SENSITIVITY IN PLANTS AND ANIMALS 65 



such sense organs absent as a rule from plants ? We 



say " as a rule," for the sense of touch is, at least in 



some plants, fairly well developed, but we have no 



evidence of the possession by plants of any of the 



other special 



sense organs 



(though attempts 



have been made 



to show that 



some plants at 



least do possess 



sense organs of 



a kind). Let us 



try and obtain 



an answer to this 



question. 



Self - preserva- 

 tion is obviously 

 of paramount 

 importance to 

 every living or- 

 ganism. It must 

 obtain food ; it 

 must avoid in- 

 jury ; it must 

 acquire the re- 

 quisite supplies 

 of heat, air, 

 moisture, and so 

 on, to enable it 



to live healthily ; these are the primary necessities 

 of its existence. 



The capacity for responding rapidly to contact Sense 

 with extraneous bodies is developed in the animal, " 

 in the first instance for the recognition of injurious 



FIG. 25. Cobseci 



