Description from Flora of China
Trees, shrubs, or subshrubs, erect or rarely climbing. Branches usually terete, usually with round or elliptic yellowish glandular lenticels. Leaves simple, opposite, margin entire or 3-5-crenate. Inflorescences terminal trichotomous panicles, leaf opposed cymes, clusters, paniculate corymbs, or spikelike thyrses. Flowers small. Calyx ± cup-shaped or campanulate, truncate, sinuately dentate, or rarely long dentate, teeth equal or clearly 2-lipped. Corolla with a short tube; lobes 4 or obscurely 5, spreading, subequal to clearly 2-lipped. Stamens 4, often didynamous, shorter than corolla or sometimes slightly exserted. Ovary (2- or) 4-locular; ovules 1 (or 2) per locule, pendulous or laterally attached. Style capillary; stigma 2-cleft. Fruit a small drupe, usually with a 4-locular pyrene.
About 200 species: Old World tropics and subtropics, 46 species in China.