Underground parts very delicate, rarely collected, with bladders 0.5 mm; aerial lvs, if present, linear, to 1 cm; flowering branches very slender, erect, 3-20 cm, 1-10-fld; bracts ovate or elliptic, 1-2 mm, peltate, attached at or below their middle; pedicels 4-15 mm; cor commonly yellow, the lower lip usually 4-7 mm, with prominent palate and widely spreading limb; spur about equaling the lip and appressed to its lower surface. Wet soil and very shallow water, often among mosses; N.S. to Fla. along the coastal plain, thence w. to Ark. and Tex. May-Sept. (Setiscapella s.) A depauperate form 2-5 cm with 1-3 whitish fls 1-2 mm sometimes occurs with the normal form. (U. cleistogama; Setiscapella c.)
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.