ELECTRICAL PHENOMENA AND METABOLISM OF ARUM SPADICES. 473 



classification. The results obtained, as also consideration of the necessity 

 of postulating some means of interaction between the various parts of a 

 plant, enabling it to react as an organic whole to external and internal 

 stimuli — again, the existence of such adaptations to environmont as are 

 shown in the trophic reactions common to all plants, and in the rather 

 specialised cases of response to tactile stimuli in climbers — lead to the 

 conclusion that the power of propagating excitation, far from being 

 a rare and specialised phenomenon in vegetable tissues dependent on 

 special fibrillar structures, is innate in every normal cell, and occurs 

 freely wherever the protoplasmic continuity between cell and cell is at 

 all considerable. 



Transmission in Plants. — Selected Photos. 



PLATE T. 



Experiment 1. — Mvstard seedling (November 38, 1907). 



^ 



fACw. 



f\ 



(5 Cm. 



B 



Two successive ' diphasic ' responses to thermic excitation. Duration of double 

 phase = 2 min., distance = 3 cm. The two interpolated smaller deflections are by 

 ^ volt sent to the preparation. 



N.B. — The reader is advised that the records are taken (and reproduced) so that 

 current from A to B gives deflection to the right, and current from B to A deflection 

 to the left, in accordance with the diagram given below Exp. 1. 



The letter B on the photograph indicates that B is ' zincative ' ( = galvanometricaUy 

 negative to A). The letter A indicates tl at A is zincative to B. All other records 

 are taken on the same plan, i.e., deflection to the left indicates action at B, deflection 

 to the right action at A. — {A . B. ir.) 



