Liana, becoming shrubby elsewhere in open areas, lacking tendrils; younger stems reddish-brown, to 12 mm diam. Leaves trifoliolate; stipules lanceolate, ca 7 mm long, pubescent, persistent; petioles 1-15 cm long, reddish-villous; rachis of terminal leaflet to 30 mm long; petiolules of lateral leaflets ca 4 mm long, pulvinate and articulate at apex; leaflets elliptic to obovate, abruptly short-acuminate, rounded at base, 6-22 cm long and 3.5-11 cm wide, dark above, paler below, glabrous above, +/- pubescent below at least on the midrib. Racemes axillary, to 30 cm long; bracts and bracteoles ovate, acute, ca 7 mm long, striate; pedicels to 4 mm long; calyx to 3.5 cm long and 1 cm wide, the lobes sharply and abruptly acuminate, the carinal tooth to 8 mm long, the others somewhat shorter; standard white with divergent red lines at center, often infused throughout with pink, rounded at apex, the sides folded over other petals, to ca 8 cm long; wings white, fused to keel above, the keel white, the 2 sides free except at +/- twisted apex, enclosing style and stamens, the wings and keel each to ca 6.5 cm long; stamens of 2 lengths, the free stamen and alternate stamens of the staminal tube short, the others slightly longer, the longest to ca 5.5 cm long, considerably exceeded by the densely pubescent style. Legumes on stipes 3 cm long, linear, flattened, sometimes broader toward the apex, to 27 cm long and 2.5 cm wide, abruptly long-acuminate (the acumen to 4 cm long), softly brown-villous; valves twisting when dry at maturity and capable of straightening or twisting repeatedly with changes in humidity; seeds 7-11, ca 12 mm long, 10 mm wide, and 5 mm thick, black. Croat 4853, 8497. Common in the forest, growing to the top of the canopy, and at the edges of clearings. Flowers from October to May, mostly early in the dry season, in January and February. The fruits mature from January to May, mostly in April and May. Panama to the Guianas, northern Brazil, Peru, and Ecuador. In Panama, known principally from tropical moist forest in the Canal Zone, Colón, Chiriqui, Veraguas, Panama, and Darien; known also from tropical dry forest in Panama (Taboga Island) and from premontane wet forest in Chiriqui.