13. Vigna angularis (Willdenow) Ohwi & H. Ohashi, J. Jap. Bot. 44: 29. 1969.
赤豆 chi dou
Dolichos angularis Willdenow, Sp. Pl. 3: 1051. 1800; Azukia angularis (Willdenow) Ohwi; Phaseolus angularis (Willdenow) W. Wight; P. nipponensis Ohwi; Vigna angularis var. nipponensis (Ohwi) Ohwi & H. Ohashi.
Annual herbs, erect or twining, 30-90 cm tall. Stems angular, sparsely pilose. Stipules peltate, lanceolate, ca. 8 mm, point of attachment elongated; leaflets ovate or rhomboid-ovate, 5-10 × 5-8 cm, sparsely pilose on both surfaces, apex broadly triangular or subrounded, lateral leaflets oblique, entire or shallowly 3-lobed. Racemes axillary, 5- or 6-flowered, pedunculate. Calyx campanulate, 3-4 mm. Corolla yellow, ca. 15 mm; standard oblate or subreniform, apex emarginate; wings broader than keel, shortly clawed and auriculate; keel apex incurved for nearly a half circle, base clawed. Ovary linear; style curved. Legumes terete, 5-8 × 0.5-0.6 cm, glabrous or almost so. Seeds dull red or with various other colors, oblong, 5-6 × 4-5 mm, truncate or subrounded at both ends; hilum not impressed. Fl. Jun-Jul, fr. Sep-Oct.
Widely cultivated and also wild in China [native to Asia; introduced in America, Africa, and elsewhere].
This species is edible and is used medicinally.