Annual herb, glabrous except for a few simple hairs on the petiolules, lower surface of leaflets, midribs, peduncles and calyces. Leaflets obovate to obovate-cuneate, obtuse, usually retuse and apiculate at the apex, serrate or dentate in the upper third; stipules ovate-oblong, laciniate, the lower side glabrous or with a few hairs along the margins. Inflorescence 2–5-flowered; peduncle usually not protruding beyond the terminal flower. Flowers with pedicels shorter than the calyx tube. Calyx sparingly hairy; teeth ± as long as the tube. Corolla yellow, usually less than twice as long as the calyx; wings longer than the keel. Pod discoid to cylindrical, glabrous, spiny, tuberculate or spineless; coils 1.5–6, turning anticlockwise, loosely appressed to each other, the broadest coil 3.5–8 mm in diameter, hardened at maturity; surface of coils with many radial veins curved, never S-shaped, anastomosing freely before entering the submarginal vein; grooves between dorsal suture and submarginal vein of pod prominent (visible in side view of pod); spines, when present, up to 4 mm long, c. 15 in each row, with 2-rooted base, one root arising in the dorsal suture, the other in the submarginal vein, hooked. Seeds 3 mm long, subreniform, yellowish to yellow-brown, smooth.
