Callitriche stagnalis Scop.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
Species Description - Fr suborbicular, 1.5–2 mm long and wide, the carpels distinctly wing-margined their whole length; 2n=10; otherwise much like no. 3 [Callitriche palustris L.]. In cold ponds and streams; native of Europe, intr. at scattered stations in our range and elsewhere in n. U.S. and s. Can.