74 



Carbon A ssimilation. 



Assimilation at High Temperatures. 



It is thus possible to construct a curve showing the relation 

 between temperature and assimilation when neither light nor carbon 

 dioxide supply is a limiting factor. Above 25"C, however, a fresh 

 complication arises. Below 25"C the amount of assimilation 

 remains constant hour after hour, but above this temperature the 

 rate of assimilation decreases with time. The initial rate of 

 assimilation cannot be maintained. In all the experiments the rate 

 of assimilation during the first 1| hours was not measured ; 

 measurements were then made of the assimilation taking place in 

 successive hours. Finally the leaf was darkened and the respiration 

 measured. The following tables show typical series of results for 

 the assimilation of the leaf at a low temperature and at a high 

 temperature during successive hours. 



Table XI. 



Assimilation of Leaf of Cherry Laurel at S-S'C. 



Area of Leaf 44-6 sq. cms. 



Table XII. 

 Assimilation of Leaf of Cherry Laurel at 37-5"C. 

 Area of Leaf, 36-0 sq. cms. 

 Respii^ation, 0-0019 grams pei^hour. 



