Description from Flora of China
Herbs annual or perennial. Stems caespitose or solitary, prostrate; branches ascending or erect. Leaves linear, linear-subulate, or setaceous, 1- or 3-veined. Inflorescence cymose or flowers solitary. Sepals 5, 1- or 3-veined. Petals 5, white, rarely reddish, apex entire or emarginate. Stamens 10. Ovary 1-loculed; ovules numerous. Styles 3. Capsule narrowly ovoid or ovoid-cylindric, 3-valved. Seeds ovoid, reniform, or discoid; raphe sometimes tuberculate or fimbriate tuberculate.
About 120 species: Arctic regions to the Himalayas, also Chile (one species), Ethiopia, and Mexico; nine species in China.
(Authors: Lu Dequan; John McNeill)