244 



SMITH 



is one important respect, however, in which thick succulent 

 leaves differ from thin leaves in their absorption of radiation, 

 and that is with regard to the time taken to attain the maxi- 

 mum temperature after exposure. The following experiments 

 bear upon this point : — 



1 

 Time. 



A.M. 



9.27 

 9.28 

 9.30 

 9.32 

 9.34 

 9.42 

 9.50 



Table XV.— January 25, 1906. 



Leaf of Rhoeo discolor. 

 2 3 4 



Conditions. 



In full sun 

 Shaded 



Do. 



Do. 



Do. 



Do. 



Do. 



Shade air 

 Temperature. 



25-5 



25-6 

 25-6 

 25-6 



25-8 

 25-8 



Leaf 

 Temperature. 



37-2 



31-5 

 29-4 

 28-6 

 27-5 

 27-4 



.5 



Difference 



between 



3 and 4. 



11-7 



5-9 

 3-8 

 30 

 1-7 

 1-6 



Table XVI.— January 25, 1906. 



