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Stems branched. Leaves with the lower in whorls of 3, linear to linear-lanceo-late, sometimes obovate, the lowest sometimes alternate, 5-14 mm long and 1-1.5 mm wide, the middle and upper in whorls of 3-8, linear-lanceolate, acute, serrate, 10-25(-40) mm long and 1-2 mm wide; squamulae intravaginales 2, axillary, oblong, membranous, transparent, fringed, to 0.5 mm long. Staminate spathe solitary in the leaf-axil, 1.25-1.5 mm high, tearing open when the flower is released; pedicel 1-2 mm long; sepals white, often-tinged with red, 1.5-3 mm long and 1 mm wide; petals white, often tinged with red, 2-3 mm long and 0.5 mm wide, falling before the sepals; stamens with slender, short filaments and linear anthers. Carpellate spathe ca. 5 mm long; sepals white, sometimes with red dots, 1.5-3 mm long and 0.75 mm wide, petals white, 1.5-3 mm long and 0.3-0.5 mm long; hypanthium 1.5-10 cm long; ovary 3-4 mm long, the styles 0.8-1 mm long. Fruits elongate, with a constriction between each pair of seeds, 4-7 mm long, surrounded basally by the remnants of the spathal bracts and bearing the remnant of the hypanthium (1.5-3 cm long) apically; seeds 2-6, in a row, cylindrical, oblong, apiculate at one side, 2-3 mm long, the testa smooth, dark brown.
Submerged, perennial, attached aquatic, branched, with stems to 2 m long, usually forming a canopy immediately below water surface; internodes to 5 cm long in deeper water, much closer together near surface. Leaves in whorls of 3–8, to 4 cm long and 5 mm wide, with finely toothed margins. Perianth segments 1–3 mm long. Male flowers 1 per spathe, without hypanthium, released as a mature globose bud from spathe; spathe subsessile, 1.5–3 mm long. Female flowers mostly 1, sometimes 2, per spathe; hypanthium slender, 1.5–10 cm long; spathe sessile, c. 5 mm long. Fruit ±7 mm long, 1.5 mm diam. Seeds 2–3 mm long.
Leaves in whorls of 3-8, linear or narrowly strap-shaped, 0.7-1.7 cm × 1-4 mm, midvein distinct, margin conspicuously denticulate, apex acute. Male spathe green; sepals white, ca. 2.3 × 0.7 mm; petals reflexed, white or reddish, ca. 2 × 0.5 mm. Female spathe green; flowers similar to male ones. Fruit with 2-9 spinelike projections or smooth and without projections. Seeds (1 or)2-6. Fl. and fr. May-Oct. 2n = 16, 24.
Plants producing small tubers; lvs up to 20(–40) × 2(–5) mm, denticulate; stipules fringed with orange-brown hairs; staminate fls breaking loose as in Elodea nuttallii; sep 1.5–3 mm; pet narrower, transparent, with a few red streaks; 2n=16 (diploid), 24 (triploid). Rivers, lakes, and ponds; intr. in se. U.S. and spreading n. near the coast to Va., Md., D.C., and Del., locally abundant. June–Aug.
Rhizomes and erect stems with turions; subterranean turions cream-brown, appearing as tubers, surface smooth; turions from erect stems olive-green, covered with short, stiff scales. Leaves 8--15(--20) ´ 1.2--4 mm, margins serrulate. Inflorescences: spathe of 2 connate bracts. Flowers 1 per spathe; staminate pedicels 0.5 mm; pistillate flowers with floral tube 10--50 mm; ovary 1-locular. 2n = 32.
A plant which grows under water. The stem is much branched. It is 15-30 cm long. The leaves are carried in rings. They are light green and sword shaped. They are 1-2 cm long by 0.2-0.5 cm wide. The leaves have fine teeth along the edge. These teeth allow light through. The leaves can have reddish-brown dashes. It develops white corms on the stolons in the soil.
