I40 



PLANT RESPONSE 



each method furnishes a remarkable corroboration of the 

 other. I shall now proceed to describe these various results. 

 As an effect of low temperature I have found, by the use 

 of the electrical method, that response undergoes a very 

 great diminution. For example, the subjecting of a petiole 

 o{ Eucharis Lily to a temperature of —2° C. almost abolished 



its excitability (fig. 75). 

 (^^) \ ^ When the specimen, 



however, was restored to 

 the normal temperature 

 the original response 

 reappeared, and some- 

 times with even greater 

 amplitude than at first. 



When the plant is 

 maintained at a very low 

 temperature for a con- 

 siderable length of time, 

 the normal electrical 

 response disappears al- 

 together, and the spe- 

 cimen undergoes per- 

 manent death. In this 

 respect, different species 

 of plants have charac- 

 teristic powers of resist- 

 ance. For example, the 

 tropical plant, EiicJiaris 

 Lily, after an exposure 

 of twenty-four hours to 

 a temperature of 0° C, 

 on being subsequently restored to its normal temperature, 

 gives no sign of revival by response ; whereas the hardier 

 Holly and Ivy, when subjected to the same treatment, do 

 exhibit signs of renewed life (fig. 76). 



{b) Prolongation of latent period, or abolition of lateral 

 and autonomous responses. — Turning now to mechanical 



ih) 



Fig. 75. Diminution of Response in Eucharis 



Lily by Lowering of Temperature 

 {a) Normal response at 17° C. 

 {b) The response almost disappears when plant 



is subjected to -2° C. for fifteen minutes. 

 {c) Revival of response on warming to 20° C. 



