Aquatic, usually large, perennial herbs with milky latex and stout creeping rhizome bearing roots at the nodes. Leaves alternate, peltate, floating on the water surface when immature, raised high above the water surface when mature, petiole very long upto 2 m, bearing numerous spines, lamina usually reniform to orbicular, glaucous with upturned margin, prominently veined from the centre. Flowers large, pinkish red, white or yellow. Perianth segments 14 to 30; outer 2-5 persistent and sepal-like, often regarded as sepals; inner caduceus. Stamens numerous (many senate), caducous, usually with conspicuous fleshy appendages. Pollen tricolpate, carpels several, borne singly in the cavities of the broad, turbinate, spongy receptacle; stigma terminal, ± peltate. Fruit a hard walled nut.