琉球豇豆 liu qiu jiang dou

Phaseolus riukiuensis Ohwi, J. Jap. Bot. 13: 437. 1937; Azukia riukiuensis (Ohwi) Ohwi.

Twining herbs, strigose. Stipules peltate, ovate, 4-6 mm, strigose, 5-7-veined; terminal leaflet obovate or elliptic, 2-4 × 1.2-2 cm, sparsely strigose, base cuneate or obtuse, margin en­tire, apex slightly acute and mucronate; lateral leaflets obliquely ovate, subequal. Racemes axillary, 5-8-flowered; peduncles 3-10 cm. Calyx obconic, ca. 2.5 mm. Corolla yellow; standard or­bicular, ca. 1.2 cm wide, apex emarginate, with rectangular cal­losity at middle, auricles reflexed, incurved; wings obovate, ca. 1 cm, with reflexed appendage at base; keel incurved. Ovary linear, sparsely strigose. Legumes brown with white striations, subcompressed, 3.5-4.5 × ca. 0.4 cm, glabrous. Seeds dull red, elliptic, ca. 3 mm; hilum white.

Taiwan [Japan (Ryukyu Islands)].

The authors have not seen any material of this species from China, and it was not mentioned in Fl. Taiwan (ed. 2, 3. 1993). However, Vigna riukiuensis has been recorded from Taiwan (e.g., in Tomooka et al., Genet. Res. Crop Evol. 49: 521-530. 2002). The closely related V. nakashimae (Ohwi) Ohwi & H. Ohashi (J. Jap. Bot. 44: 30. 1969; Phaseolus nakashimae Ohwi, J. Jap. Bot. 13: 436. 1937), described from Japan, with smaller and more pale yellow flowers, has also been recorded but from mainland China.