Rhizomes absent. Cauline stems terete, without spots, 27--95 cm; glands white, green, greenish brown, or gold, to 0.3 mm diam. Turions terminal or lateral, common, 2.5--4.8 cm ´ 0.8--2.2 mm, soft; leaves ± 2-ranked, flattened with outer and inner leaves in same plane; outer leaves 3--4 per side, base not corrugate, or rarely corrugate, apex acute; inner leaves undifferentiated. Leaves submersed, ± spirally arranged, rigid, sessile; stipules disintegrating, inconspicuous, connate, free from blade, white, not ligulate, 0.6--1.6 cm, fibrous, shredding at tip, apex obtuse; blade green to olive-green, linear, not arcuate, 1.2--6.3 cm ´ 0.6--2 mm, base slightly tapering, without basal lobes, not clasping, margins entire, not crispate, apex not hoodlike, acute to nearly bristle-tipped, rarely obtuse to apiculate, lacunae absent; veins 3--5(--7). Inflorescences unbranched, emersed; peduncles not dimorphic, terminal, erect, rarely recurved, cylindric, rarely slightly clavate, 1--4.5 cm; spike not dimorphic, cylindric, 0.6--1.3 cm. Fruits sessile, green-brown, ovoid, turgid, not abaxially or laterally keeled, 1.9--2.1 ´ 1.3--1.8 mm; beak erect, 0.5--0.8 mm; sides without basal tubercles; embryo with 1 full spiral. 2n = 26.
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Stems very slender; to 1 m, branched above, commonly with paired glands at the nodes; rhizome scarcely developed; lvs all submersed, linear, rather stiff, 2–6 cm × 0.5–2 mm, acute or attenuate or often bristle-tipped, with bold, vein-like margins, 3–5(7)-veined, the lateral veins very delicate, the midvein not bordered by lacunae or with 1 row on each side in the basal third only; stipular sheaths axillary, free, white, 7–15 mm, closed at base when young, becoming conspicuously fibrous in age; winter-buds commonly produced, flattened, the outer lvs divergent, arcuate, inrolled; peduncles mostly terminal, very slender, usually 3–4 cm, not thickened distally; spike slender,10–15 mm, with 3 or 4 remote whorls of fls; frs obovoid, 2–3 mm, not keeled; 2n=52. Alkaline ponds and streams; Que. to Mack., s. to Conn., N.Y., O., n. Ind., Minn., and Utah. (P. rutilus, misapplied)
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