Japan Flora: Rhizomes long-creeping; culms 20-40 cm. long, acutely 3-angled, very scabrous above; leaf-blades flat, 2.5-3 mm. wide; inflorescence dense, 1.5-2 (-3) cm. long, ovoid to oblong-ovoid, ebracteate, the spikes 8 to 10, androgynous or unisexual, ovoid, 5-8 mm. long, red­dish brown; pistillate scales ovate, reddish brown; perigynia slightly shorter than the scales, oval, 4-5 mm. long, com­pressed, spongy, several-nerved on both sides, scabrous, winged on the margins, short-beaked; style bifid. May-June.

Hon­shu (Kanto and ne. Shinano); rather rare. Korea, Man­churia, and e. Siberia