98 A. B. Ploioman — Electromotive Force in Plants. 



an electrical disturbance, can hardly be questioned. That an 

 electrical shock of slight intensity is capable of exciting the 

 protoplasm is equally certain. Apparently the separation of 

 impulse transference, electromotive force, and protoplasmic 

 response is a difficult problem. If the rate of transfer could 

 be measured accurately it would probably offer a solution. 

 But this, independently of the time of protoplasmic response, 

 has not been measured. 



The spreading of an electric current to all parts of a leaf 

 through which it is flowing, and the distribution of the reac- 

 tion current which follows, may be shown by simple experi- 

 ments to be precisely analogous to the similar phenomena in 

 non-living bodies. 



r 



\ 





Fig. 3- 



N/50 WaCl. 







omin. 



1 ""- 



—— ft 



3 4 



5 



6 



7 













Fig. 1 represents a rectangular piece of filter paper which 

 was saturated with N/50 NaCl, and through which a lv. *1 

 amp. current was passed between the points marked + and — . 

 With galvanometer terminals l cm apart, the entire field was ex- 

 plored on the lines B, C, D, . . . H. The potential difference 

 in each case is recorded on the line joining the points of contact, 

 and in units of 1 X 10" 3 volt. After the battery current was 

 turned off, the field was again explored and recorded in the 

 same units, fig. 2. Values less than unity are not recorded. 

 At no part of the field was the potential difference impercep- 

 tible with a galvanometer sensitive to 1 X 10" 6 volt. Of course 

 the current flowed in the same direction through the galva- 

 nometer as before, since it passed in the opposite direction 

 through the paper. (We are inclined to believe that Sander- 

 son was in error on this point in some cases.) From this well- 

 known tendency of the electric current to spread over the entire 

 conductor, it seems quite possible that electrical stimulation of 

 one lobe of Dionsea may spread, as an electrical disturbance, to 

 the other lobe. 



The generation of E.M.F. by diffusion and difference of con- 

 centration is shown graphically in Hg. 3. In this and the fol- 

 lowing figures the unit potential is 1 X 10" 5 volt. Potential 

 differences are always represented by vertical displacement of 

 the curve, while time units are plotted on the horizontal axis. A 

 piece of filter paper 10 cra square was rolled tightly, and the pla- 

 tinum-wire terminals of the galvanometer were inserted in the 



