PLANT RESPONSE 63 
(say 17° C.), was mounted in the vibration apparatus and 
responses observed. The plant was then dismounted, 
and replaced in the water-bath at a higher temperature 
(say 30° C.) again, for five minutes. A second set of 
responses was now taken. In this way observations 
were made with each specimen till the temperature at 
which response almost or altogether ceased was reached. 
I give below a table of results obtained with six speci- 
mens of radish, from which it would appear that response 
begins to be abolished in these cases at temperatures 
varying from 53° to 55° C. 
TABLE SHOWING EFrrect oF High TEMPERATURE IN 
ABOLISHING RESPONSE 
Temperature Galvanometric response | Temperature Galvanometric response 
(100 dns. = *07 V.) | (100 dns. = ‘07 V.) 
Mijea es 7 Olans; | ACC anes 80 dns. 
Q) tage... hes: | Ora Oh 
° | [yde) 
Peel ....,..160° ,, | Pi leer dO 
(Oe ‘gee | Orig (ibe 
Alzert.<:.100 ~,, | =A alicne tee 60: 45 
5p |... aed | CO Ree Oi. 
Electric heating.—Ihe experiments just described 
were, however, rather troublesome, inasmuch as, in 
order to produce each variation of temperature, the 
specimen had to be taken out of the apparatus, warmed, 
and remounted. I therefore introduced a modification 
by which this difficulty was obviated. The specimen 
was now enclosed in a glass chamber (fig. 37), which 
also contained a spiral of German-silver wire, through 
which electric currents could be sent, for the purpose 
of heating the chamber. By varying the intensity of 
the current, the temperature could be regulated at will. 
The specimen chosen for experiment was the leaf-stalk 
of celery. It was kept at each given temperature for 
