Piper, C ontr. U.S. Natl. Herb. 20:574.1925
Twining herbaceous vine. Leaves trifoliolate; petioles 3-9 cm long, densely pubescent; rachis 1.5-4.5 cm long; leaflets lanceolate-elliptic, rounded to acute at apex, obtuse at base, 9-19 cm long, 4-12 cm wide, glabrous above, sparsely strigillose below. Flowers lavender, in axillary racemes; peduncles ca 10 cm long; rachises to 20 cm long; pedicels to 2 mm long, elongating to 1 cm and thickening greatly in fruit; calyx bilabiate, glabrous, to 13 mm long and 7 mm wide, with the 2 superior teeth ± rounded and to 5 mm long, the lower 3 teeth acute and to 2 mm long; standard pale lavender, to 2.5 cm long, the margins revolute, strengthening petal; wings and keel white with lavender tips, somewhat shorter than standard, the keel petals fused only briefly below their summit; stamens diadelphous, to 2 cm long, arching into keel petals; filaments united about four-fifths of their length; style ± equaling the stamens, apparently receptive when pollen is shed; nectaries 2, on either side of the ovary. Legumes to 20 cm long, to 3.5 cm wide, glabrous, brown, the upper margin broad with prominent submarginal ridges and an apical beak; valves at maturity twisting open violently and throwing the seeds; seeds 6-9, vertically oriented, to 2 cm long, 1.5 cm wide, and 1.2 cm thick, brown with dark brown and black markings, buoyant. Croat 4794.
Occasional, in open areas, especially along the shore near the dock. Flowers from November to February (rarely later). The fruits ripen mostly from February to June, with most mature perhaps by April.
May be confused with C. brasiliensis Mart. ex Benth., which differs chiefly in having the leaves more broadly ovate and the seeds not buoyant.
The nectaries of the flower can be approached by the pollinator only at the open side of the staminal cluster. Bees land on the standard, which is strengthened by its revolute margin and supported beneath by the two large calyx lobes. In forcing its way in, the bee pushes the keel upward and rubs the stationary stigma and anthers with its back.
Panama to the northern Amazon basin and eastern Brazil; West Indies. In Panama, known only from tropical moist forest in the Canal Zone, San Blas, and Panama.