1a. var. parviflorum (Salisb.) Fernald (small yellow lady’s slipper)

C. parviflorum Salisb.

Leaves (3–)4–6 per flowering stem. Sepals and lateral petals reddish purple to brown, greenish yellow in a rare, albino form. Lateral petals 3.5–5(–8) cm long. Lip 2–3 cm long.

Scattered nearly throughout Missouri, but somewhat more common in the western half of the state (U.S., Canada). North‑ and east‑facing slopes of ravines and stream valleys in rich, mesic, upland forests, rarely on seepy ledges or in moist soil of shallow depressions at the edge of glades.

A rare albino form of this taxon has been recorded from Shannon and Crawford Counties. In these plants, the sepals and lateral petals are yellowish green and the lip is white, causing the flowers to resemble those of C. candidum. These unusual plants can generally be distinguished from the small white lady’s slipper by their longer stems, broader leaves, generally denser pubescence, and larger flowers.