Japan Flora: Rhi­zomes thickened, creeping; culms 60-100 cm. long, stout, spongy-thickened at base, nearly glabrous; leaf-blades flat, rather thick, 8-15 mm. wide, the basal sheaths pale, sometimes partially sanguineous; upper 3-7 spikes staminate, linear, 3-6 cm. long, contiguous, the lower 2-5 pistillate, distant, long- cylindric, 5-10 cm. long, about 1 cm. across, densely many­flowered, nearly sessile except the lowest one usually long- peduncled and sometimes nodding, the bracts leaflike; pistillate scales oblong-lanceolate, castaneous or ferrugineous, some­times pale, scarious toward the margins especially broadly so above; perigynia longer than the scales, 5-6 mm. long, spread­ing, broadly ovoid, firmly membran이is, strongly inflated, stramineous-green, sometimes partially dark brownish, lus­trous, nerved, abruptly long-beaked, bifurcate at tip; stigmas 3. June-Aug. Swamps and shallow water around ponds. 

Hokkaido, Honshu (n. and centr. distr.). Korea, Ussuri, Sakhalin, Kuriles, Siberia, and N. America.