Bacopa rotundifolia (Michx.) Wettst.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
Species Description - Stems typically submersed with the tips floating, less often emersed, 2–6 dm, the younger parts usually hairy but soon glabrate; lvs very thin, obovate to subrotund, 1–3.5 cm, entire, palmately 5–13-veined; fls usually 2–4 from the uppermost nodes, on pedicels (0.5)1–1.5 cm, without bractlets; sep 3–5 mm, obtuse, the upper one rotund-elliptic, obscurely to evidently reticulate-veiny; cor white with a yellow throat, narrowly campanulate, mostly 4–10 mm, its lobes equaling or a little shorter than the tube, the 2 upper united half-length; stigmas 2, distinct; 2n=36. Shallow water and wet soil; Ind. to Io., N.D., and Mont., s. to Miss. and Tex., and occasionally intr. elsewhere, as in tidal Va. and Md. June–Sept. (B. simulans; Bramia r.; Macuillamia r.)