230 CYPRIPEDE^. Chap. VIII. 



of the orifices close to the anthers ; for I found that 

 when a bristle was thus inserted the glutinous pollen 

 adhered to it, and could afterwards be left on the 

 stigma ; but this latter part of the operation was not 

 ^^■ell effected. After the publication of my book 

 Professor Asa Gray wrote to me * that he was convinced 

 from an examination of several American species that 

 the flowers were fertilised by small insects entering the 

 labellum through the large opening on the upper sur- 

 face, and crawling out by one of the two small orifices 

 close to the anthers and stigma. Accordingly I first 

 introduced some flies into the labellum of C. puhescens, 

 through the large upper opening, but they were either 

 too large or too stupid, and did not crawl out properly. 

 I then caught and placed within the labellum a very 

 small bee which seemed of about the right size, namely, 

 Andrena parvula, and this by a strange chance proved, 

 as we shall presently see, to belong to the genus on 

 which in a state of nature the fertilisation of G. calceo- 

 lus depends. The bee vainly endeavoured to crawl out 

 again the same way by which it had entered, but always 

 fell backwards, owing to the margins being inflected. 

 The labellimi thus acts like one of those conical traps 

 with the ed-ges turned inwards, which are sold to catch 

 beetles and cockroaches in the London kitchens. It 

 could not creep out through the slit between the folded 

 edges of the basal part of the labellum, as the elongated, 

 triano-ular, rudimentary stamen here closes the passao-e. 

 Ultimately it forced its way out through one of the 

 small orifices close to one of the anthers, and was 

 found when caught to be smeared with the glutinous 

 pollen. I then put the same bee back into the label- 

 lum ; and again it crawled out through one of the small 



• Sec also ' American Journal of Science," vol. xxxiv. 1862, p. 427. 



