Cypripedium calceolus L.

Abstract

A perennial herb with horizontal rhizome (diameter about 6mm) up to 10cm underground. Roots long and fleshy, diameter up to 2mm. Stem 20-60(70) cm, glandular-pubescent with brown basal sheaths; leaves 3-5, elliptical to ovate-oblong, acute to acuminate, sparsely pubescent (oval lanceolate, somewhat pleated, large), (7)11-17(22) cm long, (3)5.58(10) cm wide, veins obvious, bracts leaf-like, exceeding flowers; flowers 1-2(3) large; perianth segments purple-brown; dorsal outer tepal ('sepal') lanceolate, suberect, 3.5-6cm long and 1.5-2.5 cm wide; lateral 'sepals' joined, hanging below labellum 3.5-5.5 cm, free tips up to 5mm; inner tepals ('petals') 4-7 cm long and 0.5-1 cm wide, horizontal, twisted; labellum yellow, shoe-shaped (length 34cm, width 2-3 cm, depth 1.5-2 cm), reflexed, covered with viscous hairs inside, not spurred; staminode petaloid shield-shaped, white with red spots, 1-1.2 cm long, 0.7-0.9 cm wide; ovary elongate, somewhat curved, pubescent (glandular hairs), not twisted, pedicellate. Two fertile anthers, one on each side of style; stigma and staminode forming a flat appendage on the front of the column. Capsule up to 3 cm long and about 0.9 cm in diameter, containing 6000-17 000 seeds; seeds oblong about 1 mm long with a mass of a few micrograms (seed volume 0.02 mm3). From continental Europe, the all-yellow flowered var. fiavum Rion has been recorded (Davies et al. 1984). This exceedingly rare orchid was formerly more widespread in northern England in limestone woodland; it is more plentiful in wooded sites in northern Europe, but everywhere has suffered from collecting.