Adenanthera

Taxonomy

Adenanthera C. Linnaeus Sp. Pl. 384. 1 Mai 1753.

Phylogenetic Number: 2.3.09.
Tribe: Mimoseae.
Group: Adenanthera.
Species Studied - Species in Genus: 5 studied; 12 in genus.

Description

Fruit: A legume; unilocular; 8–23 cm long; 10–25 cm wide; 0.5–1.2 cm thick; length less than twice as long as width; with deciduous androecial sheath; with deciduous corolla; with deciduous calyx; without orifice formed by curving of fruit or fruit segments; straight to 1-coiled; not plicate; twisted, or not twisted; symmetrical; linear to oblong; not inflated; compressed; without beak; short tapered at apex; aligned with longitudinal axis of fruit; tapered at base; aligned with longitudinal axis of fruit; with the apex and base uniform in texture; coriaceous to ligneous; seed chambers externally visible; margin not constricted to constricted (slightly); margin slightly constricted along both margins; margin without sulcus; margin plain; wing(s) absent; stipitate; with the stipe 10–20 mm long; with all layers dehiscing; splitting along suture(s). Dehiscence of valves along both sutures; apical and down, or medial and up and down (perhaps); active; with valves coiling (into several coils exposing inner endocarp surface). Replum invisible. Epicarp dull; monochrome; brown to black; with surface texture uniform; glabrous; eglandular; without spines; smooth; not veined; not tuberculate; exfoliating, or not exfoliating; with cracks (later); without embedded tissue, much thicker than epicarp, running from base to apex. Mesocarp absent, or present; surface not veined; 1-layered; without balsamic vesicles; without fibers; without reniform canals; spongy. Endocarp present; visible; glossy; opaque; monochrome; tan; without adhering pieces of testa; nonseptate (but chambered); not exfoliating; remaining fused to mesocarp and epicarp; entire. Seed(s) 10–12; length transverse to fruit length; neither overlapping nor touching; in 1 series. Funiculus 3–5 mm long; of 1 length only; thick; plicate to straight. Aril absent.

Seed: 5–10 mm long; 5–10 mm wide; 3–6 mm thick; not overgrown; not angular; symmetrical; ovate; compressed; with surface smooth; without visible radicle and cotyledon lobes; without hilar sinus; without umbo on seed faces; without medial ridge on each face. Cuticle not exfoliating; not inflated; not wrinkled. Testa present; without pieces of adhering epicarp; not adhering to endocarp; free from endocarp; glossy; not modified by a bloom; colored; monochrome, or bichrome; red, or black and red (at apex); glabrous; smooth; osseous. Pleurogram present (apically connected or nearly so); ca. 100 %. Pseudopleurogram absent. Fracture lines present, or absent. Rim absent. Wing(s) absent. Raphe not visible. Hilum present; fully concealed; concealed by funicular remnant; without faboid split; punctiform; apical at apex of radicle tip; flush (on edge of hilar depression); not within corona, halo, or rim. Lens discernible; 0.3–0.8 mm long; with margins straight, or curved; oblong; elliptic; not in groove of raphe; slight mounded to flush (but in hilar depression); same color as testa; red; not within corona, halo, or rim. Endosperm present; thick to thin; not pluglike and not resembling tip of radicle; adnate to testa. Cotyledons smooth; both outer faces flat; both the same thickness; both more or less of equal length; not folded; margin entire 180 degrees from base of radicle; similar at apex; completely concealing radicle; split over radicle; with the interface division terminating at base of radicle; without margins recessed; inner face flat; glabrous on inner face. Embryonic axis straight; parallel to length of seed; without a joint evident between the radicle and the cotyledons. Radicle differentiated from cotyledon; straight with embryonic axis; centered between cotyledons. Plumule moderately developed; glabrous.

Distribution

Tropical Asia and Pacific, With A. pavonina widely grown elsewhere.

Old World; tropical Southwest Asia, Madagascar, India, Indochina, China, Indonesia and the Philippines, and Pacific (with A. pavonina widely grown elsewhere).

Generic Notes

All the studied species have seed with bright red monochrome or dichrome (With black) testa. This is a unique character in the Mimosoideae, but it is found in seeds of several genera in the Faboideae and apparently not found in seeds of the Caesalpinioideae. Adenanthera seeds are readily separated from the faboid seeds by the apical hilum and presence of the pleurogram. Hutchinson (1964) erroneously described fruit "often divided between the seeds by a septum continuous with the endocarp" and seeds "mostly enclosed by a thin pulp." Nielsen and Guinet (1992) revised the genus, describing two new species, and their species count is used.