258 RESEARCHES ON IRRITABILITY OF PLANTS 



excitation to occur at make. The kathode was then broken 

 suddenly, with the result that excitation was immediately 

 exhibited. Hence the kathode-break effect under strong 

 current must be taken as a normal phenomenon. 



I have carried out more than fifty different sets of experi- 

 ments on the characteristic effects of relatively strong 

 currents, which have fully confirmed the results described. 

 It was uniformly found that as the current was increased 

 step by step, the transformation took place, as here laid 

 down, to a higher type, and never consisted of reversion 

 to a lower. 



Taking these facts, then, as well established, the question 

 arises whether the new, and apparently anomalous, effects 

 cannot be explained in a simple way as a special case of these 

 reactions with which we are already familiar ? Thus the first 

 explanation that occurred to me was that the fall of the 

 leaf at anode-make might be due to the arrival of excitation 

 at the anode from the distant kathode. Against this sup- 

 position, however, was the fact that a strong anode is known 

 to be so depressing as to act as a block to the arrival of any 

 excitation from outside. Overlooking this difficulty, the 

 arrival of excitation from a very distant kathode on a 

 different branch of the plant might be expected to take a 

 certain interval of time. But in the cases given, the excita- 

 tion at make of anode was, to all seeming, instantaneous. 

 Finally, I killed a point on the distant branch by severe 

 scorching, and made it kathode. By this means the possible 

 excitatory effect at kathode was completely eliminated. 

 In spite of this abolition of kathodic action, however, the 

 excitation at anode-make continued to take place as before. 

 Another modification of the experiment lay in previously 

 killing the end of the petiole whose pulvinus was being 

 experimented on. This was done, as before, by scorching. 

 The intense excitation caused by this injury induced an 

 excitatory action at the pulvinus, and it was only after 

 the expiration of about an hour that the organ regained its 

 excitability, and not even then to the fullest extent. The 



