Trees or shrubs, evergreen, unarmed. Leaves bipinnate; stipules deciduous, small, setaceous; petiole often glandular; leaflets opposite, numerous and small, or few and larger, oblique. Heads solitary or fasciculate, axillary, globose, pedunculate; bracts usually 2. Flowers sessile, usually bisexual. Calyx campanulate, 5-toothed. Petals 5, free or nearly so. Stamens 10, free, exserted; anthers apically eglandular. Ovary stipitate; ovules numerous; style filiform. Legume stipitate, broadly linear, plano-compressed, leathery, 2-valved, continuous within. Seeds transverse, ovoid, flat.

About 22 species: native to the Americas, one species introduced and naturalized in the Old World including China.