Herbs, annual, rarely perennial, not rhizomatous, caulescent; turions absent. Leaves nearly opposite or appearing whorled, submersed, sessile; sheath not persisting longer than blade, not leaving scar when shed, not ligulate, not auriculate or rarely auriculate; intravaginal squamules scales, 2, linear. Inflorescences axillary, solitary flowers or cymes, often subtended by spathe as involucre, sessile or short-pedunculate. Flowers unisexual, staminate and pistillate on same or separate plants; subtending bracts absent; perianth absent; stamens 1; anthers dehiscing irregularly; pollen spheric; pistils 1, not stipitate; ovules basal, anatropous. Fruits achenelike. Seeds 1; embryo straight.
