CHAPTER XII 



VARIOUS MOVEMENTS IN PLANTS 



As a teacher of botany for nearly forty spring and summer 

 seasons, and from the first interested in certain plant- 

 movements, and also in trying to teach the elements of 

 vegetable physiology in practical classes, the writer has 

 had some experience of the intricacies and obscurities of 

 the subject. From Sachs, the great teacher of vegetable 

 physiology in our young days, he received inadequate light ; 

 and though Darwin's ' Movements of Plants ' (1889) 

 seemed helpful, and his discovery of ' circumnutation ' 

 for him a common property of shoots and leaves, and 

 even of roots, from which more specific movements might 

 be viewed as evolutionary specialisations under definite in- 

 fluences was highly attractive, yet this theory did not fully 

 carry conviction. For such records of circumnutation might 

 be but complex resultants of the plant's responses to many 

 changing conditions. But how to analyse these ? Experi- 

 ments and observations have of course increased, and 

 also attempts to co-ordinate and interpret them ; witness 

 the portly third volume of Pfeffer's great ' Vegetable 

 Physiology,' which is very largely thus occupied, but still 

 without bringing to the subject the needful simplicity 

 and generalisation. We now see a twofold reason for this 

 failure of vegetable physiology hitherto. First because the 

 vegetable physiologists, despite many and praiseworthy 

 endeavours, but with their imperfect instrumentation 

 and correspondingly slow and little magnified records, could 



