GBO-ELECTRIC RESPONSE OF ROOT 



473 



the geotropic stimulation six times in succession, the 

 results being perfectly consistent. The responses taken 

 in succession exhibited slight fatigue, the first deflection 

 being 140 divisions, and the sixth 115 divisions of the 

 galvanometer scale. 



TAUI.K XXXIX. — INDUCED E. M. V. VARIATION BETWEEN THE TIP AND 

 THE GBOWING REGION (a NEGATIVE AND A POSITIVE). 



The results of experiments 182 and 183 are summarised 

 as follows : — 



(1) the induced galvanometric negativity at root tip 



indicates direct stimulation of the tip, and 



(2) the induced galvanometric positivity of the grow- 



ing region shows that it is the effect of indirect 

 stimulus that reaches it. 



From these facts it will be seen that the tip per- 

 ceives the stimulus and thus undergoes excitation, and that 

 owing to the intervening tissue being a semi-couductor 

 of excitation, it is the positive impulse that reaches the 



35 A 



