Description from Flora of China
Herbs, subshrubs, shrubs, or rarely small trees, pubescent with stellate, simple, bifurcate or glandular hairs. Leaves simple, irregularly crenate-serrate, foliar nectaries lacking. Inflorescence an axillary or terminal cyme, sometimes congested; bracts conspicuous, persistent. Flowers bisexual, distylous or homostylous. Calyx campanulate, 5-lobed, persistent, sometimes accrescent. Petals 5, flat, not cucullate, without appendages, base clawed, free or shortly adnate to base of staminal tube, purple, yellow, orange, or white (sometimes with a yellow throat), persistent. Stamens 5, opposite to petals; filaments united into a staminal tube; anthers 2-thecate, extrorse, thecae parallel; staminodes absent. Ovary syncarpous, 5-celled, sessile or shortly stipitate; ovules (1 or)2 per locule; styles 5, free or basally connate; stigma slightly thickened. Capsule 5-valved, depressed globose or pyramidal and 5-winged, loculicidally or septicidally dehiscent (or both), often surrounded by persistent calyx and persistent withered corolla. Seeds 1 per cell, obovoid; cotyledons flat.
Between 50 and 60 species: primarily tropical and subtropical with centers of diversity in Malaysia and Pacific islands, and Central and South America; some species now pantropical weeds; one species in China.