140 THE METHOD OF DARWIN, 



fertilization, he set himself the task of inter- 

 preting the complex arrangement of parts in 

 orchidaceous flowers in relation to the visiting 

 insects in accordance with that proposition. 



One of the most interesting and successful 

 applications of this principle is the following. 

 He has described various excrescences, warts, 

 ribs, ridges, etc. on the labellum, or large odd 

 petal of different orchids, the flowers of which 

 do not secrete nectar. He was haunted by 

 the question of the meaning of these absurdly 

 insignificant and irregular things, their rela- 

 tion to the other parts and to the visiting in- 

 sects. He said, " From the position relatively 

 to the viscid disk [by means of which the pol- 

 len is removed by visiting insects] which these 

 excrescences occupy, and from the absence of 

 any free nectar, it formerly seemed to me higlrly 

 probable that they afforded food, and thus 

 attracted either Hymenoptera or flower-feeding 

 Coleoptera. . . . Nevertheless it was a bold 

 speculation that insects were attracted to the 

 flowers of various orchids in order to gnaw the 

 excrescences or other parts of the labella; and 

 few things have given me more satisfaction 

 than the full confirmation of this view by Dr. 

 Cruger, who has repeatedly witnessed in the 

 West Indies humble-bees of the genus Euglossa 



