DEVELOPMENT OF MODERN COMPARATIVE PSYCHOLOGY 



495 



the level of the brute, ' ' the practical conse- 

 quences being "the demoralisation and 

 brutalisation of man." 



Important developments took place 

 during this period in the field of plant 

 behavior (47, 53). The term tropism 

 had been introduced by the botanist 

 DeCondolle as early as 1835 and long 

 before this Knight (1805) had shown the 

 effect of gravitation on the direction of 

 growth in seedlings. Aside from the 

 work of Darwin and F. Darwin, which 

 will be discussed at some length below, 

 valuable contributions to the behavior 

 aspect of plant life were made by Sachs , 

 Pfeffer, Strasburger, Weisner, Stahl and 

 many other botanists of the period. 

 Plant behavior was usually thought of as 

 being purely physiological and as lying 

 entirely outside the pale of psychology 

 and hence it escaped for the most part the 

 evil influence of anecdote and anthropo- 

 morphism. 



Darwin himself gave no little time to 

 the experimental investigation of various 

 phases of plant life. His earlier interest 

 was largely confined to morphological 

 variation under domestication as an in- 

 stance of the evolutionary principle, and to 

 such related topics as fertilization and 

 sexual dimorphism. However, he later 

 -took up the problem of plant behavior, 

 and in 1875 published a volume on climb- 

 ing plants and one on insectivorous plants, 

 the latter attracting wide attention be- 

 cause of the novelty of the material. 



Darwin's most notable contribution to 

 the study of plant behavior was The Power 

 of Movement in Plants, written in collabora- 

 tion with his son, Francis, and published 

 two years before his death. The book is 

 replete with simple but ingenious experi- 

 mental methods, some of which have 

 become classic, and with results inter- 

 preted more often than not with rare 

 insight. Darwin found that practically 



all parts of the plant — stems, leaves, roots, 

 flowers, etc. — normally perform circum- 

 nutation movements even when shielded 

 from external stimulation. From this 

 general fact he was led to believe that 

 all tropistic responses of plants were 

 merely variations of this inner power of 

 movement directed in part by such external 

 energies as gravity, light, pressure, etc. 

 He was among the first to recognize 

 special sensitive zones such as tip of root 

 and shoot, transmission of excitation 

 through the tissues to point of curvature, 

 and the general similarity of plant and 

 animal behavior in its more fundamental 

 aspects. The tip of the radicle, which 

 exhibits a multiform sensitivity in pene- 

 trating the ground, seemed to him to act 

 "like the brain of one of the lower 

 animals" in directing the general move- 

 ment of the root. 



The contribution of the anecdotalists 

 was relatively insignificant in comparison 

 with that of- these various groups of 

 workers who, in one manner or another, 

 were making direct observations of plant 

 and animal behavior. At best the anec- 

 dotal material served only a temporary 

 purpose in connection with the contro- 

 versy over the mental evolution of man. 

 Furthermore, the anecdotalist movement 

 was a positive evil insofar as its influence 

 tended to retard scientific investigation of 

 the behavior of the higher animals. The 

 observation of the naturalist and the more 

 careful studies of anatomist and physiol- 

 ogist, insofar as their findings were 

 relevant, represent the more permanent 

 contribution of the period to comparative 

 psychology. 



THE EXPERIMENTAL PERIOD 



Beginnings of the movement 



Although Darwin stands apart as the 

 great pioneer spirit in the rise of modern 



