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Herbs: rhizomes present; turions absent; tubers absent or present. Stems terete, nodes without oil glands. Leaves submersed, alternate, opaque, sessile, linear, channeled, turgid, acute at base acute, margins entire, apex obtuse to acute, veins 1--5; stipules not tubular, adnate to base of leaf blades for 2/3 or more length of stipule, extending past adnation as free ligule. Inflorescences spikes, capitate or cylindric, submersed; peduncles flexible, not projecting inflorescence above surface of water. Flowers: pistils 4. Fruits abaxially rounded, beaked or not, turgid; embryo with less than 1 full coil. x = 13.
Aquatic perennial herbs, often rhizomatous. Stems terete; turions absent. Leaves submerged, alternate, simple, opaque, sessile, linear, canaliculate, turgid; base acute; margins entire; apex subulate to obtuse. Stipules tubular, sheathing stem and young inflorescences, connate or convolute, adnate to base of blade for at least 60% of stipule length. Inflorescence a capitate or cylindric spike with 1–20 whorls of flowers, with 2–4 flowers in each whorl, submerged; peduncles flexible. Fruit abaxially rounded, beaked; embryo with less than one full coil.
