Vlll PREFACE 



' Plant Response ' (1906) I stated that the aim of my work was 

 the demonstration of the unity of physiological mechanism 

 of the plant with that of the animal, as evidenced by the 

 script of the plant, and not the 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. 



My investigations were commenced with the study of 

 the mechanical response given by plants to stimulation 

 (' Plant Response,' 1906). Since then they have been greatly 

 extended by instrumental appliances of extraordinarily 

 high magnification, the employment of which at one time 

 created some misgiving that the records obtained might be 

 due to physical disturbance and not to physiological reac- 

 tion. It would be an unpardonable omission of any investi- 

 gator to fail to take complete precautions against all possible 

 purely physical effects. The obvious method is to perform 

 parallel experiments with two plants, one of which is alive 

 and the other dead. The vigorous response of the living 

 plant, contrasted with complete absence of all response in the 

 dead, gives conclusive evidence in regard to the physiological 

 character of the reaction. This test has been carried out 

 by competent authorities, who reported [Nature, May 6, 

 1920) that my Magnetic Crescograph, with its magnification 

 of one to ten million times, gives correct record of what is 

 undoubtedly the physiological response of the plant. 



The results obtained by the method of mechanical 

 response were confirmed in every detail by the method of 

 electric response, the essential feature of which is the 

 negative electromotive variation which is caused by stimu- 

 lation. In my ' Comparative Electro-Physiology ' (1907) 

 special precautions were enjoined for avoiding the errors 

 into which investigators are likely to fall in the employment 

 of these powerful aids to investigation. 



I have in this, and in my previous works, employed 

 several independent methods of experimentation, whose 



