Description from Flora of China
Shrubs. Leaves opposite or whorled, simple, margin entire or serrate-dentate. Inflorescences axillary or terminal racemes; bracts small. Calyx 5-veined, 5-dentate, persistent. Corolla 2-lipped, lower lip 3-lobed and largest, upper lip 2-lobed. Stamens 4, short, inserted above middle of cylindric corolla tube, obscurely didynamous. Ovary 8-locular; ovules 1 per locule, pendulous. Style club-shaped; stigma nearly oblique. Drupes equaling or shorter than calyx, with 2-seeded pyrenes.
About 30 species: tropical America, one species introduced to China and sometimes naturalized.