PLANT KESPONSE 69 
could be introduced. I had chosen a specimen which 
gave regular response. On the introduction of steam, 
with the consequent sudden increase of temperature, 
there was a transitory augmentation of excitability. 
But this quickly disappeared, and in five minutes the 
plant was eflectively killed, as will be seen graphically 
illustrated in the record (fig. 42). 

Before 
“N After 
Fic. 42.._Errect or Steam 1n Kitiinac REsPoNsE 
The two records to the left exhibit normal response at 17°C. Sudden warming 
by steam produced at first an increase of response, but five minutes’ expo- 
sure to steam killed the plant (carrot) and abolished the response. 
Vibrational stimulus of 30° applied at intervals of one minute; vertical 
line='1 volt. 
It will thus be seen that those modifications of vital 
activity which are produced in plants by temperature 
variation can be very accurately gauged by electric 
response. Indeed it may be said that there is no other 
method by which the moment of cessation of vitality 
can be so satisfactorily distinguished. Ordinarily, we 
