182 



Prof. B. Moore and Mr. T. A. Webster. 



this purpose have used salts of uranium. The reactions of de-duplication of 

 these organic substances in dilute solutions take place, however, quite readily 

 without a chemical catalyst. The reactions are exothermic, and the light 

 itself acts as the catalyst. 



This production of formaldehyde has several important and interesting 

 relationships which may now be pointed out. 



In the first place, it has a practical bearing on all enquiries as to the 

 presence of formaldehyde in green leaves exposed to light, or of chlorophyll 

 solutions, or artificial schemata of various types, exposed to light and after- 

 wards tested for formaldehyde to elucidate the functions of the chloroplast 

 in the green leaf. Many observers throughout the past generation have 

 laboured at proving the presence of formaldehyde in green leaves exposed to 

 light, but if it is so that practically any organic substance of bio-chemical 

 origin exposed to light develops formaldehyde, then the presence of form- 

 aldehyde in green leaves furnishes no proof of its synthesis by sunlight from 

 carbon dioxide and water. The same holds for all the schemata, for these 

 always contain substances from which formaldehyde could arise. But even 

 although no other organic substance save chlorophyll, or an}' mixture of pure 

 chlorophylls, were present and yet formaldehyde were formed in abundance 

 on exposure to light, this would be of no avail as a proof of photo-synthesis 

 of formaldehyde from the inorganic, for the same •change would happen in a 

 solution of cane sugar, and there is no proof that the chlorophyll is not 

 simply behaving like a legion of other organic compounds and yielding 

 formaldehyde by its own decomposition. 



It has recently been shown by Jorgensen and Kidd* that pure chloro- 

 phylls exposed as a suspensoid sol in water to light in presence of oxygen, 

 at first bleach, and then yield formaldehyde. When exposed in presence of 

 nitrogen only or a full atmosphere of carbon dioxide no formaldehyde was 

 produced. Under natural conditions in the leaf and under all conditions of 

 exposure to light of artificial schemata, used by previous observers, there has 

 always been present atmospheric oxygen, so that this appearance of form- 

 aldehyde from pure chlorophyll emulsions after exposure to light confirms 

 the view expressed here as the result of our experiments. 



In the second place, the general production of formaldehyde when these 

 substances resolve themselves under the influence of light into simpler forms 

 possesses a teleological bearing, for if in the uptake of solar energy the first 

 storage from the inorganic be in the stage of formaldehyde, it would be very 

 probable that in the process of unbuilding this step should be retraced. 



* ' Roy. Soc. Proc.,' B, vol. 89 p. 342 (1916). 



