四棱豆 si leng dou

Dolichos tetragonolobus Linnaeus, Syst. Nat., ed. 10, 2: 1162. 1759; Botor tetragonolobus (Linnaeus) Kuntze.

Herbs, annual or perennial, climbing, with tubers. Stems 2-3 m or more, glabrous. Stipules dorsifixed, ovate to lanceo­late, 0.8-1.2 cm; petiole sulcate; leaflets ovate-deltoid, 4-15 × 3.5-12 cm, base truncate or rounded, apex acute or acuminate. Racemes axillary, 1-10 cm, 2-12-flowered; peduncles 5-15 cm; bracteoles suborbicular, 2.5-4.5 mm in diam. Calyx campanulate, ca. 1.5 cm. Standard green outside, pale blue inside, ca. 3.5 cm in diam., base appendaged, apex emarginate; wings pale blue, ca. 3 cm, with T-shaped auricle at middle of claw; keel white tinged with pale blue, slightly incurved with rounded auricle at base. Legumes yellow-green or green, sometimes with red spots, tetragonal, 10-25(-40) × 2-3.5 cm, wings 0.3-1 cm wide with serrate margins. Seeds 8-17, white, yellow, brown, black, or variegated, subglobose, 0.6-1 cm in diam., shining, margin arillate. Fr. Oct-Nov.

Cultivated. Guangdong, Guangxi, Hainan, Taiwan, Yunnan [native perhaps to tropical Asia; cultivated throughout the tropics].

This species is used for food; parts are eaten as vegetables.