Stems elongate, submersed; lower lvs alternate, 3 cm, repeatedly dichotomous into filiform segments, each bearing bladders; uppermost lvs subtending the peduncle in whorls of 4-7, the rachis of each 1-4 cm, inflated, usually thickest at or below the middle, bearing at the tip a series of finely dissected branches; peduncles 3-5 cm; bracts 2-3 mm, at least as wide as long, sometimes lobed; lower pedicels 1-2 cm; fls (1-)3-5(-7), yellow; sep 3-4 mm; upper cor-lip subrotund; lower lip subrotund, 8-10 mm, shallowly 3-lobed, with a prominent small palate; spur shorter than and appressed to the lower lip; 2n=28. Ponds along or near the coastal plain; Me. to Fla. and Tex.; nw. Ind. May-Aug. (U. inflata var. minor)
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.