Japan Flora: Rhizomes elon­gate; culms soft, terete, 30-70 cm. long, 1,5-5 mm. thick, strongly compressed when dried, the sheaths hyaline, truncate at apex, sometimes addish at base; spikelets lanceolate to ovoid, 1-3 cm. long, 3-6 mm. thick, rather obtuse at apex, ferrugineous, densely many-flowered; scales broadly lanceolate to narrowly ovate, mm. long, slightly obtuse to acute; achenes yellow to tawny, turgid-biconvex, slighdy lustrous, obovate-orbicular, 1.5-2 mm. long, nearly smooth, the style base depressed-deltoid, spongy, half as wide as the achene, the bristles 5-6, twice as long as the achene, retrorsely scabrous. July-Oct. Shallow ponds and wet places.

Hokkaido, Honshu, Kyushu; rather common. Korea, Manchuria, and Ussuri. The typical phase is widely distributed in the north­ern part of the N. Hemisphere.