Description from Flora of China 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.