Chlorophyll Content. 



89 



Expressiiifj this in terms of Blackman's principle it must mean 

 that neither light noi' carhon ilioxide is a limiting factor. The 

 amount of carhon dioxide assimilated can then only depend on 

 internal factors and the temperature. 



The ratio hetween the quantity of chlorophyll and the 

 carhon dioxide assimilated in a certain time is termed hy 

 Willstatter the assimilation numher (assimilation number = 

 amount of €0^ assimilated in one hour. ^ 

 chlorophyll content. ' 



Approximately constant values of the assimilation number 

 would indicate that the assimilation depended only on the amount 

 of chlorophyll, if variable values are obtained it means that other 

 factors come into play. 



It is to be regretted that only the tables which illustrate the 

 conclusions are given hy Willstatter; none of the preliminary work 

 necessary for the justification of the conclusions is quoted. 



Normal Leaves. 



In Table XV we give the results obtained by Willstatter for 



normal leaves. 



Table XV. 



Assimilation Numbers of Normal Leaves. 



Concentration of CO^i 5%. 



Rate of Gas Current, 4'5 litres per hour. 



From the numbers given in this table there would seem to be 

 a rough parallelism between the amount of chlorophyll and 

 assimilation. But in all the cases given the leaves were in the 

 same stage of development and all were rich in chlorophyll. On 

 the other hand leaves from the same plant, but in different stages 

 of development, exhibit much wider variations in the assimilation 

 number, as the following table shows. 



