Japan Flora: Annual or short­ lived perennial; culms tufted, 10-60 cm. long, compressed- tetraquetrous, surrounded at base by a bladeless sheath; leaves laterally compressed, distichous, 的ft, 1.5-2.5 mm. wide, long- attenuate, the sheath keeled, strongly compressed; inflorescence compound to decompound, loose to rather dense, the bracts 2-4, short, setaceous; spikelets ovoid-globular to globular, 2.5-4 mm. long, 1.5-2 mm. across, obtuse or rounded, reddish brown; scales ovate, about 1.5 mm. long, obtuse, hyaline, somewhat cymbiform; achenes obovate, whitish, lustrous, 0.6 mm. long, obtusely 3-angled, with transversely oblong reticula­tions; stamens 1 or 2, the anthers 0.5 mm. long.  July-Oct. Common in wet places along rivers or in paddy fields.

Hon­shu, Shikoku, Kyushu. Pantropic.