形态特征：Twining herbs, 2–3 m. Stem slender, terete, multi-branched, sparsely pubescent when young, glabrescent. Leaves trifoliolate; stipules and stipels subulate to setaceous, 0.5–1.7 mm, persistent; petioles 3.4–5.2 cm; leaflets membranous to thin chartaceous, nearly glabrous on both surfaces, light green adaxially, glaucous abaxially, blunt and mucronate at apex, subrounded to broadly cuneate at base, secondary veins 4–6 pairs, reticulate veins obvious on both surfaces; terminal leaflet ovate, elliptic or ovate oblong, 2.5–4.8 × 1.8–3.7 cm; lateral ones smaller, oblique, 1.7–4 × 1–2.7 cm; petiolules 1–3 mm. Pseudoracemes axillary, 5.5–16 cm, with repand wings at base of peduncles, 9–16-flowered; wings 3.2–3.7 cm × 1–4 mm; bracts and bracteoles setaceous or subulate, 0.5–1.2 mm, minute. Calyx tubular, grass green, 5–7 × 3.5–4 mm, longitudinal veined, obliquely truncate at the calyx mouth, gibbose at the base. Corolla light yellow. Standard obovate, 18 × 8 mm, apex emarginate, auriculate, attenuate to a short claw at base; wing petals falcate, 15 × 2.5 mm, apex rounded, attenuate to a 10 mm claw; keels nearly subequal as the wing petals, with a 5.5 mm-blade and 11 mm-claw. Stamens 10, diadelphous, 15–17 mm. Ovary linear, with a slender stipe surrounded by a basal disc; style dilated at the bending part; stigma capitate and hairy. Pods moniliform, glabrous, acuminate at apex, attenuate at base, 4–5-seeded, conspicuously constricted between the seeds, valves thin leathery. Seeds subglobose and dorsoventrally compressed, ca. 6 × 6 × 3 mm, bluish black, hilum raised, ca. 3 mm long.
