Rhizomes slender, long-creeping; culms rather distant, 50-100 cm. long, acutely 3-angled, 2-7 mm. thick at base; basal sheaths 3-angled, with short blades 0.5 cm. long; inflorescence pseudolateral, umbelliform with a few rays, or capitate; bract 1, continuous with the culm, 3-angled, 2-5 cm. long; spikelets oblong to ovate, 7-17 mm. long, 5-7 mm. thick, obtuse, ferrugineous, in clusters of 2 or 3; scales oblong, about 4 mm. long, hyaline, dark brown striate，ciliate, shal­lowly bifid, the midrib excurrent into a short, erect mucro; achenes broadly obovate, biconvex, 2-2.5 mm. long, nearly smooth, lustrous; bristles 3-5, nearly as long as the achene, retrorsely scabrous; stigmas 2. July-Oct. Marshy places and shallow ponds.

Hokkaido, Honshu, Shikoku, Kyushu; common. Ussuri, Korea, Manchuria, China, Ryukyus, Ma­laysia, India, and s. Europe.