CHAPTEE IV 



ELECTRIC RESPONSE IN PLANTS BLOCK METHOD 



Method of block Advantages of block method Plant response a physio- 

 logical phenomenon Abolition of response by anaesthetics and poisons 

 Abolition of response when plant is killed by hot water. 



I SHALL now proceed to describe another and inde- 

 pendent method which I devised for obtaining plant 

 response. It has the advantage of offering us a com- 

 plementary means of verifying the results found by the 

 method of negative variation. As it is also, in itself, 

 for reasons which will be shown later, a more perfect 

 mode of inquiry, it enables us to investigate problems 

 which would otherwise have been difficult to attempt. 



When electrolytic contacts are made on the un- 

 injured surfaces of the stalk at A and B, the two points, 

 being practically similar in every way, are iso-electric, 

 and little or no current will flow in the galvanometer. 

 If now the whole stalk be uniformly stimulated, and 

 if both ends A and B be equally excited at the same 

 moment, it is clear that there will still be no responsive 

 current, owing to balancing action at the two ends. 

 This difficulty as regards the obtaining of response was 

 overcome in the method of negative variation, where 

 the excitability of one end was depressed by chemical 

 reagents or injury, or abolished by excessive tempera- 



