Chap. VIII. OYPEIPEDIUM. 229 



in all other Orchids except Vanilla belongs exclusively 

 to the rostellum and the two confluent stigmas. These 

 latter organs, on the other hand, in Cypripedium en- 

 tirely lose their viscidity, and at the same time become 

 slightly convex, so as more effectually to rub off the 

 glutinous pollen adhering to the body of an insect. 

 Moreover in several of the North American species, 

 as in G. acaule and pvheseens, the surface of the stigma 

 is beset, as Professor Asa Gray remarks, * " with 

 minute, rigid, sharp-pointed papillae, all directed for- 

 wards, which are excellently adapted to brush off the 

 pollen from an insect's head or back." There is one 

 partial exception to the above rule of the pollen of 

 Cypripedium being viscid while the stigma, is not 

 viscid and is not convex ; for in C acaule the pollen 

 is more granular and less viscid, according to Asa 

 Gray, than in the other American species, and in 

 0: acaule alone the stigma is slightly concave and 

 viscid. So that here the exception almost proves the 

 truth of the general rule. 



I have never been able to detect nectar within the 

 labellum, and Kurrt makes the same remark with 

 respect to C. calceolus. The inner surface of the la- 

 bellum, howeyer, in those species which I examined, 

 is clothed with hairs, the tips of which secrete little 

 drops of slightly viscid fluid. And these if sweet or 

 nutritious. would suffice to attract insects. The fluid 

 when dried forms a brittle crust on the summits of the 

 hairs. Whatever the attraction may be, it is certain 

 that small bees frequently enter the labellum. 



Formerly I supposed that insects alighted on the 

 labellum and inserted their proboscides through either 



* 'American Journal of Science,' t 'Bedeutung der Nettarien, 



vol. xxxiv, 1862, p. 428. 1833, p. 29. 



