Glabrous aquatic perennial to 1 m, the hollow upright stem usually partly submersed; lvs in a basal rosette, linear, fleshy, hollow, 2-9 cm, outcurved near the tip; cauline lvs minute, filiform; raceme emersed, few-fld; bracts ovate, 2-3 mm; bracteoles none; sep 2 mm; cor pale blue or white, 1-2 cm, the lower lip bearded at base within; 2n=14. Borders of ponds, usually in sand; Nf. to N.J., w. to Minn.; also on the Pacific coast and in Europe. July-Sept.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.