1888.] Electromotive Properties of the Leaf of Dionaea. 203 



current " of the leaf, i.e., between the electrical properties possessed 

 by the leaf when stimulated, and those which it displays when at 

 rest. Assuming the excitatory response in the leaf to be of the same 

 nature as the excitatory variation or " action current " in muscle and 

 nerve, the question has to be answered, whether in the leaf the 

 response is a sudden diminution of a previously existing electromotive 

 action (according to the pre-existence theory of du Bois-Reymond), 

 or the setting up at the moment of stimulation of a new electromotive 

 action — in short, whether and in how far the two sets of phenomena 

 are interdependent or the contrary. 



An observation recorded in his former paper suggested proper 

 methods. It had been shown that by passing a weak voltaic current 

 through the leaf for a short period in a particular direction, its 

 electromotive properties could be permanently modified without loss 

 of its excitability. If it could be shown that the influence of this 

 modification extended to* both orders of phenomena, those of rest and 

 of excitation y and that both underwent corresponding changes of 

 character under similar conditions, this would go far to prove that 

 an essential relation existed between them. 



Acting on this suggestion,, the author has had recourse to modes 

 of experiment similar to those which have been employed during 

 the last few years in the investigation of the newly-discovered 

 " secondary electromotive " phenomena of muscle and nerve (see 

 ' Oxford Biological Memoirs,' vol. 1, part 2). The details of these 

 expeiiments, made in 1885, are given in the first three sections of the 

 paper. They relate to (1) the more immediate effect of the current as 

 seen in the records of successive galvanometric observations made at 

 regular intervals * (2) the more permanent influence of the current on 

 the electromotive properties of the unexcited leaf, and on its electrical 

 resistance ; and (3) the concomitant modification of its behaviour 

 when stimulated. 



The general result of these experiments is to show that the two 

 orders of phenomena, the excitatory and those which relate to the 

 resting state, are so linked together that every change in the state of 

 the leaf when at rest conditionates a corresponding change in the 

 way in which it reacts to stimulation — the correspondence consist- 

 ing in this, that the direction of the response is opposed to that of the 

 previous difference of potential between the opposite surfaces, so that 

 as the latter changes from ascending to descending, the former 

 changes from descending to ascending. 



The author considers that this can only be understood to mean 

 that the constantly operative electromotive forces which find their 

 expression in the persistent difference of potential between the 

 opposite surfaces, and those more transitory ones which are called 

 into momentary existence by touching the sensitive filaments or by 



