68 RESPONSE IN THE LIVING AND NON-LIVING 
of temperature. Fig. 41 gives a curve of variation 
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 


Fie. 41.—CurvE sHowING VARIATION oF RESPONSE IN EUCHARIS WITH THE 
RisE AND Fay or 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 
