EFFECT OF CHEMICAL AGENTS 



333 



The result also is dependent on the tonic condition of the 

 tissue. A specimen in which the amplitude of pulsation is 

 the maximum possible cannot exhibit any further increase 

 under a stimulating agent. But with a less vigorous spe- 

 cimen the effect of the same agent is manifested by a marked 



Fig. 176. — Stimulating action of dilute sugar solution applied 

 at the moment marked by an arrow. 



enhancement of amplitude of pulsation. Again, a vigorous 

 plant may survive a given dose of a toxic agent ; while a 

 less vigorous specimen will succumb under the same treat- 

 ment. Finally we have the interesting phenomenon in 



Fig. 177. — Effect of external application of alcohol. Preliminary 

 enhancement followed by depression, the period of pulsation 

 being prolonged. 



virtue of which the plant accommodates itself to a changed 

 unfavourable condition. 



Certain chemical agents act as stimulants, inducing an 

 enhancement of amplitude of pulsation. As an example of 



