Erect annual herb (20)35-50(150) cm tall. Stems sometimes single, glabrous, obscurely to clearly aculeate. Leaves 1.5-6.5(11) cm long; rachis sometimes aculeate; petioles 0.2-0.8(1) cm long; leaflets in (4)6-19(26) pairs, 0.3-1.2(13) cm x 1.5-3.5 mm, oblong, apically obtuse, apiculate, asymmetrical at the base, with a prominent purple to reddish-brown midvein on the undersurface, young leaflets with a few hairs on the margins and midvein below, becoming glabrous; petiolules invested with a few hairs; stipules linear-lanceolate to narrowly triangular, 2-5 mm long with a few obscure marginal hairs. Inflorescence a reduced axillary raceme, 2-6(7) mm long, 1-8(9)-flowered; peduncle 1-2 mm long, glabrous to slightly spreading hairy; pedicels 2-5 mm long, glabrous; bracts 2 mm long, linear to linear-lanceolate, caducous; bracteoles 0.5-0.75 mm long, filiform. Calyx 3-3.5(4) x 3-3.5 mm; tube glabrous with 5 dark brown bands running into the teeth; teeth acuminate, 1-1.75 mm long, obscurely hairy on the margins. Standard yellow with strong purple veining on the outer face, rarely pure yellow, 1-1.3 x 1-1.1 cm, rounded, apically emarginate, without appendages; wings yellow, (0.95)1.1-1.2(1.25) cm x 3.5-4 mm, with an upper basal tooth and with lamellate sculpturing in the upper basal section on outer face; keel yellow, slightly striped purple or brownish on the beak, (1)1.2(1.35) cm x (5)7 mm, the limb subtriangular with a basal tooth pointing ± upwards. Ovary and style glabrous. Pod (4.5)8-9.5(10.5) cm x 2-3(4) mm, linear to slightly falcate, acuminate, held erect, glabrous, (4)12-17(18)-seeded; septa 5-6 mm apart; valves with prominent raised venation and occasional small scattered prickles (visible with a x10 lens). Seeds olive-green with fine black speckling or brownish, 3.5-4 x 1-1.5 mm, 1.5-2 mm thick; small hilum in central circular pit.
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