Glabrous, floating. Rhizome long, 1/8 in. in diam. Stems tufted, 1–2 1/2 ft. long, at the top 1/25 in. in diam., round trigonous. Leaves 0; leaf-sheaths pale-brown or reddish, the uppermost produced on one side 0– 1/2 in. but hardly green. Head 1, of 1–12 sessile spikelets; bracts 1–3, lowest often suberect, shorter than the head, as though a continuation of the stem. Spikelets 1/2–1 by 1/6– 1/5 in. (rarely up to 1/4 in. broad), much flattened, 30–40-flowered, sometimes 70-flowered, pallid or reddish. Glumes very closely packed, ovate, boat-shaped, apiculate, 3–5-nerved, sometimes scabrous on the upper part of the keel, falling seriatim from the lowest fertile glume; rhachilla persistent. Stamens 3; filaments broad; anther-cells thick, muticous. Style long, linear; branches 3, linear, very short. Nut 2/3 the length of glume, ovoid, flattened, long acuminate; base of the nut, especially the margins, corky thickened.
