PEOCEEDINGS OF 



THE EOYAL SOCIETY. 



Section B. — Biological Sciences. 



On the Function of Chlorophyll. 



By Alfred J. Ewart, D.Sc, Ph.D., Professor of Botany and Plant Physiology 

 in the Melbourne University and Government Botanist of Victoria. 



(Communicated by Prof. A. C. Seward, F.R.S. Received January 19, 1915.) 



It has been generally assumed that the function of chlorophyll is to absorb 

 radiant energy from light and to render this available for the production of 

 formaldehyde from carbon dioxide and water, the formaldehyde being 

 subsequently polymerised to carbohydrates, and oxygen being set free. This 

 is supported by the fact that chlorophyll contains magnesium* and that in a 

 cold watery solution of carbon dioxide this metal produces formaldehyde,t 

 which readily polymerises spontaneously to paraformaldehyde, C2H4O2, or 

 metaformaldehyde, C 3 H 6 03, and into hexose sugars in the presence of lime- 

 water or other weak alkali. 



Usher and Priestlyj stated that chlorophyll films when exposed to sunlight 

 decomposed carbon dioxide, producing formaldehyde and hydrogen peroxide. 

 The latter was responsible for the bleaching of chlorophyll in sunlight, and 

 if a " katalase " enzyme was present the oxygen was set free and the 

 chlorophyll remained green. " The bleaching of the chlorophyll in sunlight 

 whether carbon dioxide is present or not is due to the formation of hydrogen 

 peroxide." As a matter of fact chlorophyll films immersed in a solution of 

 hydrogen peroxide remain green for a long time in darkness, and when 



* A full account of the work on the chemistry of chlorophyll, by Willstatter and 

 others, is given in the ' Chemistry of Plant Products,' by Haas and Hill, pp. 222-241 

 (1913). 



+ Fenton, ' Journ. Chem. Soc.,' vol. 91, p. 687 (1907). 



% 'Eoy. Soc. Proc.,' B, vol. 77, p. 369 (1906); vol. 78, p. 318 (1906) ; vol. 84, p. 101 

 (1911). 



VOL. LXXX1X. — B. B 



