining vertical.Erect, progressively elongating inflorescences in lowgrowing species probably serve to keep the flowers visible and accessible to pollinators above the level of the surrounding vegetation.
Although birds do not appear to discriminate between species (Jacot Guillarmod et al. 1979), any one plant being visited by a number of local bird species, it may be significant that sunbirds (which have finer feathers at microscopic level than other passerine birds, particularly on the feathers of the patches of iridescent plumage on the throat and head of the males), are the main pollinating agents of E. humeana and E. zeyheri.(The pollinators of E. acanthocarpa and E. mendesii are not known.)New World hummingbirds alone have similar plumage.Possession of long, often curved beaks is another feature shared by the unrelated African sunbirds and American hummingbirds.Hemsley & Ferguson (I.e.) noted that pollen of E. humeana and some pollen of E. zeyheri is morphologically similar to "hummingbird-type' pollen.The erect inflorescences and deflexed, 'tubular' flowers of section Humeanae they consider to be adaptations for pollination by sunbirds.which, like hummingbirds, carry pollen on their beak and on the specialized head and throat feathers, whereas other passerine birds carry pollen on the coarser chest feathers.

EC O N O M IC U SES
Apart from the use of Erythrina spp. as ornamental plants and as shade plants, little commercial value has, until recently, been attached to the genus.Various parts of the plants have, however, long been used as ingredients in tribal medicine and magic.Phytochemical analyses have shown that as well as several poisonous alkaloids the seeds contain a protein which simplifies separation and purifi cation of tissue plasminogen activator by acting as a preferential inhibitor.Tissue plasminogen activator is a possible solvent for blood clots (thromboses) in man.Extraction of the inhibitor from seeds of Ery thrina section Cajfrae is being carried out commercially by a pharmaceu tical company in South Africa.

SY N O N Y M Y OF ALL SU B G E N E R A A N D SECTIONS R E PR E SE N T E D IN SO U T H E R N AFRICA
I. Subgenus M icropteryx (Walp.)Bak. in Hook, f..The Flora of British India 2.1: 189 (1876); Krukoff & Barneby: 339 (1974) Verde.: 542 (1971); Krukoff & Bameby: 348 (1974)         Trees of this species occur in open savanna, often on rocky outcrops where they may have been afforded some degree of protection from fire damage.Juvenile plants seem rare in the wild which suggests that some form of protection, especially from fire, should be afforded this species.Erythrina latissima is recorded from Zimbabwe, Mozambique, Swaziland, Transvaal, Natal and the eastern Cape (Figure 1).Late winter/spring-flowering.
This winter/early spring-flowering species is distin guished from E. caffra, with which it has often been confused, by its smaller stature; its narrower, chevron shaped inflorescences; the scarlet (as opposed to vermilion red) colour of its vexilla; its longer, narrower, less strongly arcuate vexilla which do not spread or reflex at maturity but enfold and conceal the inner floral parts.The fruit and seed of E. lysistemon and E. caffra are alike.These species have not yet achieved perfect reproductive isolation.Where their ranges overlap they hybridise.The hybrid, E. x dyeri, is fertile.
Erythrina lysistemon is tolerant of a wider range of climatic and soil types than is E. caffra and has a wider distribution range (Figure 4).North of the Flora region it occurs in Mozambique, Zimbabwe, Zambia, Malawi and Tanzania.This winter/early spring-flowering species is limited in its distribution to the eastern Cape and southern Natal coastbelt with outlying populations in forest in northern Zululand and on Inhaca Island off Maputo which may or may not be natural (Figure 5).It usually occurs in coastal and streambank forests in deep sandy soils.It differs from other southern African members of subgenus Erythrina in having a widely gaping flower (Figure 3.8-3.24).
The amount of variation in leaflet shape in this species is noteworthy.Specimens with broadly ovate leaflets occur mainly in the southern part of the distribution range and those with long, narrowly hastate leaflets further north.
The profusely branched, perennial aerial system of this species makes it.by definition, a shrub, yet the greatiy enlarged subterranean rootstock is a modification best developed elsewhere in the genus in the suffrutescent species.This species is isolated in the genus by the combination of habit, small leaflets, unique colouration of the vexilla, unusual shape and proportions of alae and carina.aculeate fruit and brown seeds.

Icon: H ennessy: t. 1911 (1985).
Tree, juvenile parts densely or sparsely hirsute.Leaves hysteranthous, resembling those of E. latissima.but smaller.Inflorescences precocious, ± horizontal, compact; flowers gaping at anthesis.Calyx olive green; tube spathaceous, splitting ± abaxially to the base; lobes distinct, to 5 mm long, or obsolete.Corolla: vexillum bright scarlet, spread and partly reflexed, smaller than those of E. latissima and E. caffra: alae exceeding carina; carina segments partly connate as in E. caffra.Stamens diadelphous or vexillary stamen absent.Fruit unknown.This apparently sterile hybrid taxon is known only from the Port Shepstone District in southern Natal (Figure 8) where the putative parents, E. latissima and E. caffra are sympatric.One tree in the garden of the Natal Herbarium in Durban was established from a truncheon planted in 1957.Like E. x coddii this hybrid is the product of a cross between parents belonging to different subgenera and shows some characters of each subgenus.It differs from E. x coddii mainly in its consistently more coriaceous leaflets; more nearly horizontal flowers; more widely gaping flowers and brighter red vexilla.Spring-flowering.This fertile hybrid of the two members of section Caffrae occurs in areas where the parents are sympatric (Figure 8) or grow together in cultivation.At maturity the hybrid is a slightly smaller tree than E. caffra.The inflorescence shape, attributable to the gaping, ± horizontal flowers, is like that of E. caffra.but the colour is like that of E. lysistemon.The extent to which introgression occurs is not known.Winter-flowering.The first recorded gathering of this rare (Figure 8), apparently sterile hybrid was made at Rustenburg in 1911.Subsequently a second specimen was discovered on a koppie near Nylstroom and several plants were established in the gardens of Shangri La Guest Farm from cuttings taken from the wild specimen.In stature, foliage and the synanthous condition, this hybrid resembles E. humeana; in flower morphology it closely resembles E. lysistemon.Its sterility confirms the validity of the separation of sections Caffrae and Humeanae.Late winter/springflowering.

E. g la iu a
Erythrina fusca has a w ider distribution range than any other species of Erythrina, occurring naturally on three continents, Africa.Asia and South America in the littoral and sublittoral zones, and on many tropical islands.Its seeds are reputed to be distributed by ocean currents and in river water.It was one of the first tree species to recolonise the island of Krakatau after the cataclysmic volcanic eruption of 1883.
The common name 'Cock's comb' coral tree from the Latin crista-galli (cock's comb), is an allusion to the short fan-shaped free portion of the stamens which is exserted beyond the keel.
Characters which separate E. crista-galli from E. falcata are summarised in the key to exotic species.
Indigenous in subAndean southern Peru, Bolivia, eastern Brazil, Paraguay and northern Argentina, this species is cultivated as an ornamental street tree in parts of South America, in Australia and in South Africa; several trees are known in Johannesburg.Fruit and seeds have been collected from one of the Johannesburg plants (Herdman s.n.sub J 48618).All the trees in our area are redflowered, but the occasional white-flowered form has been recorded in Bolivia.Spring/summer-flowering.
Widely cultivated in the tropics as an ornamental tree and frequently grown for shade in coffee and cacao planta tions, this species is indigenous in Venezuela, Panama, subAndean Colombia, Ecuador, Peru and Bolivia.Mature specimens exist in the Durban area where, although fruit set is initiated, the follicular pods abort early and no mature seeds have been observed.E. poeppigiana is easily recognisable as its cup-shaped stipels are unique in the genus.Spring-flowering.
An African species indigenous in parts of Malawi, Mozambique and possibly in the Triangle region of Zimbabwe, now in cultivation in South Africa in the Durban area where it was introduced by Dr Vincent Wager in 1951.Flowering of the Durban trees is erratic, occurring in late summer with not all the trees flowering in a single year.Fruit and seed development occur and the number of plants grown from seed is rapidly increasing.The formidable armament of the stems makes propagation from truncheons difficult.This is a spectacular species which requires a lot of water.The heavy armament and palmatilobed leaflets make this species easily recognisable.Section Stenotropis (Hassk.)Krukoff in Lloydia 37: 359 (1974).Erythrina subgenus Stenotropis (Hassk.)Bak.: 188 (1876).Erythrina 'group' Speciosae Krukoff: 243 (1939a)
The history of the introduction of this hardy taxon into southern Africa in unknown.It is widely cultivated in the western Cape, southern Cape, parts of Namibia and at least one specimen (purchased in the western Cape) is estab lished in Pietermaritzburg, Natal.The plants agree with the description of E. x sykesii except that the carina is invariably partly connate in locally cultivated plants.E. X sykesii was described from plants cultivated in New Zealand and Australia and in photographs of the Australasian plants made by Dr Ian W hitton, the habit, inflorescence and flower structure appear identical to those of the specimens grown in southern Africa.
The parentage of the hybrid is unknown.In inflores cence shape and attitude; the well-developed triangularsubulate abaxial calyx tooth; the scarlet colour of the vexillum and in shape and relative proportions of alae and carina, the hybrid resembles E. speciosa.In shape of leaflets; the asymmetrically bilabiate calyx; the gaping flower with exposed stamens and in connation of the relatively large carina segments, the hybrid is like E. caffra.Both E. speciosa and E. cajfra are cultivated in Australasia and their flowering times overlap.Although Krukoff & Barneby (1974) have suggested E. lysistemon as a putative parent because the hybrid possesses a calyx of the type known only in section Caffrae, this seems unlikely as E. lysistemon has a closed flower with included stamens.The stature of the mature trees more closely resembles that of E. cajfra than that of E. lysistemon.Until the hybrid is successfully resynthesised, the parentage of this taxon remains speculative.Winter/spring-flowering.

SP E C IM E N S E X A M IN E D (ERYTHRINA)
The specimens are listed alphabetically according to the name of the collector.The figures in parentheses refer to the number of the taxon in the text.The herbaria in which the specimens examined are housed, are indicated by the letter codes of Holmgren & Keuken, Index herbariorum (1974), except that of the University of Durban-Westville, UDW, which is as yet unlisted.
B othalia 21.1 (1991)  A genus of ± 100 circumtropical and subtropical species, three of which are indigenous in the FSA region.
Pending revision of the genus on a world basis, Mucuna is retained in its broad sense, with two well-defined sub genera, Mucuna and Stizolobium (P.Br.) Prain.Both subgenera are represented in southern Africa.

PO LLINATION A N D E C O N O M IC IM PORTANCE
Red-flowered species of Mucuna are mostly birdpollinated; green or pale-flowered species mainly bat-pollinated and Kenneally (in Verdcourt 1980) has suggested that at least one Australian species, M. reptans Verde., a prostrate plant with musk-scented, mottled blackish purple, red, yellow, or green flowers, is rodentpollinated.
Despite the attractiveness of the flowers of many species the genus has little economic value because the irritant bristles make the material difficult, even dangerous to handle.Exceptions are M. nova-guineensis Scheff., 'red jade vine', a woody liane cultivated for its spectacular flowers and M. pruriens (L.) DC. var.utilis (Wall, ex Wight) Bak.ex Burck.'Florida velvet bean', an innocuous, large-seeded cultivar of unknown origin cultivated as a fodder crop.Both these taxa are grown in the FSA region.
Ingestion of irritant bristles of many species induces severe diarrhoea.In primitive medicine, potions containing irritant bristles derived mainly from pods were employed as vermifuges.Severe dermatitis and inflammation of the eyes result from contact with the urticating bristles, and inflammation of nasal and buccal mucosa, laryngitis and gastro-intestinal disturbance from inhalation and/or ingestion of the bristles.Cases of dementia and even death induced by accidental exposure of domestic animals to M ucuna bristles have been reported (Burtt Davy 1932).
Vernacular names of the two indigenous species of subgenus Stizolobium are hell-fire bean, brandboontjie, jeukpeul and isifefeta.
I. Subgenus M ucuna: Verde.: 561 (1971    Recorded in the FSA region from two localities.Mdloti River estuary and Sihadla.Kosi River system in Natal (Figure 10).from Mozambique, Uganda.Tanzania.Kenya.Zaire.Zanzibar Is, Mascarene Is, Seychelles Is, and also India, Malesia, China.Taiwan.Japan, Australia and Polynesia.Over much of its range its habitat is coastal, near water, on forest margins, but in East Africa it has been recorded inland from altitudes up to 1 140 m.
The Mdloti population is rooted on the landward side of an estuarine fringe of Barringtonia racemosa (Lecythidaceae).with the vine-like stems extending into the upper canopy.The pendent, green-flowered, pseudoumbellate inflorescences are in the canopy and very difficult to discern.Anthesis occurs simultaneously in an inflorescence.Nectar production is copious.Olive sun birds (Cyanomitra olivacea) visit the flowers, yet no seed-set has been observed in this population, therefore it is assumed that the sunbirds are not effective pollinating agents for this species.This assumption is strengthened by the observation that fallen flowers are untripped, with anthers and stigma included in the carina.It is thought that M. gigantea is chiropteriphilous and that the more southerly local population may lie south ol the normal range of the effective pollinator(s).The wild form, M. pruriens var.pruriens has been recorded from only two localities in the FSA region to date (Figure 10).Elsewhere widely distributed in tropical Africa, Madagascar, Asia and tropical America.The innocuous cultivated form, var.utilis, which is larger in all its dimensions than var.pruriens and is of unknown origin, is widely used as a fodder crop and as green manure.
M. pruriens var.pruriens is distinguished from M. coriacea mainly by its thinner, larger, usually acute or acuminate leaflets; the silvery calyx indumentum; the longitudinally wrinkled pericarp and the white aril.
Material of this African species from Tanzania, Zambia, northern Mozambique and Malawi has been placed in subsp.coriacea and larger-flowered forms from Tanzania, Uganda.Zaire, Zimbabwe.Angola, southern Mozambique and southern Africa in subsp.irritans (Figure 10).The indumentum of the pericarp of subsp.irritans is heavier than that of subsp.coriacea, whereas that of the leaves is more dense in subsp.coriacea.The merit of the separa tion of two subspecies is questionable as intermediates exist.
Characters which distinguish M. coriacea from M. pruriens are mentioned under M. pruriens.

SPECIMENS EXAMINED (MUCUNA)
The specimens are listed alphabetically according to the name of the collector.The figures in parentheses refer to the number of the taxon in the text.The Herbaria in which the specimens examined are housed, are indicated by the letter codes of Holmgren & Keuken, Index herbariorum (1974), except that of the University of Durban-Westville, UDW. which is as yet unlisted.
FIG U R E 7 .-Distribution o f E rythrina zeyheri.

Lugg s.n. sub N H 4 0 4 7 7 ( N H ); M ugw edi 19 (J); Ward 2 954 (N H ).
Tree with stout bole, juvenile parts densely or sparsely hirsute.Leaves hysteranthous, variable, intermediate in texture, size, shape and indumentum between those of the putative parents, E. latissima and E. lysistemon.Inflores cences precocious, ± horizontal, compact; flowers slightly gaping at anthesis.Calyx dull reddish-brown; tube spathaceous splitting abaxially to the base; lobes distinct, of varying lengths.Corolla: vexillum deep scarlet, somewhat spreading, narrower than that of E. latissima; alae exceeding carina; carina segments partly connate as in E. lysistemon, or free as in E. latissima.Stamens diadelphous vexillary filament partly coherent.Fruit unknown.Specimens of this apparently sterile hybrid taxon are at present known from the Hluhluwe Game Reserve in northern Natal, from Ndwedwe in Natal, from the northern Transvaal and outside the Flora region from Harare in Zimbabwe (Figure8).The putative parents, E. latissima and E. lysistemon are sympatric in these areas and the hybrid shows characters which are intermediate between those of these two species.Spring-flowering. Vouchers:
Tree, intermediate between its putative parents E. lysistemon and E. caffra, therefore impossible to dis tinguish accurately from either in the vegetative phase.Inflorescences compact, ± horizontal, precocious; flowers gaping, not deflexed, resembling those of E. caffra.Calyx tube campanulate, bilabiate at anthesis, brown; lobes obsolete except the abaxial lobe prognathous in bud.Corolla', vexillum bright scarlet like that of E. lysistemon, spread and reflexed like that of E. caffra, shorter than that of either parent; alae and carina intermediate in size and shape.Stamens intermediate.Fruit and seeds indistinguish able from those of either parent.
Shrub up to 3 m tall.Leaves sparsely aculeate; leaflets long-acuminate from a broadly ovate base, like those of some forms of E. humeana.Inflorescences compact, ± horizontal, contemporary with the leaves; flowers deflexed, not gaping.Calyx russet, narrowly campanulate, shortly bilabiate at anthesis; lobes obsolete.Corolla: vexillum red.subacute like that of E. lysistemon; alae, carina and sta mens similar to E. lysistemon.Fruit unknown.
Indigenous in south-eastern Brazil and cultivated in tropical South America.New Zealand, Australia and in South Africa in the Durban area where flowering occurs in late winter or early spring contemporary' with E. lysiste mon and E. caffra.The sterile hybrid taxon, E. x sykesii Barneby & Krukoff (E.hybrida of horticultural literature) which is cultivated in parts of southern Africa may have as one of its parents E. speciosa.