Herbs, perennial, cespitose or matted, often decumbent, rooting at proximal nodes or floating, 0.3--5 dm. Culms erect, decumbent and rooting at nodes, or floating, terete, 1--2 mm diam., smooth. Cataphylls 0 or 1--2, straw-colored, apex acute. Leaves: basal 1--3, cauline 1--4; auricles 0.8--2.1 mm, apex rounded to acute, membranaceous; blade terete, 3.7--15 cm x 0.4--1.3 mm, occasionally with filiform, flaccid, and floating leaves to 60 cm. Inflorescences terminal racemes of 2--9 heads, 2--10 cm, branches erect; primary bract erect; heads 2--12-flowered, obconic or rarely hemispheric, 4--13 mm diam. Flowers: tepals light brown or greenish to reddish brown, linear to narrowly lanceolate, apex acute to acuminate-subulate; outer tepals (2.1--)2.8--4.9 mm; inner tepals (2.1--)2.8--5.5 mm; stamens 3 or 6, anthers 1/2--3/4 filament length. Capsules usually exserted, dark brown, 1-locular, ovoid to oblong, (3.2--)3.5--6.1 mm, apex acute to acuminate proximal to beak, valves separating at dehiscence. Seeds narrowly obovoid to obovoid, 0.6--0.7 mm, not tailed; body clear yellow-brown.. n = ca. 30, ca. 50--60, 2n = ca. 112.
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