168 LIVING PLANTS 



among the higher insects, and that the form 

 and odor of the flower are the features most 

 effective in securing the attention of pollen- 

 carrying animals. 



It is of course undeniably proven that some 

 colors do attract insects to flowers, and that 

 pollination is accomplished as a result of the 

 visit. If, however, the color is supposed to be 

 developed as an adaptation, guided by the 

 selective agency of the animal, some difliculties 

 arise. In the first place, it is to be said that 

 the selective power of the insect has been ex- 

 ercised only in comparatively recent times — 

 since it developed the sense of color. Secondly 

 the red, yellow, and white floral markings 

 of leaves and flowers, as well as of other mem- 

 bers, are due to katabolic or breaking down 

 processes, and originate as well in injured or 

 deteriorated organs in which the food-forming 

 capacity has suffered diminution. In some 

 instances, as in the screen of colored leaves, 

 the formation of the pigments is due to the 

 regulatory action of the plant, and serves the 

 purpose of checking the diminution of the 

 food-forming power, and hinders the disin- 

 tegration of plastic substances, to which it 

 owes its origin. 



With all of the probabilities taken into ac- 

 count it can only be said that the selective 

 power of animals toward plant colors may 



