A perennial aquatic herb with thickened base and numerous long, fibrous roots. Leaves long petioled and extremely variable in form and size, sometimes wider than long and obtuse, sometimes linear-lanceolate and acuminate at the apex; the basal lobes of the leaf blades one-quarter to one-half as long as the blade. Flowers monoecious or sometimes dioecious, pediceled and borne near the summits of the scapes in verticels of three, the staminate usually uppermost, each verticel subtended by three bracts. Calyx of three persistent sepals. Stamens numerous; anthers two-celled, dehiscent by lateral slits. Pistillate flowers with numerous distinct ovaries and sometimes with imperfect stamens. The ovaries ripen into a globose or compact head of achenes, each achene broadly winged on both margins, with a beak about one-third its length and horizontal or nearly so.
Common in shallow water almost everywhere and offered by dealers in native plants for colonizing lily ponds and shallow waters. Such situations are scarcely complete without its presence. Flowering from July to September.
Memoir 15 N. Y. State Museum