Erect, annual herb, 20-40 cm tall, branched. Stems glabrous or very sparsely glandular-puberulous when young. Leaves 3-foliolate, petiolate; petioles up to 6 cm long, glabrous; leaflets linear to narrowly lanceolate, 1-6-5 cm long, 0-5-2-5 mm broad (often broader in tropical Africa), acuminate at the apex, cuneate at the base, sparsely and minutely asperulous at least on the margins. Inflorescence a relatively dense, terminal raceme, rapidly elongating in fruit; bracts simple, linear, 1 mm long, caducous; pedicels shorter than the gynophore, slender, up to 4 mm long, glandular-puberulous. Sepals linear-subulate, unequal, 4-8 mm long, glabrous or sparsely setulose on keel and margins. Petals oblong-spathulate, 8-14 mm long, 1-5-2-5 mm broad, apex obtuse, tapering into a basal claw almost as long as the lamina, mauve, the two upper ones usually with a bright yellow median spot surrounded by a dark purple line. Stamens 6-12, all fertile though some have smaller anthers; filaments slender, the longer eve
