9S ox THE TR.VXSiMR.VTIOy OF PLAXTS. 



B. Y. G. B. V. CL 



•261 -213 -204 '265 -2G3 -274 



la this case the transpiration, as is well known, is slight, in con- 

 Bequence of the thick cuticle. I have therefore taken it to 

 tliree places of decimals ; but here, again, yellow gives a decided 

 minimum, and clear glass the highest maximum, the other 

 maxima being but slightly differeut fi^om each other. 



Conclusion". — The above experiments, selected from a large 

 series, seem to me to abundantly prove that Wiesner's results 

 are correct ; and while recognizing the fact that obscure heat-rays 

 cause a certain amount of the loss of water by evaporation, that 

 transpiration p^r se (theoretically distinct from the purely phy- 

 Bical process of evaporation, which takes place from all moist 

 surfaces and bodies, dead or alive) is especially, if not solely, 

 referable to those particular bands of light v/hich are absorbed by 

 chloi'ophyll, and that such light, being arrested, is converted into 

 heat, which then raises the temperature within the tissues and 

 causes the loss of water. The only additional fact which I have 

 here advanced, somewhat tentatively, is that yellow light has a 

 retarding i7ijluence upon transpiration, for the reasons given above. 

 That ''life " has a retarding influence upon evaporation as distinct 

 from transpiration, I think my experiments (which I hope to 

 continue hereafter) have distinctly proved. 



