156 LIGHT, VEGETATION AND CHLOROPHYLL 



Boussingault and Bayer expressed the view that glucosides 

 resulted from the union of carbon with the elements of water, 

 hence their first name of carbohydrates. Most of the formulae 

 representing glucosides can, in fact, be written as if they 

 were the result of the polymerization of this fundamental 

 molecule CHgO, for example, glucose, CgHiaOg or (CH20)6. 



It was not difficult to find tliis molecule from which all 

 the glucosides would be derived since the carbon dioxide had 

 only to replace its 2 atoms of oxygen with a molecule of 

 water according to the equation 



CO2+H2O— ^CH^O+Oa 



Such a reaction, simple as it may be on paper, immediately 

 seemed to be improbable, and a double decomposition of 

 carbon dioxide and water was suggested, showing carbon 

 monoxide combining with hydrogen: 



CO2 — >co+o 



H2O— ^H2+0 

 CO+H2 ^CHaO 



If this were so, photosynthesis ought to be facilitated when 

 carbon monoxide is given to the plant, but this gas is quite 

 unsuitable for the purpose. 



Another suggestion was that carbonic acid, which is 

 normally formed by the contact of carbon dioxide and water, 

 might have some part in the reaction; it would need only to 

 lose 2 atoms of oxygen 



CO3H2 ^CH20+02 



Nobody succeeded in explaining how such a reduction 

 could be accompUshed in the plant, but, since photosynthesis 

 certainly existed, it had to be admitted that the reduction did 

 actually take place. 



The first result then of photosynthesis is formaldehyde, 

 HCHO. From this Fischer was able to effect the synthesis of 

 glucosides, which contributed in no small measure to the 

 success of the theory. 



Nevertheless, formaldehyde is a poisonous substance to the 

 plant, even in small quantities, and its presence in the plant 



