Stems 7--51 cm ´ 0.1--1.7 mm. Leaves 0.9--3.3 cm; sheath 1.2--2.5 mm wide, apex rounded; blade 0.5--2.1 mm wide, teeth 18--42 per side, visible to unaided eye, apex round obtuse to acuminate. Flowers 1 per axil. Staminate flowers 1.5--2.4 mm ; anthers 1-loculed. Pistillate flowers 1--3.4 mm. Seeds 1.6--2.2 ´ 0.3--0.8 mm; aeroleareoles of testa in 20 longitudinal rows. 2n = 48. Flowering spring--fall. Lakes, streams, and canals; 0--100 m; Ala., Fla., Ga.