Stems 15--40 cm ´ 1--2 mm. Leaves 0.9--1.8 cm; sheath 2.5--3.4 mm wide, apex rounded to truncate; blade 1.5--2 mm wide, teeth 20--40 per side, invisible to unaided eye, apex acute. Flowers 1 per axil. Staminate flowers 2.3--2.8 mm; anther 4-loculed. Pistillate flowers 2.7--3.1 mm. Seeds 2.3--2.5 ´ 0.6--0.8 mm; aeroleareoles of testa in 20--40 longitudinal rows. Chromosome number unknown not available. Flowering late summer. Lakes and rivers; 0--100 m; Man., Ont.; Que.; Ind., Iowa, Mass., Mass., Mich., Minn., N.Y., Wis.