Herbs small, usually several in a cluster. Stems short, unbranched. Inflorescences racemose or spicate; bractlets present or absent. Calyx tubular, apex 4- or 5-lobed; lobes usually unequal. Corolla white, pale purple (yellow, purple-red, or rose-red), tubular (tubular-campanulate or funnelform), apex 5-lobed. Stamens 4, included, or slightly exserted; anther cells 1 fertile and 1 absent or reduced into a spur, rarely both fertile. Ovary 1-locular and 2 placentas parietal (or 2-locular and placentas axile). Stigma lobed. Capsule ovoid or subglobose, dehiscing loculicidally. Seeds numerous, some reduced; testa reticulate.

About 16 species: tropical Asia; one species in China.