SPECIAL SENSES 



The passing of the present century has seen 

 an increasing tendency toward the serious 

 use of terms for plant activity borrowed from 

 the YoHtional and neural manifestations of 

 animals. These, in part, are suggested by 

 purely superficial analogy, and intended sole- 

 ly to lend greater attractiveness to the narra- 

 tive, as in Charles Darwin's description of a 

 twining plant, whose horizontal extremity 

 repeatedly slid past the support which tem- 

 porarily arrested its progress as it swung 

 slowly around in a circle. ''This movement 

 of the shoot had a very odd appearance," he 

 says, "as if it were disgusted with its failure, 

 but was resolved to try again." Yet in part 

 there is implied an obscure but real analogy, 

 as when the same author in another work 

 sums up his studies of the root tip with the 

 assertion that in its power to direct move- 

 ment in the adjoining parts it ''acts like the 

 brain of one of the lower animals." 



So long as the comparison of animal and 

 vegetable activities rested largely upon exter- 

 nal appearances, with verj- limited under- 

 standing of the changes within the organism 

 by which they are brought about, no consid- 

 erable advance was possible. At first the in- 

 terpretation was necessarily based upon 

 human and animal analogies. As JuHus Sachs 

 has admirably said in his "History of 



Application 

 of terms 



Knowledge 

 of mechantsm 



