TEMPERATURE ON PHOTOTROPIC CURVATURE 



395 



cessation of light (Fig. 1471)). This reversal of response as an 

 after-effect of rise of temperature was in this case found to 



Fig. 1-47. — After-effecc of rise of temperature, persistent negative curvature : (a) 

 response one hour after rise of temperature; (.6) series of negative responses after 

 4 hours (successive stimuli applied at vertical lines). 



persist for several hours. I experimented with the same speci- 

 men next day when the response was found restored to the 

 normal positive. 



SUMMARY. 



Rise of temperature, within limits, enhances the general 

 excitability of the organ. This has the effect of increasing 

 positive phototropic curvature. But the physiological expan- 

 sion induced by rise of temperature exerts an antagonistic 

 effect. 



The transverse conductivity is increased with the rise of 

 temperature ; this favours neutralisation and reversal of photo- 

 tropic curvature. 



Tendrils of Passifiora, supposed to be phototropically 

 insensitive, exhibit positive curvature at low, and negative cur- 

 vature at a moderately high temperature. 



