Cypripedium

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  C. acaule

  1a. Plants with 2 basal leaves, the stem scapose; labellum with a cleft along its entire length on the adaxial (i.e., upper) surface
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  1b. Plants with 2–9 leaves alternately arranged on the stem; labellum with a round opening near the base on the adaxial surface
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    C. arietinum

    2a. Labellum 1–1.6 (–2.5) cm long, strongly red-veined, prolonged downward near the apex into a conical pouch; all 3 sepals distinct
  • See list of 2 species in 2b
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    2b. Labellum 1.5–5.4 cm long, neither red-veined nor prolonged downward to form a protruding sac; lateral sepals connate, thereby forming a single blade positioned beneath the labellum
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      C. reginae

      3a. Labellum white (rarely pink) and streaked with pink or purple; lateral petals white, not twisted, rounded to narrow-obtuse at apex; lateral sepals entirely connate
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      C. parviflorum

      3b. Labellum yellow, usually with purple veins; lateral petals spotted, streaked, or entirely suffused with red-purple or red-brown, rarely unmarked and then ± yellow-green, twisted, acute to acuminate at apex; lateral sepals connate except at tip, 
forming a bilobed apex

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 Show photos of:   Each photo represents one species in this genus.