5. Cypripedium L. (lady’s slipper)
Plants
with rhizomes. Flowering stems 1‑several, hairy, with 1–3 terminal
flowers, each subtended by a leaflike bract. Leaves 3–10 (2 elsewhere), green,
with both basal and alternate positions along the flowering stems, sessile,
lanceolate to ovate or elliptic, usually somewhat corrugated or ribbed, hairy.
Lateral 2 sepals usually united to the tip, similar in size and shape and
opposite the upper sepal, positioned behind the lip. Lateral petals spreading,
in some species somewhat downward arching or drooping. Lip enlarged to form a
slipperlike pouch. Column with 2 stamens on either side near the tip, the tip
with a large, ovate to triangular staminode. Capsules erect or nearly so, 20–30
mm long, elliptic in outline, strongly ribbed. Forty species, North America,
Europe, Asia.
The
hairs present on foliage of Cypripedium species cause dermatitis in some
people. These beautiful orchids have suffered more than most species in Missouri from overcollecting (see below).
Cypripedium is unique among Missouri orchids in having 2
stamens, rather than 1, with a staminode also produced, and in having granular
pollen. The species are mostly pollinated by various smaller bees (less
commonly by beetles and flies), which are deceived into visiting the flowers by
color and fragrance (the flowers offer no rewards to insects). The insects
enter the pouchlike lip and can only exit through smaller openings on either
side of the column toward the rear of the lip, which involves rubbing against
the stamens and stigma. Occasionally, larger insects, such as bumblebees and
moths, will enter the lip but are too large to pass through the exit holes and
sometimes become trapped and die.