Japan Flora: Rhizomes densely tufted, forming small clumps; culms 10-30 cm. long, slender, firm, glabrous; leaf­blades erect, stiff, yellowish green, 1.5-2.5 mm. wide, gradually acuminate, the basal sheaths stramineous; spikes 3 or 4, erect, closely contiguous, the lower ones sometimes distant and peduncled, the termind staminate, linear, 7-15 mm. long, light ferrugineous, the lateral pistillate, oblong-globose, 5-8 mm. long, densely flowered, subsessile, the lowest bract leaf­like, much longer than the inflorescence, short-sheathing; pistillate scales broadly ovate, rather acute, ferrugineous; perigynia longer than the scales, 2.5-3 mm. long, broadly obovoid, turgid, 3-angled, thick-membranous, glabrous, strongly several-nerved, yellowish green, abruptly short- beaked, the tip rigid, deeply 2-toothed; stigmas 3, short, slen­der.  June-July. Wet places in lowlands and highlands. 

Hokkaido, Honshu (Shinano to Hitachi Prov. and northw.); rather rare. Sakhalin, s. Kuriles, Kamchatka, and N. America. 

f. oederioides (Tatew. & Akiyama) T. Koyama. A much depauperate phase.  Hokkaido.