Description from Flora of China
Herbs, twining. Leaves pinnately 3-foliolate. Inflorescence axillary, racemose, sometimes with apetalous cleistogamous flowers at base or 1-3 in axils of lower leaves, nodes not swollen but sometimes more than 1-flowered. Bracts persistent or deciduous. Calyx tubular, 4- or 5-lobed. Corolla longer than calyx; petals subequal; standard obovate or obovate-elliptic, glabrous, base clawed, with inconspicuous auricles; keels slightly curved. Stamens diadelphous; vexillary stamen free; cleistogamous flowers with only 3-5 anthers. Ovary sessile or subsessile, with sheathing disk at base; ovules many; style glabrous; stigma small, terminal. Legumes of 2 types: normal and underground; normal legumes linear-oblong, dehiscent, compressed, unjointed, few seeded; underground legumes usually orbicular or ellipsoidal, indehiscent, 1-seeded. Seeds subglobose or ovoid; hilum short, lateral; aril not developed.
About five species: tropical Africa, E Asia, North America; three species (two endemic) in China.
(Authors: Sa Ren (萨仁); Michael G. Gilbert)