Description from Flora of China
Trees deciduous. Leaves 1-pinnately compound, opposite; leaflets entire, elliptic or elliptic-lanceolate. Inflorescences cymose-paniculate, terminal. Calyx campanulate, 5-dentate, sometimes unequal. Corolla lobes subequal, rounded or lacerate, tube small, yellow or pale red. Stamens 4, didynamous, included; anthers divergent. Disc cushionlike. Ovary sessile; ovules numerous, in 1 to several rows. Capsule dehiscing loculicidally, terete, slender, 4-angular; septum terete, woody. Seeds inserted in septum, transparent and membranous winged at both ends.
About 15 species: tropical Asia, tropical Africa; three species in China.