CHAPTER XXXII 



ELECTRICAL RESPONSE OF ISOLATED VEGETAL NERVE 



Specialised conducting tissues Isolated vegetal nerve Method of obtaining 

 electrical response in vegetal nerve Similarity of responses of plant and 

 animal nerve: (a) action of ether (l>) action of carbonic acid (c) action 

 of vapour of alcohol (d) action of ammonia (<?) exhibition of three types 

 of response, negative, diphasic and positive (/) effects of tetanisation of 

 normal and modified specimens Effect of increasing stimulus on response 

 of modified tissue. 



IT has been shown in the previous chapter that the state of 

 excitation is transmitted to a distance in vegetable tissues. 

 It has also been proved that such transmission is not due to 

 the propagation of hydrostatic disturbance but to that of 

 protoplasmic changes, precisely as in the case of animal 

 tissues. It is obvious, further, that such transmission will be 

 the more perfect the less the interruption of protoplasmic con- 

 tinuity. Hence tissues like stems and petioles, which contain 

 fibro-vascular elements, are found to be good conductors 

 of excitation, whereas indifferent tissues, such as those of 

 leaves and tubers, are relatively feeble as regards this power, 

 excitation in their case remaining somewhat localised. 



Even with regard to stems and petioles themselves, a 

 contrast is found to exist in this respect between the fibro- 

 vascular elements and the ground tissue. Thus, in the case 

 of a petiole of cauliflower, I made two experimental prepara- 

 tions. In the first, the ground tissue was cut away, leaving 

 the fibro-vascular elements ; and in the second, a column of 

 ground tissue was left outstanding, denuded of fibro-vascular 

 elements. The former of these was found to transmit 

 excitation to a certain distance, whereas in the latter the 

 transmission was practically absent. In the case of a third 



