LUTHER BURBANK 



So in the case of the tiny snow-bunting and of 

 pelicans and herons, the white color of the plum- 

 age is seen to be advantageous to its wearer and 

 hence is easily explained according to the prin- 

 ciple of natural selection. The same is true of the 

 white plumage assumed by those species of grouse 

 and ptarmigan that winter in Arctic or sub-arctic 

 regions; and contrariwise, the pigmented coats of 

 the vast majority of the birds and animals of 

 temperate zones are accounted for on the same 

 principle. 



But just why the fruits of plants should almost 

 universally be pigmented seems at first not 

 quite so clear. It is ordinarily supposed to be 

 advantageous for a plant to have its fruit made 

 visible to the birds and animals, that the aid of 

 these creatures may be gained in disseminating 

 the seed. And it must be obvious that a 

 white blackberry would be as conspicuous in the 

 woodlands where this vine grows as are the jet 

 black berries of the ordinary type. 



Why, then, you ask, has not natural selection 

 developed a race of white blackberries? 



I am not sure that any one can give an 

 adequate answer. Perhaps it is desirable to have 

 the seeds of a plant protected from the rays of 

 the sun, particularly from those ultra-violet rays 

 which are known to have great power in producing 



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