BACTERIA AND ENZYMES IN AGRICULTURE 267 



Sucli a reverse change would not take place in plants, inas- 

 snuch as the products of the first reaction, formaldehyde and 

 oxygen, are eliminated, the formaldehyde being utilised for 

 building up carbohydrates, and the oxygen passing off. 



We have still here to do with chlorophyll, a substance 

 elaborated by life processes. Experiments by Fenton in 

 1907 have, however, shown that carbon dioxide can be reduced 

 to formaldehyde in presence of metallic magnesium. This 

 experiment is of interest in view of the fact that, according to 

 WiUstatter, magnesium is an essential constituent of chloro- 

 phyll, just as iron is an essential constituent of the hsemoglobin 

 of the blood. It may be that we have here the first chemical 

 step in the series leading up to starch. 



The conversion of COg into formaldehyde and oxygen would 

 thus appear to be a purely chemical phenomenon, which under 

 the conditions of the laboratory quickly reaches a limit, but 

 which under the influence of biotic energy becomes continuous, 

 owing to the products of the reaction being quickly removed. 



This important first stage in plant assimilation may be 

 expressed by the following equations : — 



peroxide hyde 



The question still remains, presuming that the above 

 equations bear a close relation to actual fact, what is the next 

 stage between the simple carbohydrate, formaldehyde (CHjO), 

 and the more complex sugars and starches ? 



