68 RESPONSE IN THE LIVING AND NON-LIVING 



gives a curve of variation 



of temperature. Fig. 41 



of response during the rise and fall of temperature. 



Point of temperature maximum. We have seen 

 how, in cases of lowered temperature, response is 

 abolished earlier in plants like Eucharis, which are 

 affected by cold, than in the hardier plants such as 

 Holly and Ivy. Plants again are unequally affected as 

 regards the upper range. In the case of Scotch kale, 

 for instance, response disappears after ten minutes of 

 water temperature of about 55 C., but with Eucharis 

 fairly marked response can still be obtained after such 



20C 



60C. 



FIG. 41. CURVE SHOWING VAKIATION OF RESPONSE IN EUCHARIS WITH THE 

 RISE AND FALL OF TEMPERATURE 



immersion and does not disappear till it has been sub- 

 jected for ten minutes to hot water, at a temperature 

 of 65 C. or even higher. The reason of this great 

 power of resistance to heat is probably found in the 

 fact that the Eucharis is a tropical plant, and is grown, 

 in this country, in hot-houses where a comparatively 

 high temperature is maintained. 



The effect of steam. I next wished to obtain a 

 continuous record by which the effects of suddenly 

 increased temperatures, culminating in the death of the 

 plant, might be made evident. For this purpose I 

 mounted the plant in the glass chamber, into which steam 



