Thallus broadly oval to obovate, anthocyanic beneath, (3-)5-8(-10) mm, ±evidently 5-15-nerved, forming turions especially in the fall; roots mostly 5-12; spathe open only at the top; seeds 1 or 2, smooth or minutely reticulate; 2n=30, 40, 50. Quiet water; nearly cosmopolitan, and throughout our range.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.