Annuals. Stems branched, glabrous. Leaves opposite. Cymes axillary or terminal, paniculate. Flowers 4- or 5-merous. Calyx lobed nearly to base. Corolla rotate, lobes longer than tube. Stamens inserted at throat of corolla tube just below sinus between corolla lobes; anthers cylindric, 2-locular, dehiscing by apical pores. Ovary 2-locular. Capsules 2-valved, many seeded. Seed coat warty.

About 40 species: tropical Africa, tropical and subtropical Asia, Madagascar; two species in China.