Description from Flora of China
Herbs, floating. Stems short, stoloniferous. Leaves basal, floating or submerged, rarely emerged, petiolate and stipulate; blade ovate, orbicular, or reniform, entire, with more than 5 curved veins, sometimes with a central pad of spongy tissue on abaxial surface of floating blade. Plants monoecious; flowers unisexual. Spathes 1- or 2-valved, male spathes pedunculate, 1-6-flowered; female spathes sessile, 1-flowered. Sepals greenish white. Petals white or yellowish, much larger than sepals. Stamens 6-12; anthers 2-thecous. Ovary elliptic; ovules numerous; styles 6, bifid. Fruit with 6 ribs, irregularly dehiscent at apex. Seeds ellipsoid.
About three species: Africa, Asia, Australia, Europe, North America; one species in China.