9i 



Carbon Assimilation. 



Some leaves which remain green until they fall off keep their 

 assimilatory power, so that in spite of the lateness of the season 

 and high chlorophyll content, the assimilation numbers are still 

 high. Yet in other cases where the chlorophyll content of the 

 leaves in autumn is still high the assimilation numbers are remark- 

 ably low, while there is a considerable difference between the 

 assimilation numbers of young and old leaves from the same plant. 

 These results are given in Tables XX and XXI. 



Table XX. 



Autumn Leaves with high Chlorophyll Content and 



Normal Assimilation Numbers. 



Table XXI. 



Autumn Leaves with same Chlorophyll Content but 

 different Assimilation Numbers. 



The low assimilation number after exposure to low temperatures 

 is rapidly increased on exposure to higher temperatures. Thus in 

 the case of leaves of Ampelopsis Veitchii gathered at 4^0 the 

 assimilation number gradually increased from less than 0*8 to 2-6 . 

 after 1 J hours at 25"C, and increased up to about 4 when it remained 

 constant. 



