Heteranthera limosa (Sw.) Willd.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
Species Description - Aerial lvs emersed, the blade 1–5 cm long and about half as wide, oblong to ovate, acutish, with cuneate to truncate base; petioles to 1.5 dm; spathe folded, abruptly caudate-acuminate, 1–4.5 cm, enclosing 1 fl; fls purple to white, the perianth-tube 1.5–4.5 cm, the lobes 5–15 mm, about equally spreading, the 3 upper ones basally yellow; stamens subequal, with straight filaments, the lateral ones yellow, the central one purple or white; style glabrous; 2n=14. In shallow water at the edges of ponds and ditches, or wholly emersed on mud; Mississippi R. drainage from Ky. to Io. and S.D., s. to S. Amer.; also Calif. to Ariz. and w. Mex.