Description from Flora of China
Herbs, climbing or prostrate, rarely erect, with tubers. Leaves pinnately 3-foliolate; stipules produced below point of insertion; leaflets stipellate. Flowers solitary or in axillary racemes with swollen nodes. Bracts small, very caducous; bracteoles larger, membranous, persistent for a time. Calyx 5-toothed, 2 upper teeth connate into entire or bifid lip. Corolla lilac or violet, exserted from calyx; standard suborbicular, appendaged with basal auricles; wings obliquely obovate; keel incurved at apex, obtuse. Vexillary stamen free at base, connate with tube in middle; anthers uniform, 5 basifixed alternating with 5 dorsifixed. Ovary shortly stipitate; ovules 3-21; style incurved; stigma globose, densely penicillate-villous. Legumes oblong, 4-winged lengthwise, septate between seeds. Seeds ovate or oblong-elliptic, with or without aril.
About 10 species: distributed in tropical regions of the Old World; one species (introduced) in China.
(Authors: Wu Delin (吴德邻 Wu Te-lin); Mats Thulin)