INTERNAL TEMPERATURE OF LEAVES. 



245 



If from these tables curves of the fall or rise of temperature 

 with the time are plotted, it will be seen that, in the case of 

 this succulent leaf, at least ten minutes must pass after 

 exposure or shading before the leaf takes up the temperature 

 corresponding to the new conditions. For comparison with 

 this the following results with thinner leaves are given : — 



Table XVII.— January 22, 1906. 

 Magnolia spheriocarpa. 



Difference. 



2-3 



70 

 11-5 

 17-0 



131 

 71 

 5-6 

 3-6 

 3-6 



In this case we find that in three minutes after shading or 

 exposure the leaf takes on the temperature corresponding to 

 the new conditions. 



Table XVIII.— January 27, 1906. 



Acalypha tricolor. — Variegated leaf. — Junction 

 in green part. 



