i 3 o 



THE FACTORS 



[Part I 



between insular and continental conditions of life, and for paving the way 

 towards an explanation of the more complex relations that affect oceanic 

 islands. As on oceanic islands, so also on coast-islands, the relative number 

 of entomophilous species is smaller than on continents ; the mere separa- 

 tion of the coast-island from its adjacent mainland has consequently 

 caused the disappearance of a portion of these species. At the same 

 time, a reduced number of insects is also noticeable. Both phenomena 

 are to be attributed to the strong winds, which on the one hand lessen 



Fig. 66. Angraecum eburneum, Thouars, in its native habitat. Seychelles. To the right a 

 zingiberaceous plant. From a photograph by Brauer. 



the number of insects and the species of plants associated with them, 

 and on the other hand favour anemophilous flowers 1 . 



Up to the present time observations on the pollination of flowers, 

 with few exceptions, have been made only in temperate regions ; in the 

 tropics, only a few and generally fragmentary observations have been 

 recorded, although many tropical forms of flowers appear to be adapted 

 to quite definite pollinators. From this point of view it is only necessary 



1 See p. 79. 



