Herbs, submerged freshwater. Stems short or elongated, erect or stoloniferous. Leaves basal or spirally arranged along stem, sessile, lanceolate or linear, with prominent midvein and several lateral veins, sheathed at base, minutely serrulate along margin. Spathe tubular, sessile or pedunculate, bifid at apex, with longitudinal veins, 1-flowered or sometimes several flowered. Flowers bisexual or unisexual. Sepals 3, persistent, green, linear or lanceolate. Petals 3, white, longer than sepals. Stamens 3-9; filaments slender; anthers 4-thecous. Pistils 3; ovary linear, attenuate into a long, filiform beak; styles 3; ovules numerous. Fruit linear to terete, long, narrow. Seeds numerous, oblong-fusiform, smooth or with spines, sometimes with a filiform projection from each end.

About 11 species: tropical and subtropical regions; five species in China.