INSECTS AND FLOWERS 243 



the circumstances that surround it." Moreover, the chief 

 factors which have influenced the evolution of highly 

 specialised flowers are not " natural " in the strict sense of 

 the term. For just as mankind, by a system of artificial 

 selection, or " breeding," has established races of domestic 

 animals in accordance with his needs or fancies, so insects 

 have left their mark upon the flowers. In a word, 

 natural selection has been superseded in large measure 

 by the intrusions of the insect ; and while we may admire 

 the elaborate mechanisms whereby the increase of the 

 plants is maintained in face of incalculable odds, we can 

 hardly extol them as the best conceivable. Indeed, such 

 flowers as orchids must probably be regarded as the out- 

 come of profitless variations controlled by the circum- 

 stances of the hour — in other words, by the visitations of 

 insects. The insects have gained much in nectar, but 

 the fruitfulness of the plants has steadily declined. It is 

 interesting to notice that a few flowers seem to be escaping 

 from this downhill progress. Our English bee-orchis 

 (Ophrys apifcra), though obviously designed to attract 

 insects, is seldom or never visited. This lack of attention 

 would involve other orchids in sterility. But in the bee- 

 orchis the anther cells open soon after the flower is fully 

 expanded, allowing the pollinia to fall out, the viscid 

 discs still remaining in the rostellum. In this position 

 the slightest movement of the flower — such as might be 

 caused, for example, by a breath of air — sets the elastic 

 caudicles vibrating, and the pollinia almost immediately 

 strike the stigma. In this way self-pollination is effected. 

 Thus, while many orchids that depend solely upon the 

 visits of insects remain barren, the bee-orchis apparently 

 produces as many seed-capsules as flowers. 



