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CHAPTER IV 
ELECTRIC RESPONSE IN PLANTS—BLOCK METHOD 
Method of block—Advantages of block method—Plant response a physio- 
logical phenomenon—Abolition of response by anesthetics and poisons 
—Apbolition 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- 
