Stems 30--90 cm ´ 0.8--1 mm. Leaves 0.9--1.3 cm; sheath 1--1.5 mm wide, apex rounded; blade 0.5--1.6 mm wide, teeth 50--100 per side, invisible to unaided eye, apex acute. Flowers 1 per axil. Staminate flowers 2--3 mm; anther 1-loculed. Pistillate flowers 2.9--4 mm. Seeds 3.3--3.8 ´ 0.5--0.7 mm; aeroleareoles of testa in 50--60 longitudinal rows. Chromosome number unknown not available. Flowering late summer. Shallow water of rivers; of conservation concern; 0--100 m; N.Y.