Herbs, perennial, sometimes prostrate or floating, unarmed. Leaves bipinnate, sensitive to touch; stipules obliquely cordate, membranous; rachis with or without glands; pinnae not glandular; leaflets opposite, several to numerous pairs, small. Heads solitary, ovoid-globose, pedunculate, with bisexual flowers in distal part and sterile flowers with elongate staminodes at base. Calyx cam­panulate, shortly 5-dentate. Petals 5, free or fused at base. Stamens 10, rarely 5, free; anthers with or without a small gland at apex. Staminodes 10, petaloid and elongate in neuter flowers. Ovary stipitate; ovules numerous; style filiform; stigma concave. Legume deflexed from stipe, oblong, plano-compressed, subseptate between seeds or rarely 1-seeded. Seeds transverse, ovoid, compressed, funicle filiform.

Eleven species: tropical and subtropical regions, especially in Australia and the Americas; one species (introduced) in China.