Herbs perennial, aquatic. Rhizomes branched, repent, forming swollen terminal storage tubers late in growing season. Leaves arising from rhizome, alternate, emersed or floating, long petiolate; leaf blade centrally peltate, veins radially extended. Flowers solitary, axillary, long pedunculate, bisexual, hypogynous, actinomorphic, entomophilous, borne above water surface. Tepals numerous, distinct, outermost reduced, inner ones larger and petaloid. Stamens numerous; anthers dehiscent by longitudinal slits. Pistils numerous, simple, separately and loosely embedded in cavities on flattened top of receptacle. Ovary 1-loculed; ovule 1, pendulous; styles very short; stigmas capitate. Fruit nutlike, indehiscent. Seeds without endosperm and perisperm; embryo large; cotyledons 2, fleshy.
Herbs , perennial, aquatic, rhizomatous; roots adventitious; air chambers conspicuous in vegetative portions of plant. Rhizomes branched, repent, slender, terminal portions becoming tuberous-thickened late in growing season. Leaves arising directly from rhizome, alternate, floating or emersed; petiole long. Leaf blade peltate, orbiculate, margins entire; laticifers present. Inflorescences axillary, solitary flowers. Flowers bisexual, protogynous, diurnal, borne above water surface; peduncle long; involucre absent; perianth not persistent in fruit (outermost tepals of N . lutea normally persistent), hypogynous; tepals numerous, distinct, outermost reduced, inner tepals becoming larger and more petaloid; stamens numerous; filaments slender; anthers dehiscing by longitudinal slits, connective appendage incurved; pistils numerous, 1-carpellate, separately embedded in flattened top of turbinate receptacle; ovary 1-locular; placentation apical; ovule 1; style short; stigma nearly sessile, capitate. Fruits nutlike, indehiscent, loose in cavities of strongly accrescent receptacle. Seed 1, aril absent; endosperm and perisperm absent; embryo completely filling seed; cotyledons 2, fleshy.