Brachystegia

Taxonomy

Brachystegia G. Bentham In Bentham et J. D. Hooker, Gen. 1: 582. 19 Oct 1865.

Subfamily: Caesalpinioideae.
Phylogenetic Number: 1.4.76.
Tribe: Detarieae.
Group: Brachystegia.
Species Studied - Species in Genus: 10 studied; ca. 30 in genus.

Description

Fruit: A legume; unilocular; 5–30 cm long; 2–11 cm wide; 0.5–1 cm thick; 2–9 times longer than wide; with deciduous androecial sheath; with deciduous corolla; with deciduous calyx; without orifice formed by curving of fruit or fruit segments; straight to curved; not plicate; not twisted; symmetrical, or asymmetrical; oblong; with 1 straight and 1 curved suture; widest near apex; not inflated; flattened; without beak; long tapered at apex to tapered at apex (short); aligned with longitudinal axis of fruit to oblique with longitudinal axis of fruit; rounded at base; straight or right angled with longitudinal axis of fruit; with the apex and base uniform in texture; ligneous; seed chambers externally invisible; margin not constricted; margin without sulcus; margin embellished; margin with flange(s) (one on each valve, up to 8 mm wide); wing(s) absent; stipitate; with the stipe 6–20 mm long; with all layers dehiscing; splitting along suture(s). Dehiscence of valves along both sutures (initially along ventral margin); active; with valves elastically and separately loosely enrolling, or twisting. Replum invisible. Epicarp dull to glossy, or glaucous (rarely); monochrome, or multicolored; mottled (with combinations of pink, purple, red and yellow on); brown to purple (or bluish black); with surface texture uniform; glabrous; eglandular; without spines; not smooth; with elevated features, or recessed features; not veined; not tuberculate; lenticular, or warty, or papillose, or scurfy (warty fruits are scurfy fruits which have become warty as a result of insect infestation); punctate; not exfoliating; without cracks; without embedded tissue, much thicker than epicarp, running from base to apex. Mesocarp present; surface not veined; 2-layered; without balsamic vesicles; with fibers; without reniform canals; with fibers oblique over solid layer; ligneous. Endocarp present; visible; dull; opaque; monochrome; brown to reddish brown; smooth and spongy (usually smooth under seed and spongy around seed); without adhering pieces of testa; subseptate to nonseptate; not exfoliating; remaining fused to mesocarp and epicarp; entire. Seed(s) 1–11; length transverse to fruit length; neither overlapping nor touching; in 1 series. Funiculus 0.1–1.5 mm long; of 1 length only; flattened; straight. Aril absent.

Seed: 10–35 mm long; 7.5–30 mm wide; 3–5 mm thick; not overgrown; angular, or not angular; symmetrical; ovate to circular, or quadrangular; flattened; 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 to dull (occasionally cuticle thick and whitish); not modified by a bloom; colored; monochrome; reddish brown; glabrous; smooth, or not smooth; with elevated features; rugose, or warty (minutely); osseous. Pleurogram absent. Pseudopleurogram absent. Fracture lines absent. Rim absent. Wing(s) absent. Raphe not visible. Hilum present; visible; without faboid split; larger than punctiform; 0.1–2.5 mm long; with curved outline; elliptic; not within corona, halo, or rim. Endosperm absent. Cotyledons smooth; both outer faces convex; 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, or partially concealing radicle (only tip exposed); notched at radicle, or entire 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; centered between cotyledons. Plumule rudimentary; glabrous.

Distribution

Guineo-Congolian forests and south-central Africa.

Old World; South-central Africa (including Guineo- Congolian forests).
 

Generic Notes

Brenan (1967) noted that the warts on the fruits of some species were caused by insects, and White (1962) noted that "the finely scurfy surface of pods (B. allenii and B. boehmii P.H.W. Taubert) is not to be confused with warts due to insects." The pleurogramlike or pseudopleurogramlike line on the face of seeds represents a difference in seed thickness.

Tribal Notes

Tribe Detarieae

Bruneau et al. (2000) carried out extensive phylogenetic analyses of tribes Amherstieae and Detarieae. They concluded that they form a single monophyletic group. Therefore, they supported Polhill's (1995a, 1995b) decision to unite the two tribes.