THERMONASTIC PHENOMENA 



311 



arrow ; the response is seen to be by a movement of 

 opening. Here also we find the etlects of rise of temper- 

 ature and of stimulus to be antagonistic to each otber. 

 This will be clearly seen in the foUowini^ tabular state- 

 ment. 



TABLK XXIX. — SHOWINCJ THE EFFECT OK RISE OF TEMPERATURK AND 

 OF STIMULUS ON THERMONASTIC ORGANS. 



In NymjjJicea it is the outer side of the perianth that 

 is relatively the more excitable since diffuse electric 

 stimulus induces a movement of opening due to the 

 greater contraction of the outer side. It is by the greater 

 expansion of this more excitable side that the movement 

 of closure is effected during rise of temperature. 



From the results of experiments given above we arrive 

 at the following : — 



LAW OF THERMONASTIC REACTION 



RISE OF TEMPERATURE INDUCES A GREATER EXPANSION 

 OF THE MORE EXCITABLE HALF OF AN ANISOTROPIC ORGAN. 



SUMMARY. 



Thermouastic movements are induced by the differen- 

 tial physiological effect of variation of temperature on the 

 two halves of an anisotropic organ. 



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