140 



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 

 of EucJiaris Lily to a temperature of — 2° C. almost abolished 



its excitability (fig. 75). 

 (a ) \\ 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, Eucharis 

 Lily, after an exposure 

 of twenty-four hours to 

 a temperature of o° 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. y6). 



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

 and autonomous responses. — Turning now to mechanical 



(bj 



Vic. 75. Diminution of Response in Eucharis 



Lily by Lowering of Temperature 

 (a) Normal response at 17 C. 

 {(>) The response almost disappears when plant 



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

 (1 ) Revival of response on warming to 20 C. 



