Description from Flora of China
Twining or erect herbs, rarely subshrubs. Leaves pinnately 3-foliolate; stipules peltate or basally spurred, 2-lobed, cordate, or truncate. Racemes axillary or terminal, nodes of rachis often thickened and glandular. Bracts and bracteoles deciduous. Calyx 5-toothed, 2-lipped. Corolla yellow, blue, or purple; standard suborbicular, base appendaged; wings shorter than standard; keel subequal to wings, incurved, not beaked or produced into an incurved or spirally twisted beak. Stamens diadelphous; anthers uniform. Ovary sessile; style filiform, upper part thickened, bearded or hirsute lengthwise inside; stigma oblique. Legumes linear or linear-oblong, terete or flat. Seeds reniform or subquadrate; hilum short or elongate, with or without aril.
According to molecular evidence (Thulin et al., Syst. Bot. 29: 903-920. 2004), Vigna adenantha belongs to a group of neotropical species of Vigna that is not closely related to the Old World species otherwise present in China. Pending a new classification of the New World species, V. adenantha is here retained in Vigna.
Phaseolus anguinus Bunge (Enum. Pl. Chin. Bor. 20. 1833), described from near Beijing, is probably a species of Vigna. No type material has been seen, but the name may well be a synonym of V. radiata.
About 100 species: distributed in tropical regions; 14 species (one introduced) in China.
(Authors: Wu Delin (吴德邻 Wu Te-lin); Mats Thulin)