Aquatic perennial herbs, with rootstocks, mucilage-coated stems, floating or immersed leaves, and solitary axillary flowers. Sepals 3, rarely 4. Petals 3, rarely 4. Stamens 3-18; anthers extrorse, the connective continuous with the filament. Carpels 2-18, distinct. Stigmas sessile or nearly so; ovules 2 or 3, orthotropous. Fruits indehiscent, coriaceous, separate. Seeds 1-3, borne on the dorsal suture; embryo at the base of fleshy endosperm; cotyledons fleshy; hypocotyl very short.

Two genera and about 5 species, widely distributed in fresh-water lakes and streams.

Leaves dissected, excepting the small floating ones; stamens 3-6.



Leaves peltate, entire, floating; stamens 12-18.