Herbs, diffusely creeping, villous. Stems slender, much branched, rooting from nodes. Leaves dimorphic. Stem leaves opposite, flat, orbicular. Branch leaves crowded, needlelike, involute. Flowers axillary, solitary. Calyx deeply 5-lobed to base, lobes narrow. Corolla white or rose, actinomorphic; lobes 5, subequal, as long as tube. Stamens 4, included, equal, inserted at base of corolla. Style shorter than or as long as stamens; stigma subulate or 2-lobed. Capsule septicidal lengthwise, valves entire or 2-parted. Seeds numerous; seed coat smooth.

One species: tropical and subtropical Asia.