Plagiosiphon

Taxonomy

Plagiosiphon H.A.T. Harms In Engler et Prantl, Nat. Pflanzenfam. Nachtr. 1: 194. Oct 1897.

Subfamily: Caesalpinioideae.
Phylogenetic Number: 1.4.12.
Tribe: Detarieae.
Group: Hymenostegia.
Species Studied - Species in Genus: 2 studied; 5 in genus.

Description

Fruit: A legume; unilocular; 5.5–10 cm long; 2–4.5 cm wide; 0.3–0.5 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; not plicate; not twisted; symmetrical, or asymmetrical; with 1 straight and 1 curved suture; widest near apex (oblong, but rather abruptly narrowed on one side to an apiculate apex); not inflated; compressed; without beak; tapered at apex; aligned with longitudinal axis of fruit to oblique with longitudinal axis of fruit; rounded at base; oblique 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 ventral margin usually thickened sutural areas; wing(s) absent; substipitate; with all layers dehiscing; splitting along suture(s). Dehiscence of valves along both sutures (initially along ventral margin); active; with valves separately enrolling. Replum invisible. Epicarp dull; monochrome; reddish brown; with surface texture uniform; velvety or densely pubescent and indurate; with hairs erect; eglandular; without spines; not smooth; with elevated features; veined; obliquely veined relative to fruit length; not tuberculate; not exfoliating; without cracks; without embedded tissue, much thicker than epicarp, running from base to apex. Mesocarp present; surface not veined; 3-layered; without balsamic vesicles; with fibers; without reniform canals; with fibers over mealy tissue over solid layer; ligneous. Endocarp present; visible; dull; opaque; monochrome; grayish brown or brown; without adhering pieces of testa; subseptate; not exfoliating; remaining fused to mesocarp and epicarp; entire. Seed(s) 1–4; length transverse to fruit length; neither overlapping nor touching; in 1 series. Funiculus 0.1–1 mm long; of 1 length only; flattened; straight. Aril absent.

Seed: 17–19 mm long; 12–13 mm wide; 4–5 mm thick; not overgrown; not angular; asymmetrical; D-shaped; 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; dull; not modified by a bloom; colored; monochrome; dark reddish brown; glabrous; not smooth; with elevated features; rugose; coriaceous. 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 mm long; with curved outline; elliptic; apical at apex of radicle tip; flush; not within corona, halo, or rim. Lens not discernible. 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; partially concealing radicle (only tip exposed); notched at radicle and 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; centered between cotyledons. Plumule rudimentary; glabrous.

Distribution

Guineo-Congolian forest.

Old World; Africa (Guineo-Congolian forest).

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.