Description from Flora of China
Herbs annual, biennial, or perennial, small. Stems often caespitose, procumbent or ascending, slender. Leaves linear or subulate, basally connate; stipules absent. Flower solitary, axillary or terminal, rarely in cymes, small, pedicellate; bracts immediately subtending calyx absent. Sepals 4 or 5. Petals 4 or 5, sometimes absent, white, usually shorter than sepals, rarely equal, margin entire, rarely slightly emarginate. Stamens 4 or 5, sometimes 8 or 10. Ovary 1-loculed; ovules numerous; styles 4 or 5, alternating with sepals. Capsule ovoid to globose, 4- or 5-valved; valves opposite sepals. Seeds numerous, reniform, minute, tuberculate or smooth; embryo curved.
About 30 species: mainly in N temperate regions, a few species in the subtropics; four species in China.
(Authors: Lu Dequan; Richard K. Rabeler)