86 Carbon Assimilation. 



E. Chlorophyll Content. 



So far we have dealt with environmental factors. It has been 

 seen from Blackman's analysis that the laws governing the intake 

 of carbon dioxide in relation to these factors cannot yet be expressed 

 in simple physical and chemical terms, but the expei'imental facts so 

 far obtained can be conveniently expressed in terms of the action 

 of limiting factors. 



Nor would it seem any more probable that an enquiry into the 

 relation between an internal factor, e.g., chlorophyll, and the intake 

 of carbon dioxide should yield results of any gi-eater physico- 

 chemical definiteness. In this section we shall deal in some detail 

 with investigations made with a view of determining the relation 

 between assimilation and chlorophyll content, and more particularly 

 with the recent work of Willstatter and Stoll (1915) At present 

 only preliminary accounts of the extensive work of these investigators 

 are available ; consequently it is difficult to form a correct judgment 

 of the value of the work and the validity of the arguments put 

 forward in support of the hypotheses advanced. 



There is a strong contrast between Willstatter's and Blackman s 

 expi'ession and generalisation of experimental results. While 

 Blackman carefully avoids premature conclusions and tries to find 

 non-committal expressions which will embody all his experimental 

 results, Willstatter advances a simple definite hypothesis and 

 attempts to obtain experimental data which will support his theory. 



In this section we shall only give Willstatter's experimental 

 data, in a later chapter we shall deal with the various theories of 

 carbon assimilation which he has advanced. 



The main result of his work is a demonstration of the complexity 

 of the processes of carbon assimilation ; an opinion which has often 

 been expressed by earlier workers. For instance Pfeffer (1897) 

 says that the chloroplasts "are only capable of assimilatory activity 

 when all the component parts co-operate in an appropriate manner, 

 and that the final result is produced not by a single reaction but by 

 the agency of a complicated and self-regulatory mechanism." 



Ewart (1896, 1897) and Pantanelli (1903) have published data 

 which also tend to show that chlorophyll is not the only internal 

 factor in the processes of carbon assimilation. 



