Rhizomes present. Cauline stems terete, conspicuously spotted, 8--95 cm; nodal glands absent. Turions absent. Leaves both submersed and floating, ± spirally arranged. Submersed leaves petiolate, lax; stipules deliquescent, inconspicuous, convolute, free from blade, light to dark brown, not ligulate, 0.7--1.2 cm, not fibrous, not shredding at tip, apex obtuse; petioles 0.5--4.5 cm; blade dark green, linear-lanceolate to lanceolate, often arcuate, 3.5--13.8 cm ´ 60--165 mm acute, base acute to rounded, without basal lobes, margins entire, crispate, apex not hoodlike, acute to obtuse, lacunae in 2--5 rows each side of midrib; veins 7--19. Floating leaves: petioles continuous in color to apex, 1--16.5 cm; blade adaxially light to dark green, lanceolate to round-ovate, 2.5--8.5 cm ´ 11--44 mm, base rounded to cordate, apex acute to rounded; veins 15--21. Inflorescences unbranched, emersed; peduncles not dimorphic, terminal or axillary, erect to ascending, cylindric, 3.3--9.4 cm; spikes not dimorphic, cylindric, 17--36 mm. Fruits sessile, dark green to dark brown, ovoid to obovoid, turgid, abaxially keeled, laterally ridged, 5--6.5 ´ 4.1--5 mm, lateral ridges without points; beak erect, 0.5 mm; embryo with 1 full spiral. Chromosome number apparently unknown not available.
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Stems rarely over 5 dm, simple, black-spotted; submersed lvs narrowly lanceolate, undulate-margined, 8–15 × 1–3 cm, 9–19-veined, long-acuminate, tapering at base to a poorly defined petiole; floating lvs broadly elliptic or oval, 4–8 × 2–5 cm, many-veined, obtuse, the base broadly obtuse to subcordate; petioles stout, black-spotted, 2–8 cm; stipules axillary, free, to 6 cm, cuspidate to long-acuminate; peduncles 5–12 cm, somewhat thicker than the stem; spike dense, cylindric, 2–4 cm; frs obliquely obovoid, 3.5–4.5 mm (beak included), with flat sides and 3 low, sharp dorsal keels. Shallow, acid waters and muddy shores; s. Me. to Fla. and Ala., chiefly near the coast; s. Ind. to Mo. and Ark. Shore-forms may lack lvs of the submersed type.
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