Stems free-floating or creeping on the soil under shallow water; lvs numerous, mostly 0.5-2 cm, commonly 3-parted at base and then 1-3 times dichotomous, the segments slender, flat, not much narrower in successive dichotomies, the ultimate ones rather blunt; bladders on specialized branches distinct from the lvs; fls mostly 2-4 in a lax raceme on an emergent peduncle 6-20 cm; pedicels to 15 mm, remaining erect; cor yellow, the lower lip 8-12 mm, with well developed palate, nearly twice as long as the upper lip; spur nearly as long as the lower lip; 2n=44. Shallow water; circumboreal, s. to Del., Ind., and Calif. Summer.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.