1. Cyamopsis tetragonoloba (Linnaeus) Taubert in Engler & Prantl, Nat. Pflanzenfam. 3(3): 259. 1894.
瓜儿豆 gua er dou
Psoralea tetragonoloba Linnaeus, Mant. Pl. 1: 104. 1767; Cyamopsis psoraloides Candolle, nom. illeg. superfl.
Herbs, 0.6-1.3 m tall. Stems erect, branched, almost glabrous, base woody; branches conspicuously 4-angled. Stipules linear, 5-8(-10) mm. Leaves 3-foliolate; petiole 0.8-4 cm; leaflet blades ovate to subrhombic, 3-7 × 1.5-4 cm, abaxially with appressed grayish medifixed trichomes, adaxially sparsely appressed hairy or almost glabrous, base cuneate to broadly cuneate, margin dentate to crenate, apex obtuse to acute. Racemes 4-10 cm, 6-30-flowered; peduncle 3-5 mm. Calyx 3-4.5 mm, outside hairy; teeth triangular, 2-2.5 mm, but most abaxial one longer than calyx tube. Corolla pink, 4-5.5 mm; standard broadly ovate, claw short, apex obtuse; keel pocketed at side, spur absent. Stamens 2.5-4.5 mm. Ovary glabrous. Legume nearly linear, 4-7 cm × 3-8 mm, erect, longitudinally ridged, with septa between seeds. Seeds 6-12 per legume, black to grayish, surface tuberculate. 2n = 14, 16.
Cultivated in W Yunnan [probably native to NW India].
This species is cultivated for the gum from its seeds (guar gum), which is used as a stabilizer in processed food.