i8 - 



29a. Lip white (13 dm. high) 



White Lady's Slipper, Cypripedium candidum. 

 29b. Lip yellow (27 dm. high) 30. 

 29c. Lip white, with crimson or purple markings 31. 

 29d. Lip pink (1 4 dm. high, late spring) 



Stemless Lady's Slipper, Cypripedinm acaule. 

 30a. Lip 23 cm. long. 



Small Yellow Lady's Slipper, Cypripedinm parviflorum. 

 30b. Lip 3.5 5 cm. long 



Large Yellow Lady's Slipper, Cypripedium parviflorum var. pubescens. 



31a. Lip 2 cm. long or less; sepals separate (1,5 3 dm. high) 



Ram's Head Lady's Slipper, Cypripedium arietinum. 

 31b. Lip 3 cm. long or more; the 2 lower sepals united 



Showy Lady's Slipper, Cypripedium hirsutum. 



32a. Flowers solitary in the axils, or solitary and terminal; not 



spurred 33. 



32b. Flowers in terminal racemes, spurred 38. 



33a. Leaves a whorl of 5 (2 3 dm. high; petals greenish; late sum- 

 mer) Whorled Pogonia, Pogonia yerticillata. 

 33b. Leaves alternate 34. 



34a. Leaves lanceolate or narrowly ovate, 2 8 cm. long, nar- 

 rowed at base; flower terminal (1 4 dm. high; flowers pink 

 purple, early summer) Snake Mouth, Pogoiiia ophioglossoides. 

 34b. Leaves ovate, 12 cm. long, clasping; flowers axillary 

 (5 20 cm. high; flowers purple, summer) 



Nodding Pogonia, Pogonia trianthophora. 

 35a. Leaf basal; spur nearly straight 



Rein Orchis, Habenaria obtusata. 

 35b. Leaf on the stem; spur strongly curved 



Rein Orchis, Habenaria clavellata. 



36a. Flower-stalk without bracts below the raceme; flowers yel- 

 lowish-green Rein Orchis, Habenaria hookeri. 

 36b. Flower-stalk bearing bracts below the raceme; flowers 



greenish-white 37. 



37a. Spur 15 25 mm. long Rein Orchis, Habenaria orbicnlata. 

 37b. Spur 3050 mm. long Rein Orchis, Habenaria macrophylla. 



38a. Lip fringed (Fringed Orchis) 43. 

 38b. Lip not fringed (Rein Orchis) 39. 

 39a. Lip with 2 3 evident teeth at apex 40. 

 39b. Lip without apical teeth 41. 



40a. Stem-leaves 3 or more Rein Orchis, Habenaria bracteata. 

 40b. Stem-leaves 2 35b. 



41a. Flowers white Rein Orchis, Habenaria dilatata. 



41b. Flowers greenish-yellow 42. 



42a. Lip lanceolate, tapering toward the apex 



Rein Orchis, Habenaria hyperborea, 

 42b. Lip oblong, truncate at the apex 



Rein Orchis, Habenaria flava. 



