Siiggestion of Siegfried. 159 



The subject is clearly one which interested van't Hoff deeply, 

 as is seen from his letters and diary (Cohen, 1912), and he intended 

 to subject the pi'oblems to an extensive investigation. Bad health, 

 and finally death, prevented him from carrying out this project, 

 and we only possess fi-om his hands two papers on the subject 

 (1909, 1910) entitled " On Synthetic Enzyme Action," neither of 

 which is of interest here. 



Van't Hoff's suggestion obtains a new interest in view of 

 Willstatter's discovery that chlorophyll is a double ester of two 

 primary alcohols, and that leaves contain an enzyme which can 

 effect hydrolysis or alcoholysis of chlorophyll, and can also 

 synthesize chlorophyll from phytol and chlorophyllid (Willstatter 

 and Stoll, 1911, 1913). Unfortunately, as we have pointed out 

 earlier, Willstatter's contention that the amount of pigment is not 

 altered during assimilation, only holds for the chromogen complex, 

 and provides no information as regards the alcohol groups. 

 Therefore we have no indication whether chlorophyllase or the 

 alcohol groups play any part in the processes of carbon assimi- 

 lation. 



D. Suggestion of Siegfried. 



Siegfried (1905) worked on the action of carbon dioxide on 

 amino-acids and proteins, and came to the conclusion that definite 

 compounds, carbaminic acids and carbaminates are produced. 

 Thus he says that his residts " appear to justify the assumption 

 that where carbon dioxide meets protein in the animal organism, 

 carbon dioxide is fixed organically, and that the compounds so pro- 

 duced dissociate again with evolution of carbon dioxide." After 

 discussing the bearing of this conclusion on various processes in 

 animal physiology, such as blood processes, and the working of 

 muscle, he concludes : " Finally, plant physiology also will have 

 to concern itself with this question. Where there is chlorophyll 

 there is also protoplasm, if by the intake of carbon dioxide by 

 the plant carbamino groups are formed, the intake of carbon 

 dioxide will be accelerated. Instead of, or along with the question, 

 how is carbon dioxide reduced, the question must be solved, how 

 are carbon acids reduced." 



It will be seen that we have here a suggestion in regard to the 

 processes of carbon assimilation which differs markedly from 

 the Baeyer hypothesis. It is generally assumed that in the first 

 stage of the assimilatory process the carbon dioxide takes part in 



