1 64 THE CARBOHYDRATES 



tricity through a solution of carbon dioxide in water. Fenton * 

 also has pointed out that the synthetic action of light and of 

 the silent electrical discharge are practically identical. Thus 

 there is evidence which suggests that electric energy may play 

 a part in the earlier processes of photosynthesis ; a suggestion 

 which is supported by the fact that, according to Polacci,f the 

 formation of carbohydrates is promoted in leaves by electrical 

 energy, provided it be not too intense, especially when a con- 

 tinuous current is made to pass directly into the tissues. 



As a result of a number of experiments, Gibson t comes to 

 the conclusion that the light rays which are absorbed by the 

 chlorophyll are transformed into electrical energy, and it is 

 this transformed energy which brings about the decomposition 

 of carbonic acid to formaldehyde and oxygen. 



With regard to other forms of energy, the results obtained 

 by Usher and Priestly with radium emanations and with ultra 

 violet rays have been mentioned. Attention may be drawn 

 also to the work of Kernbaum, who found that water exposed 

 to the influence of /3 rays and of ultra-violet rays led to the 

 production of hydrogen and hydrogen peroxide. Also Berthe- 

 lot and Gaudechon II found that formaldehyde is produced by 

 the action of ultra-violet rays on carbon dioxide in the presence 

 of a reducing agent 



The question now arises as to how the sugars are produced 

 from the formaldehyde, presuming the latter to be formed. 

 Living leaves contain many different sugars ; thus Meyer, in 

 1885, found that cane sugar, maltose, dextrose and levulose all 

 were present. Later, Brown and Morris IF described that, in 

 the case of the leaves of Tropaolum, cane sugar accumulated 

 while the hexoses remained practically constant in amount. 

 Meyer also states that the di- and polysaccharides increase 

 while the photosynthetic processes are active, while, in the dark, 

 the monosaccharides increase. 



If Baeyer's hypothesis be correct, then it would naturally 



* Fenton : " J. Chem. Soc., Lond.," 1907, 91, 687. 



t Polacci: " Atti. Inst. Bot., Pavia," 1905, II, n, 7. 



% Gibson : " Ann. Bot.," 1908, 22, 117. 



Kernbaum : " Compt. rend.," 1909, 148, 705 ; 1909, 149, 273. 



II Berthelot and Gaudechon : id., 1910, 150, 1690. 



IT Brown and Morris: " J. Chem. Soc., Lond.," 1893, 63, 604. 



