Annual herb; branches 30-60 cm long. Leaves 3-7 cm long, larger ones with 6-8 pairs of leaflets and smaller ones with 3-5 pairs; leaflets 4-7 x 2.5-3.5 mm, middle pairs usually longer than the basal and terminal pairs, subsessile, elliptic-oblong, appressed pubescent at the lower side, sparsely pubescent to pubescent on the upper side, sometimes pubescent on the veins only. Flowers 0.5-1.3 cm wide. Sepals 3-5 mm long, ovate-lanceolate, sericeous. Petals 5-7 mm long, pale yellow to yellowish, obovate. Stamens usually 10. Ovary strigose, grooved; style very short or absente. Fruits 8-15 mm across including spines; mericarps with usually 4 spines, sometimes 2 or all reduced to tubercles or absent, crested, glabrous or tubercled, or furnished with spiny tuberculate hairs.