Herbs, annual [perennial], not rhizomatous, caulescent; turions absent. Leaves alternate, opposite, or pseudowhorled, often all on same plant, submersed, sessile; sheath not persisting longer than blade, not leaving circular scar when shed, ligulate, not auriculate; blade linear; intravaginal squamules scales, 2. Inflorescences axillary, cymes, without subtending spathe, sessile. Flowers uniasexual, staminate and pistillate flowers on same plant; subtending bracts absent; perianth absent. Staminate flowers: stamens 1; anther dehiscing longitudinally; pollen globose. Pistillate flowers: pistils (1--)4--5(--8), distinct, short-stipitate; ovules pendulous, anatropous. Fruits drupaceous. Seeds 1; embryo curved.