Herbs annual or short-lived perennial. Rhizomes erect, unbranched. Leaves submerged or floating; leaf blade broadly elliptic to orbicular, venation primarily radiate, juvenile ones with basal sinus, mature ones lacking sinus and only slightly indented basally, margin entire, centrally peltate. Flower epigynous, floating or often partially or entirely submerged, cleistogamous or perianth spreading. Sepals 4, greenish, not petaloid, persistent. Petals numerous, in ca. 5 series, showy, transition to stamens gradual. Stamens shorter than sepals and petals, inserted at apex of ovary; filament linear; anther connective unappendaged. Carpels 7--16, completely united. Style absent. Stigma sessile and radiate on cup-shaped stigmatic disc, lacking marginal appendages. Fruit irregularly dehiscent. Seeds smooth, arillate.

One species: E Asia.