MAQUENNE'S HYPOTHESIS 67 



from formic acid a sugar-like substance is formed, in con- 

 ditions such as obtain in an active leaf, which the plant 

 can utilize as a foodstuff. He points out that in Grafe's and 

 Baker's work the plants were in reality supplied with formic 

 acid, since formaldehyde is oxidized in the light, and he him- 

 self found that plants increased in dry weight in an atmosphere 

 of formic acid. Wislicenus * also supports the formic acid 

 hypothesis. The thesis, however, has attracted but little 

 attention, for which reason there is not enough evidence to 

 warrant a conclusion. 



MAQUENNE'S HYPOTHESIS. 



Maquenne f has formulated a theory of photosynthesis 

 which is independent of the formation of formaldehyde or 

 formic acid as intermediate products. 



According to current ideas, the conversion of n molecules 

 of carbon dioxide into a compound containing n carbon atoms 

 involves a polymerization which, according to the formalde- 

 hyde hypothesis, is subsequent to the formation of the inter- 

 mediate compound, formaldehyde. On Maquenne's hypothe- 

 sis, polymerization may precede or merely accompany the 

 decomposition of carbon dioxide. 



Willstatter and Stoll consider that chlorophyll may exist 

 in a true or in a colloidal solution ; J in the former state it is 

 unaffected by carbon dioxide but in the latter state carbon 

 dioxide and chlorophyll combine to form a compound of a 

 bicarbonate type. 



Maquenne suggests that colloidal chlorophyll is either a 

 simple hydrate of ordinary molecular chlorophyll or a polymer 

 in which the molecules are united by loose supplementary 

 valencies due, say, to the magnesium becoming tetravalent 

 as in formula III. 



On the addition of carbon dioxide and water, a substance 

 of formula I. results which by photochemical action yields 

 a compound of formula II. which, being unstable, gives off 



* Wislicenus : " Ber. deut. chem. Ges.," 191S, 51, 942. 

 f Cf. Maquenne : " Compt. rend.," 1923. >77». s 53- 

 1 See Vol. I., p. 307. 



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