Japan Flora: culms 30-50 cm. long, nearly smooth; leaf-blades 1.5-2.5 mm. wide; spikes 3-5 sometimes 2, somewhat approximate or rather loose, gynecandrous, globose, the terminal with a slightly longer staminate portion than in those of the lateral; perigynia nearly twice as long as the scales, 4-5 mm. long, strongly spreading to somewhat deflexed, lanceolate-ovate, strongly convex on back, faintly nerved, gradually long-beaked, minutely bifid at tip, prominently thickened at the spongy base; achenes tighdy inclosed; stigmas  2. May-July. Wet places; Hokkaido, Honshu, Kyushu. s. Kuriles. 

var. monticola Ohwi Culms 10-30 cm. long; spikes slightly smaller; perigynia 3.5-4 cm. long, broadly ovate-lanceolate, with a slightly longer beak.  Wet places usually in mountains; Hokkaido, Honshu (centr. distr. and northw.)

var. yakushimana Ohwi. Culins short, to 10 cm. long, leaf-blades somewhat involute, narrow; perigynia 4 mm- long, nearly smooth, short-beaked. Wet places in high mountains; Kyu­shu (Yakushima)