328 PLANT RESPONSE 



The effect of a reagent depends also on the strength of 

 the solution. A reagent which, in strong solution, induces 

 depression, may, if given in small quantities, cause exalta- 

 tion. 



The effect of a reagent depends also on the duration of 

 application. The temporary depression produced by a short 

 application is overcome by the self-accommodation of the 

 plant. But it will succumb to too long or too strong an 

 application of the same reagent. 



The effects of the various reagents on autonomous response 

 are, generally speaking, similar to their effects on simple 

 response. 



The depressed position of the leaflet of Desmodium 

 represents a ' systolic ' contraction, and the up position a 

 1 diastolic ' relaxation, of the motile organ. Increased internal 

 hydrostatic pressure increases the extent of the relaxed or 

 ' diastolic ' limit. 



The effect of too strong an application of ether is to 

 abolish response, the arrest of pulsation usually taking place 

 in a relaxed position. The immediate effect of application is 

 generally a transient exaltation of response. 



The effect of vapour of alcohol is usually a transient 

 exaltation. If the application be prolonged, the result is a 

 permanent arrest of pulsation. 



Carbonic acid sometimes produces a transient exaltation 

 of response, and always a subsequent depression, which, 

 under the long-continued action of this gas, may pass into 

 permanent arrest. 



Copper sulphate solution, when applied directly on the 

 pulvinus, quickly causes arrest of pulsation ; but if the cut 

 petiole be allowed to absorb the solution, the final arrest 

 does not take place till after the lapse of a certain period, 

 required for the solution to ascend to the motile organ. 



