Description from Flora of China
Trees. Leaves opposite, 1-3-pinnately compound; leaflets entire, petiolate. Inflorescences paniculate or reduced almost to fascicles, terminal or lateral; bracts and bractlets linear or leaflike. Calyx campanulate, apex 5-lobed or truncate. Corolla funnelform-campanulate or salverform; tube short or long, limb slightly bilabiate; lobes rounded, spreading. Stamens 4(or 5), didynamous or subequal; staminode usually present. Disc annular, slightly fleshy. Ovary terete; ovules numerous, 2-rowed in each locule. Style included; stigma ligulate, 2-lobed. Capsule dehiscing loculicidally, long, terete, 2-angular; septum compressed, woody. Seeds compressed, transparent membranous winged at both ends.
About 16 species: tropical Asia; seven species in China.