PLANT RESPONSE 



61 



(17 C.). I then placed it for fifteen minutes in a cooling 

 chamber, temperature 2 C., for only ten minutes, 

 after which, on trying to obtain response, it was found to 

 have practically disappeared. I now warmed the plant 

 by immersing it for awhile in water at 20 C., and this 

 produced a revival of 

 the response (fig. 35). 

 If the plant be sub- 

 jected to low tempera- 

 ture for too long a 

 time, there is then no 

 subsequent revival. 



I obtained a simi- 

 lar marked diminution 

 of response with the 

 flower-stalk of Arum 

 lily, on lowering the 

 temperature to zero. 



My next attempt 

 was to compare the 

 sensibility of different 

 plants to the effect of 

 lowered temperatures. 

 For this purpose I 

 chose three specimens : 

 (1) Eucharis lily ; (2) 

 Ivy ; and (3) Holly. I took their normal response 

 at 17 C., and found that, generally speaking, they 

 attained a fairly constant value after the third or 

 fourth response. After taking these records of normal 

 response, I placed the specimens in an ice-chamber, 



FIG. 35. DIMINUTION OF KESPONSE IN 

 EUCHAKIS BY LOWERING OF TEMPERATURE 



(a) Normal response at 17 C. 



(b) The response almost disappears when plantfis 



subjected to -2 C. for fifteen minutes. 

 (r) Kevival of response 011 warming to 20 C. 



