PLANT RESPONSE 



(say 17 C.), was mounted in the vibration apparatus arid 

 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 EFFECT OF HIGH TEMPEKATTJKE IN 

 ABOLISHING RESPONSE 



Temperature 



Electric heating. The 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 



