350 RESEARCHES ON IRRITABILITY OF PLANTS 



place at the make and break of both kathode and 

 anode. 



Physiological changes are also found to modify the 

 polar effects of current. Under the separate or joint action 

 of an increasing current and physiological modification, 

 types of reaction are observed in plants which are similar 

 to the so-called anomalous response in Protozoa (p. 276). 



Contrasted Effects of Anode and Kathode 



In the animal heart the contrasted effects of anode and 

 kathode are exhibited by characteristic modification of its 

 pulsating activity. Effects precisely similar are shown in 

 the rhythmic tissue of Desmodium gyrans. The effect of 

 the make of anode is to induce an expansion ; this is shown 

 in the record of pulsation of Desmodium by a reduction of 

 normal limit of systolic contraction. The opposite effect 

 of contraction due to the make of kathode is seen in the 

 reduction of normal limit of diastolic expansion (p. 236). 



In nerve-and-muscle preparation the effects of ascending 

 and descending currents are found to be modified by the 

 intensity of the current. Effects in every way parallel are 

 observed in experimenting with petiole-pulvinus of Biophy- 

 tum. These characteristic modifications are easily trace- 

 able in Biophytum to the contrasted effects of anode and 

 kathode and of make and break. Excitability is enhanced 

 by the make of kathode and break of anode. It is 

 depressed by the make of anode and break of kathode 

 (P- 239)- 



A very important problem in plant physiology relates 

 to the question as to whether in plants there is any trans- 

 mission of true excitation. The prevailing opinion has 

 been that in plants like Mimosa pudica there is merely a 

 passage of hydro-mechanical disturbance, unlike the trans- 

 mission of excitatory protoplasmic change, which takes 

 place in an animal nerve. This view has been based on 



