LIVING PLANTS 



more important particular, does the animal 

 with its power of locomotion show the need 

 of a different set of senses from those of the 

 plant. The ingestion of a large amount of 

 solid food requires the animal to search for a 

 suitable supply ; while the plant, partaking 

 only of food in solution and in comparatively 

 small quantities, is enabled to secure it by 

 slender feeders extending into the surround- 

 ing medium. In securing food and protecting 

 itself from injury the animal makes use of 

 three important senses: smell, hearing and 

 sight. The plant with its fixed position and 

 simpler requirements does not need these 

 senses ; they would be useless to it, and have 

 not been developed. 



We may safely conclude that in so far as 

 animals and plants respond in a marked 

 F df d n^anner to stimulation, it is along two dis- 

 tinct lines, to correspond with the necessities 

 of free organisms on the one hand, and of 

 fixed organisms on the other. 



For a fixed organism orientation is of prime 

 necessity. The roots of a plant must pene- 

 trate the soil and its foliage be spread to the 

 air. 



Yet the root or shoot has no power to de- 

 viate from extension in a straight line unless 

 it is acted on by some external force, no more 

 than a cannon ball or other moving body has 



organisms 



