Description from Flora of China
Herbs, aquatic or of marshes, usually with a tuber. Leaves aerial, floating, or submerged, all basal, petiolate, margin entire. Inflorescences paniculate or occasionally umbellate; branches whorled, each one usually secondarily branched and with bracts at base. Flowers bisexual. Petals usually larger than sepals. Stamens 6. Carpels numerous in a single whorl, free, each with 1 ovule. Achene laterally compressed, 1- or 2-grooved or canaliculate abaxially, with a usually adaxial beak.
About 11 species: temperate and subtropical regions; six species (one endemic) in China.