PREFACE vii 



even in the higher realms of science ' something more 

 grossly mechanical, a model, is felt by many to be more 

 suggestive and manageable, and for them a more 

 powerful instrument of research.* ... I really think 

 that some such models as those formerly proposed by 

 De Candolle for the heliotropic effect or by Hofmeister 

 for the elucidation of geotropism, adapted of course to 

 the growing exigencies of the time, might bring back 

 the study of the mechanism of growth to a more promis- 

 ing field of research. 



That the ideas I venture to advocate are not so 

 utterly out of date may be inferred from the fact that 

 similar ideas have been recently advanced by a repre- 

 sentative of a much younger generation of botanists, 

 by the regretted Professor Barnes. 1 For my part, I 

 am as firmly convinced as I was forty years ago that the 

 ' mechanistic conception ' and Darwinism have been 

 bequeathed by the ' wonderful century ' to the still 

 infant science of plant physiology as the two sure guides 

 for its further evolution, and I may adduce in support 

 of this opinion the eloquent testimony of the late 

 Professor Boltzmann : ' If I were asked, how will 

 our century be called by the coming generations the 

 century of iron, of steam, or of electricity? I would reply, 

 in all earnest, it will be called the century of the mechani- 

 cal interpretation of nature, the century of Darwin.' 2 



It is impossible for me to bring to a close this pre- 

 fatory notice without expressing my best thanks to 



1 ' In fact there is an inclination after endowing protoplasm with such 

 properties as " irritability," " automaticity," and " self-regulation," to be 

 satisfied with these words and there make an end.' ' I propose only to 

 present some suggestions on the matter of these phenomena as a con- 

 tribution towards a mechanistic conception of plant.' . . . The Nature of 

 Physiological Response. The Botanical Gazette, New York, 1910, pp. 322- 



323- 



2 Das zweite Hauptgesetz der mechanischen Warmetheorie, 1886. Populate 

 Schriften, von Professor Ludwig Boltzmann, 1905, p. 28. 



