TREFACE ix 



SO various, are ultimately reducible to a fundamental unity 

 of reaction. 



This demonstration has been the object of the present 

 work, and not that treatment of known aspects of plant- 

 movements which is to be found detailed together with the 

 history of the subject, in standard books of reference on 

 plant physiology, such as those of Sachs, Pfeffer, Strasburger, 

 Darwin, Francis Darwin, Vines, and Detmer. 



In analysing plant-movements the greatest complexity 

 arises from the confusion of effects due to internal energy 

 and external stimulus respectively. I have, however, been 

 able to discriminate the characteristic expressions of these 

 two factors, and thus to disentangle the complex phenomena 

 which result from their combined action. Another very 

 obscure problem is found in the nature of so-called ' spon- 

 taneous or autonomous ' movements. By the discover}', 

 however, of multiple response, and by the continuity which I 

 have been able to establish, as existing between multiple and 

 autonomous responses, it has been found possible to demon- 

 strate that there are, strictly speaking, no ' spontaneous ' 

 movements, those known by this name being really due to 

 external stimulus previously absorbed by the organism. 

 Thus all the experiments ha\e tended to show that the 

 phenomenon of life does not, as such, connote any intrusion 

 into the realm of the organic of a force which would interfere 

 with that law of the Conservation of Energy which is known 

 to hold good in the inorganic world. 



The elucidation of the fact that such varied and obscure 

 phenomena in the life-processes of the plant, as, for instance, 

 growth and the ascent of sap, are fundamentally due to the 

 same excitatory reactions as are seen otherwise exemplified 

 in the simple mechanical response now familiar to us, con- 

 stituted a further result which, at the outset of the investiga- 

 tion, was little to be foreseen. 



