17 



15a. Flowers 6 10 mm. wide, with a spur about the same length 



(14 dm. high, summer) (Rein Orchis) 35. 

 15b. Flowers 5 mm. wide or less; spur none (1 2 dm. high; summer) 



(Adder's Mouth) 16. 



16a. Pedicels less than 5 mm. long; lip broadest below the 



middle Adder's Mouth, Microstylis monophyllos. 



16b. Pedicels more than 5 mm. long; lip broadest near the 



apex Adder's Mouth, Microstylis unifolia. 



17a. Flowers spicate; lip distinctly 3-lobed (1 2 dm. high; early 



summer) 24. 

 17b. Flowers -solitary or two 18. 



18a. Leaf on the stem, lanceolate to ovate 34a. 

 18b. Leaf basal, round-ovate (2 dm. high or less; early sum- 

 mer) Calypso, Calypso bulbosa. 



19a. Leaves opposite and sessile near the middle of the stem (1 3 



dm. high; flowers in summer) (Tway-blade) 20. 

 19b. Leaves basal 21. 



20a. Lip deeply 2-cleft (flowers purplish) 



Tway-blade, Listera cordata. 



20b. Lip wedge-shape, with 2 round shallow lobes (flowers green- 

 ish-yellow) Tway-blade, Listera couyallarioides. 



21a. Lip an inflated sac about 4 cm. long 29d. 

 21b. Lip not sac-like 22. 



22a. Flower with a spur 1550 mm. long 23. 

 22b. Flower not spurred (1 2, dm. high; early summer) (Tway- 

 blade) 25. 



23a. Flowers purple or magenta, or with white markings 24. 

 23b. Flowers greenish, yellowish, or white (1 4 dm. high; summer) 

 (Rein Orchis) 36. 



24a. Leaf 1 (1 2 dm. high; early summer) 



Round-leaved Orchis, Orchis rotmidifolia. 

 24b. Leaves 2 (20 cm. high; late spring) 



Showy Orchis? Orchis spectabilis. 



25a. Lip about 10 mm. long, purple Tway-blade, Liparis liliifolia. 

 25b. Lip about 5 mm. long, yellowish-green 



Tway-blade, Liparis loeselii. 

 26a. Perianth 8 10 mm. long; lip with elongated point 



Rattlesnake Plantain, Epipactis decipiens. 

 26b. Perianth 4 6 mm. long; lip sack-like 27. 



27a. Raceme loosely flowered, one-sided 



Rattlesnake Plantain, Epipactis repens yar. ophioides. 



27b. Raceme closely flowered, not one-sided 



Rattlesnake Plantain 9 Epipactis pubescens. 



28a. Lip conspicuously sack-like, inflated (late spring and early 



summer) (Lady's Slipper) 29. 

 28b. Lip not sack-like nor inflated 32. 



x 



