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Mr. H. Wager. 



oxidising agents. This led me to suspect that the yellow colouring matter 

 extracted from etiolated leaves — leaves in which only a yellow colouring- 

 matter had developed — would give the same results. The yellow-orange 

 colouring matter extracted from etiolated rhubarb leaves was found, 

 however, to bleach more slowly, both in light and in oxidising reagents, 

 than ordinary chlorophyll obtained from grass, and very much more slowly 

 than the yellow pigment from grass chlorophyll. Whether this has 

 anything to do with the lack of photo-synthetic activity which Miss Irving* 

 has found in chlorophyll not completely developed I cannot say, but, 

 considered in the light of Miss Irving's observations, that the photo-synthetic 

 activity of chlorophyll does not reach its full strength until the chlorophyll 

 has been fully formed, the retardation of the photo-oxidation of the etiolin is 

 ■of considerable interest. 



It is, of course, possible that the yellow colouring matters from other 

 plants may be found to behave differently in this respect, and too much 

 stress must not be laid, therefore, upon the experiments just described. It 

 is proposed to continue these observations. 



The Action of Reducing Agents upon Oxidised Chlorophyll. 



We have seen that the photo-oxidation of chlorophyll results in the pro- 

 duction of an oxidising substance and of an aldehyde. Both are therefore 

 oxidation products, and it was of some interest to ascertain the action of 

 reducing agents upon them. 



Three strips of paper coloured green by grass chlorophyll in a petroleum 

 ether solution were exposed to the light until visibly bleached : 1 and 2 

 were then placed in a strong solution of phenylhydrazine, 3 was cut in two 

 and one portion was treated with Schiffs solution, the other with a 10-per- 

 cent, solution of potassium iodide. Both gave a strong reaction. After being- 

 kept in the phenylhydrazine solution for three hours, 1 was placed in Schiffs 

 solution, 2 in potassium iodide solution, and in neither case was any reaction 

 obtained. 



Similar results were obtained with stannous chloride, and with a pyro-soda 

 photographic developer. 



Chlorophyll paper oxidised in the dark by the permanganate of potash 

 solution, then treated for three hours with phenylhydrazine hydrochloride also 

 gave no reaction either with Schiffs solution or potassium iodide. 



The reducing agents do not bring back the green colour to the oxidised film, 

 but the activity of both the products of chlorophyll photo-oxidation is 

 destroyed. ■ 



* 'Ann. Bot.,' 1910. 



