Japan Flora: Soft greenish herb 30-60 cm. high; stems usually erect, shorter than the leaves; leaves sometimes floating, the aerial ones compressed, 5-12 mm. wide, slightly keeled beneath; spikes 10-20 cm. long, simple, with leafy bracts much longer than the spike; pistillate heads approxi­mate, the lower ones often on short supra-axillary peduncles; staminate heads 1 or 2, adjacent to the pistillate, inconspicuous; fruit numerous, on pedicels about 1.5 mm. long, narrowly ob­long-fusiform, about 4 mm. long, 1.5 mm. wide, scarcely angled; style inclusive of sdgma about 1.5 nun. long. July-Aug.  Shallow ponds and lake margins. 

Hokkaido, Honshu (mountains of centr. distr. northw.). Eurasia and nw. America.

var. angustifolium Graebn. Plant much long. Shallow ponds in high mountains; Honshu (centr. distr. northw.)  Eurasia.