A much-branched annual herb, 1-2.5 m tall. Stems glabrous, usually sparsely aculeate. Leaves 3.5-20 cm long; rachis glabrous, occasionally aculeate; petioles 0.3-1.7 cm long; leaflets in 8-41 pairs, 4-16 x 1.75-4.5 mm, oblong, apiculate, slightly broader and asymmetrical at the base, glabrous; stipules 3-7 mm long, narrowly triangular to lanceolate, caducous to ± persistent. Racemes 0.3-3.5(9) cm long, (1)2-8(17)-flowered; peduncle 0.1-0.9(1.8) cm long, glabrous; pedicels 0.3-1.5 cm long, glabrous; bracts 2-3 mm long, linear-lanceolate, caducous; bracteoles 1-2 mm long, linear, located slightly below the hypanthium, caducous. Calyx 3-4.5 x 3-4 mm, the tube glabrous with 5 vertical dark brown bands each running into a tooth; teeth 0.5-0.75 mm long and well-spaced often giving the calyx a ± truncate appearance, acuminate, woolly at the margins. Standard yellow finely speckled brown or purplish, 1.1-1.4 x 1-1.3 cm, the blade wider than long, suborbicular, apically emarginate, basally rounded, truncate or slightly cordate, the appendages small, triangular, divergent and without free tips; wings 1.1-1.4 cm x 3-5.5 mm, with a 1 mm long upper basal, finely acuminate ± upward-pointing tooth and with open lamellate sculpturing in the upper basal section; keel 1-1.3 cm x 5-7 mm, the limb with an erect basal tooth 0.3-0.5 mm long and a secondary widely triangular tooth above it. Ovary 15-26(32)-ovulate, glabrous; style glabrous. Pod (2.4)7.2-11.5 (rarely 13.5) cm x (2)2.5-3(5.5) mm, erect, moniliform, shortly stipitate and beaked, (2)8-18(rarely 26)-seeded; septa 5-6 mm apart; sutures 1.5 mm wide, purplish-green, distinctly darker than the valves which, particularly when immature, have a secondary sutural ridge. Seeds brown or blackish, 2-3.3 x 2 mm, 1.5-2 mm thick, ellipsoid or ± spherical with a subcentral hilum in a very small circular pit.
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