60 THE SYNTHESIS OF CARBOHYDRATES 



to the vapour of formaldehyde, and Sabalitschka and Weidling * 

 observed that Elodea is able to build carbohydrate from solu- 

 tions containing 0-024 P er cent, of formaldehyde or 0-032 per 

 cent, of acetic aldehyde in darkness as well as in light. 



There is much positive evidence of the presence of formal- 

 dehyde in green leaves. Thus Klein and Werner f from their 

 experiments conclude that formaldehyde and acetic aldehyde 

 thus occur ; the former was only found in leaves in which 

 carbon assimilation had taken place ; it was absent in leaves 

 kept in an atmosphere free from carbon dioxide, or grown in 

 darkness, and in leaves narcotized by phenyl urethane or by 

 hydrocyanic acid. Acetic aldehyde, on the other hand, was 

 found in narcotized leaves, and also in leaves kept in darkness ; 

 it is regarded by the authors as a product of respiration. 



Mention has above been made of the formation of formal- 

 dehyde and of formic acid from carbon dioxide and water 

 under the influence of different forms of energy. 



Willstatter and Stoll % argue that the " assimilatory ratio," 

 C0 2 /0 2 , should provide evidence regarding the possible inter- 

 mediate products ; they point out that oxalic, formic and 

 glyoxylic acids and formaldehyde are possible intermediate 

 products between the carbon dioxide and carbohydrate. The 

 assimilatory ratios of these substances are respectively, 4, 2, 

 1-33 and 1. In their experiments, they found the assimilatory 

 ratio to be 1 and it remained constant, even in succulents, in 

 varying amounts of carbon dioxide and oxygen and with the 

 temperature ranging from io° C. to 35 C ; it is concluded 

 therefore that the carbon dioxide is reduced to formaldehyde, 

 this being the only product having a single carbon atom. 



POLYMERIZATION OF FORMALDEHYDE TO SUGARS 



IN VITRO. 



Laboratory experiments on the polymerization of formal- 

 dehyde to sugars not infrequently are quoted in support of 

 the formaldehyde hypothesis. 



t Sabalitschka : " Z. angew. Chem.," 1922, 35, 684. Sabalitschka 

 and Weidling : " Biochem. Zeit.," 1926, 172, 45. 



* Klein and Werner : " Biochem. Zeit.," 1926, 168, 361. See also 

 Vol. I., Section on Aldehydes. 



I Willstatter and Stoll: " Ber. deut. chem. Gesells.," 1917, 50, 1777. 



