186 A. J. Eiuart: 



mates and methyl alcoliol. The alkali is used up and the amount 

 of sugar formed is proportionate to the amount of alkali consumed. 

 The reaction is, therefore, widely different from an enzymatic one. 

 No mode of enzymatically polymerising formaldehyde to sugar is 

 known, such as might occur in plants. 



Conclusions. 



The foregoing research was undertaken in order to elucidate cer- 

 tain points of interest to the plant physiologist concerning the 

 possible modes in which plants could synthesize sugar from formal- 

 dehyde, which the purely chemical researches available did not 

 appear to answer. It has led me to the conclusion tliat a produc- 

 tion of formaldehyde does not form a stage in tlie synthesis of 

 «ugar by plants, and that it would be a very wasteful, indirect way 

 of producing sugar. 



The reasons on which this conclusion are based are as follow : — 



(1) In 1908 I showed that when chlorophyll was oxidised in the 

 presence of light, and in the absence of carbon-dioxide, one of its 

 decomposition products Avas formaldehyde, and that tliis was the 

 explanation of the appearance of traces of formaldehyde in green 

 leaves exposed to light. This result has been confirniel by Schryver 

 .and by Jorgensen and Kidd.* Schryver stated tliat more t'ormal- 

 idehyde was produced when carbon dioxide was present, but as the 

 results of experiments extending now over ten years, there can he 



-no doubt that the process is purely one of photo-chemical oxidation, 

 and is not increased by the presence of COo. 



(2) There are strong reasons for concluding that alkalies do not 

 polymerise formaldehyde to sugar, oi- only to a very .slight extent, 

 but inst?ad produce methyl alcohol an>\ formates. Pronounced su^ar 

 formation only takes place when the alkali acts on a polymer, such 

 as parafornuildehyde, the polyhydrate, or metaformaldeliyde. The 

 production of sugar from a solution of formaldehyde mainly 

 depends on the presence of the polyhydrate in tlie solution. With 

 cold dilute solutions the production of sugar is almost negligible. 

 For a complete reaction and higli polymerisation a temperature 

 of OCC. to lOO'^C. is necessary. Even then tlie polymerisation is 

 only partial, and formates and methyl alcohol are formed in large 

 .amount. These are not known to accompany photosynthesis in 

 plants. 



* Ewart, Proc. Royal Soc. Loud., B 1908, Vol. SO, p. 30; Schryver, ibid. 1910, 82, \\ 226; 

 Jorgcnson and Kidd, ibid. 1917, 89, p. 342. 



