264 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1920. 



Table 8. — Soil reactions of orchids. 



Name (Gray nomenclature). 



Num- 

 ber of 

 tests. 





Circumneutral. 



300+ 100 30+ 10 3+ 



3+ 10 



CYPRIPEDIUM GROUP. 



(Lady's slipper orchids.) 



Cypripedium candidum 



hirsutum 



pubescens 



parviflorum 



arietinum 



acaule 



HABENARIA GROUP. 



(Spurred orchids.) 



Habenariadilatata 



hyperborea 



media (var.) , 



obtusata 



Orchis spectabilis 



Habenariaftmbriata 



peramoena 



psycodes 



lacera 



bracteata 



hookeri 



orbiculata 



macrophylla 



nivea 



clavellata 



flava 



cillaris 



blephariglottis 



cristata 



Canbyi(X) 



bicolor (X) , 



Integra 



POGONIA GROUP. 



(Bearded orchids.) 



Pogoniatrianthophora 



verticillata 



Calopogon pulchellus 



Pogonia ophioglossoides 



di varicata 



Arethusa bulbosa 



SERAPIAS GROUP. 



(Hellebore orchids.) 

 Serapias Helleborine 



EPIPACTIS GROUP. 



(Rattlesnake orchids.) 



Epipactis pubescens 



ophioides (var.) 



tesselata 



SPDRANTHES GROUP. 



(Twisted-spike orchids.) 



Spiranthes Romanzoffiana 



lucida 



odorata 



cernua 



praecox 



vernalis 



gracilis 



beckli 



X 



X 







c 

 I 



I 



A 



AA 



C 



C 



C 



A 



I 



A 



A 



A 



A 



A 



A 



A 



A 



A 



AA 

 AA 

 AA 

 AA 

 AA 

 AA 

 AA 

 AA 



C 

 A 



AA 

 AA 



AA 

 AA 



C 

 I 

 A 

 I 

 A 

 A 

 A 

 AA 



