Gagnebina

Taxonomy

Gagnebina N.M.J. de Necker ex A.P. de Candolle Prodr. 2: 431. Nov (med.) 1825.

Subfamily: Mimosoideae.
Phylogenetic Number: 2.3.33.
Tribe: Mimoseae.
Group: Dichrostachys.
Species Studied - Species in Genus: 2 studied; ca. 4–5 in genus.

Description

Fruit: A legume; unilocular; 1.1–6 cm long; 0.4–2.5 cm wide; 0.1 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; oblong to linear; not inflated; compressed; without beak; rounded at apex, or emarginate at apex (if winged); aligned with longitudinal axis of fruit; short tapered at base; aligned with longitudinal axis of fruit; with the apex and base uniform in texture; coriaceous; seed chambers externally visible, or invisible; margin not constricted; margin without sulcus; margin plain, or embellished; margin with wing(s); wing(s) present, or absent (if present, transversely striate membranous wing); wing(s) 2; wing(s) 0.1–10 mm wide; wing(s) sutural; wing(s) on both sutures; stipitate; with the stipe 10 mm long; indehiscent, or with all layers dehiscing; splitting along suture(s). Dehiscence of valves along both sutures (remaining attached to sutures); apical and down; passive. Replum invisible. Epicarp glossy; monochrome; brown; with surface texture uniform; when young pubescent and indurate and glabrate (at maturity); with hairs erect; with simple hairs; eglandular; without spines; smooth and not smooth (knobbed over seed chamber); with elevated features; veined; transversely veined relative to fruit length; not tuberculate; knobbed (over seed chambers); not exfoliating; without cracks; without embedded tissue, much thicker than epicarp, running from base to apex. Mesocarp absent. Endocarp present; visible; dull; opaque; monochrome; within seed chambers brown and white (between seeds); smooth; without adhering pieces of testa; septate to subseptate; not exfoliating; entire. Seed(s) 5–7; length oblique to fruit length; neither overlapping nor touching; in 1 series. Funiculus 1.5 mm long; of 1 length only; filiform; sharply curved. Aril absent.

Seed: 2.5–4 mm long; 1.5–3 mm wide; 0.1 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; greenish brown; glabrous; smooth; coriaceous. Pleurogram present; 75 %. Pseudopleurogram absent. Fracture lines absent. Rim absent. Wing(s) absent. Raphe not visible. Hilum present; visible; without faboid split; punctiform; subapical to radicle tip; flush; not within corona, halo, or rim. Lens discernible; 0.1–0.2 mm long; with margins curved; circular to elliptic; not in groove of raphe; mounded; dissimilar color from testa; yellow; not within corona, halo, or rim. Endosperm present; 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; partially concealing radicle; with lobes; with lobes touching (auriculate); without basal groin formed by lobes; with the interface division terminating at base of radicle; without margins recessed; inner face flat; glabrous on inner face. Embryonic axis straight to deflexed (slightly); 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 rudimentary; glabrous.

Distribution

Generic Notes

Renvoize (1972) placed G. commersoniana in Dichrostachys based on fruit morphology, not flower morphology (flowers are similar to those of Gagnebina). By doing this he expected species of Gagnebina to have winged fruits and species of Dichrostachys to have wingless fruits; whereas Dichrostachys species would have wingless fruits, the placement of G. commersoniana in Gagnebina does not adversely impact on the winged fruits in this genus. The wings on G. tamariscina fruits vary from virtually wingless to winged, from 0.1 to 10 mm wide. Lewis and Elias (1981) support the placement of G. commersoniana in Gagnebina.