Cal obconic, nearly regular, 4-lobed by fusion of the upper 2, the lobes nearly equal, somewhat exceeding the tube; standard broadly obovate, narrowed to a short claw, obscurely auricled; wings oblong, blunt, auricled at base above the slender claw, slightly shorter than the straight, semi-obovate, short-clawed keel-pet; stamens 10, diadelphous; ovary pubescent; style glabrous, fr narrowly oblong, flat, few-seeded, twisted after dehiscence; twining or trailing perennial herbs with pinnately trifoliolate lvs, minute stipules and bracts, and short racemes; fls small, purplish, often 2 or 3 at a node, each closely subtended by a pair of minute bracteoles. 50, mostly warm New World.
The proper application of the names G. regularis and G. volubilis is in dispute, and the traditional usage of G. regularis, in particular, may well be incorrect. We here follow the tradition, rather than accepting newer interpretations that are also debatable.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.