Herbs, perennial. Roots closely to widely spaced along rhizome, slender, fleshy; rhizomes short to elongate. Stems leafy or scapose. Leaves alternate, in single radical pair, or subopposite near midpoint of stem, ascending to spreading, plicate, bases sheathing stem. Inflorescences terminal, solitary; flowers solitary or 2-several in lax racemose spike; bracts large, foliaceous. Flowers resupinate, showy; sepals distinct or lateral sepals usually connate proximal to lip forming synsepal; petals entire; lip inflated, slipper- or sac-shaped, with adaxial orifice; pollinaria absent; loose granular pollen in 2 lateral anthers, dorsal anther a large subapical staminode; stigma free, 2-3-lobed. Fruits capsules, ellipsoid to oblong-ellipsoid.
Sep and lateral pet somewhat differentiated, widely spreading, the 2 lower sep usually connate; lip a large inflated pouch, its margins ±inrolled around the orifice; column declined over the orifice of the lip, bearing a fertile stamen (with granular, irregularly coherent pollen) on each side and dilated staminode above; perennial from fibrous roots, the erect stem bearing 2-several basal or cauline lvs and 1 or 2 large fls. 50, N. Temp.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.