Herbs, annual, slender and weak, erect or sometimes decumbent, succulent. Leaves opposite, succulent, sometimes scalelike. Flowers axillary, solitary. Bracteoles absent. Corolla tube much longer than calyx, distally inflated; limbs 2-lipped; lower lip 3-lobed; upper lip 2-lobed, conspicuously shorter than lower lip. Stamens 2, inserted on upper side of corolla tube; filaments filiform; anther locules distinct, equal, parallel; staminodes 2, small, inserted on anterior side, margin entire. Style short; stigma 2-lamellate, clavate, or capitate. Ovary 2-loculed; ovules numerous in each locule. Capsule loculicidal; valves entire or apex shallowly 2-lobed. Seeds small, numerous.

About 10 species: tropics of Africa, Asia, Australia, and Oceania; one species in China.