GENERAL BIOLOGY 



entiations which we find are nearly all in the line of 

 structures for elaborating, taking up, and storing 

 foods, and of supporting the plant-body (omitting, 

 of course, all consideration of the reproductive 

 function, which will be discussed in a later chap- 

 ter). 



Accordingly, we find little trace of nervous system 

 or muscular system. Yet some plants, like the 

 Mimosa or sensitive plant, react to stimuli with a 

 definiteness that is comparable to a nervous reflex 

 in animals. The leaf of the " Venus' flytrap," 

 when an unwary insect touches it, springs shut with 

 such suddenness and vigor as to catch the prey and 

 hold it fast. This action is brought about by three 

 sensitive spines which may therefore be held to be 

 analogous to animal sense-organs. A number of 

 plants have the habit of folding their leaves at night, 

 in " sleep," the stimulation being the change from 

 daylight to darkness. Moreover stimuli are trans- 

 mitted (usually slowly, to be sure) from one por- 

 tion of the plant to another. Plant tissues may be 

 anesthetized, and when stimulated, they show 

 " fatigue." We may conclude, therefore, that al- 

 though the basis of the mechanism may be entirely 

 different from that of animals, yet, in so far as the 

 plant tissue is differentiated sufficiently to receive 

 stimuli from without and transmit them to other 

 parts of the plant-body, there to bring about an 

 appropriate response, it may be asserted that plants 

 possess a rudimentary nervous system. They differ 

 from most animals in lacking any sort of a coordi.nat- 



