Petiole- Pulvinus Preparations of Mimosa pudica. 225 



recovery incomplete. The sluggishness was so great that the next stimula- 

 tion, represented by a thick dot (fig. 8), was ineffective. Tetanising electric 











: 7 1 







v 









Fig. 8. — Incomplete recovery under the action of BaCl 2 and transient restoration under 



tetanisation at T. 



shock at T, not only brought about response, but removed for the time being 

 the induced sluggishness. This is seen in the next two records, which were 

 taken under the old test-stimulus. There is now an enhanced response and 

 a complete recovery. Beneficial effect of tetanisation disappeared, however, 

 on the cessation of stimulus. This is seen in the next two records, which 

 were taken after two hours. The amplitude of response was not only 

 diminished, but the recovery also was incomplete. 



Antagonistic Actions of Alkali and Acid. — Alkali and acid are known to 

 exert antagonistic actions on the spontaneous beat of the heart : dilute 

 solution of NaOH arrests the beat of the heart in systolic contraction, while 

 dilute lactic acid arrests the beat in diastolic expansion. I have found 

 identical antagonistic reactions in the pulsating tissue of Desmodium gyrans 

 (the telegraph plant). It is very interesting to find that these agents also exert 

 their characteristic effects on the response of Mimosa in a manner which is 

 precisely the same. This is seen illustrated in fig. 9, where the application 

 of NaOH arrested the response in a contracted state ; after this, the 

 antagonistic effect of dilute lactic acid is seen first, in its power of restoring 

 the excitability; its continued application, however, causes a second arrest, 

 but this time in a state of relaxed expansion. 



CuSOi Solution. — This agent acts as a poison, causing a gradual diminu- 

 tion of amplitude of response, culminating in actual arrest at death. Certain 

 poisons, again, exhibit another striking symptom at the moment of death, an 

 account of which will be given iu a separate paper. 



