Chap, xi Sensitivity and Stimulation 463 



careful electrical measurement he proved that electrical 

 changes of a similar nature to those attending the stimula- 

 tion of muscle or nerve follow the stimulus administered 

 to the receptive organs of the leaf, preceding by a measur- 

 able interval of time the turgor changes leading to its 

 closure. 



In a final paper, published in 1888, he criticized Sachs' 

 attitude and showed its weakness in that the latter did 

 not distinguish the molecular changes in the stimulated 

 protoplasm from the slow mechanism of growth, turgor- 

 change, or exudation of water, by which the excited proto- 

 plasm brought about the purposeful response. The differ- 

 ence is greater than at first it seems to be, for Sachs' 

 position involved if not the denial, at any rate the non- 

 recognition of the existence of anything of the nature of 

 a nervous mechanism in the plant, a view to which Burdon- 

 Sanderson had been led and on which he laid considerable 

 stress. Sachs said, indeed, ' we have no necessity to refer 

 to the physiology of nerves in order to obtain greater 

 clearness as to the phenomena of irritability in plants.' 

 To Sachs the electrical phenomena observed by Burdon- 

 Sanderson were the consequences of the disturbances of 

 the equilibrium of the water in the tissues, rather than 

 the accompaniments of the disturbance of the equilibrium 

 of the protoplasm. 



Burdon-Sanderson's researches were the last of the period 

 to carry towards elucidation the theory of the sensitiveness 

 of vegetable organisms. They helped perhaps more than 

 any others to establish the identity of the protoplasm of 

 animals and plants, and aided greatly to stimulate those 

 inquiries into nutrition, which have been already alluded to. 



Towards the latter part of the century valuable con- 

 tributions to the general subject came from the pens of 

 Stahl, Strasburger, Vochting, Rothert, Noll, and Czapek, 

 besides further memoirs from those already mentioned ; on 



