Cal-tube hemispheric, slightly oblique; lobes 5, subequal, shorter than the tube; standard rotund, its sides folded over the other pet; wings semi- obovate, coherent with the keel; keel-pet linear-oblong, at the summit incurved and spirally coiled; stamens 10, diadelphous; style bearded along the upper side, spirally coiled and thickened beyond the middle; fr terete or flattened, with few-several seeds; twining or erect herbaceous perennials with pinnately trifoliolate lvs, small few-nerved stipules and bracts, and small to medium- sized fls each closely subtended by a pair of minute bracteoles. 200+, mainly warm New World.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.