A tree of 15–30 ft. or more with a widely spreading crown; branches unarmed, early glabrous. Leaves 1/2 ft. long more or less (3–7 in.), rachis puberulous eglandular; pinnæ alternate, usually 10–13 on each side; leaflets opposite, multi-(30–60) jugate, closely distichous, sessile, linear-oblong, more or less falcate, obtuse or subacute, glabrous or nearly so, venation obscure, 2–3 lines long, about 1/2 line broad. Spikes 2 1/2–4 in. long, in axillary and terminal panicles usually exceeding the leaves; peduncles rusty-pubescent or puberulous, bracts 0 at flowering. Flowers whitish or greenish-yellow, about 2 lines long, minutely pedicellate, pedicel articulated, the microscopic base persisting after the fall of the flower. Calyx cupuliform, 5-dentate. Petals linear-oval, acute. Stamens exserted, filaments filiform, consolidated at base with the disk and petals; anther-gland large, caducous. Ovary glabrous, subsessile. Style at length as long as ovary. Legume 1 ft. long more or less, 1–1 1/4 in. broad, flat, straight, coriaceous, smooth, obscurely veined, continuous, the valves often cohering by the dorsal suture after dehiscence. Seed compressed with a membranous laterally dilated wing as broad as the valve.
