Description from Flora of China
Herbs, twining or procumbent. Stems somewhat woody at base. Leaves pinnately 3-foliolate, stipulate; leaflets stipellate. Racemes axillary. Flowers small or moderately large, clustered at nodes of inflorescence rachis. Pedicels very short; bracts and bracteoles small, deciduous. Calyx campanulate or tubular; teeth 5, upper 2 ± connate. Corolla blue or purple; standard obovate, with 2 incurved auricles at base; wings narrow, auriculate, adnate to keel; keel shorter than wings, blunt and slightly curved. Stamen opposite to standard, free, others connate. Ovary sessile, many ovuled; style filiform; stigma capitate, small and terminal. Legumes linear or oblong, dehiscent, slightly compressed or biconvex, transversely corrugated between seeds. Seeds rounded, slightly compressed, without strophiole.
Five or six species: tropical and subtropical America and the Antilles; one species (introduced) in China.
(Authors: Sun Hang (孙航); Mats Thulin)