Petioles 5-30 cm, lfls emergent, short-stalked or virtually sessile, entire or wavy-margined, elliptic ovate to elliptic-obovate, 3-6 cm at anthesis, larger later; infl crowded at anthesis; pedicels 5-20 mm, sometimes 2 from one axil; cor whitish, usually purple-tinged, the tube ca twice as long as the 3-5 mm cal, the lobes lance-ovate, 5-7 mm; fr thick-walled, 6-9 mm; 2n=54, 108. In quiet shallow cold water; circumboreal, s. to N.J., Va., O., Ind., Mo., and Calif. May, June.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.