35^ PLANT RESPONSE 



Certain reagents tend to make irregular pulsations in 

 Desmodium regular. Conversely, other reagents, like barium 

 salts, induce irregularity in regular pulsations. The irre- 

 gularity induced by the latter reagent may, however, be 

 counteracted by a rise of temperature. 



The effects of acids and alkalis on the pulsatory move- 

 ments of Desmodium are antagonistic, acids inducing arrest 

 of pulsation in a relaxed position, while alkalis induce 

 its arrest in a contracted position. The standstill induced 

 by one reagent may therefore be counteracted by the use of 

 the other. 



By all these, the rhythmic phenomena of the plant are 

 seen to be identical with those of the animal. 



The pulsation of the animal heart is thus to be ascribed 

 to the same causes as bring about and maintain the rhythmic 

 pulsations of Desmodium. 



