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Prof. Keeble, Dr. Armstrong, and Mr. Jones. [Feb. 3, 



stated already, a petal recovers its colour in water at room temperature in the 

 space of a quarter of an hour. At higher temperatures the recovery is more 

 rapid and if a petal be dropped into water which has been heated to near the 

 boiling point the recovery of colour is almost instantaneous. 



We turn now to the detailed interpretation of the facts of loss and 

 recovery of colour ; and we deal first with the loss of colour which takes 

 place when petals are dehydrated. 



The evidence about to be given supports the conclusion that the loss of 

 colour is clue to the action of a reducing agent. In the present state of ojir 

 knowledge of the reducing processes which occur in the cells of plants it is 

 not possible to affirm that the agents of these processes are of the nature of 

 specific catalysts. We propose therefore to avoid using the word reductase 

 and to employ the indifferent term " reducing agent " in the description of 

 the phenomena of decolorisation. 



A careful examination of the petals of stocks subjected to the action of 

 alcohol makes it difficult to escape from the conclusion that decolorisation is 

 due to the activity of a reducing agent. It is easy to demonstrate that the 

 loss of colour is not due merely to a dissolution of the pigment and its 

 diffusion throughout a large bulk of fluid. 



As evidence that the loss of colour is due to the action of a reducing agent 

 we may cite the following facts : — 



The immersion of the petals in alcohol produces three immediate effects, — 

 a rapid evolution of gas, a reduction in the amount of colour, and a discharge 

 from the petals of a certain amount of pigment which dissolving in the 

 alcohol gives rise to a marked coloration of that reagent. 



Similar effects are produced, but more rapidly, if previously to their 

 immersion in alcohol the petals are treated for about half a minute with 

 chloroform. 



As a consequence of the discharge of the pigment the alcohol becomes 

 deeply coloured— purple or red according to the variety of stock used in the 

 experiment. If the alcohol be decanted at once its colour disappears with 

 remarkable rapidity and in less than 5 minutes the liquid becomes 

 colourless or at most faintly coloured. The partly decolorised petals, from 

 which the first lot of alcohol was removed, if treated with more of this 

 reagent, undergo further decolorisation, but at a much slower rate. The 

 simultaneous evolution of gas and the discoloration suggest that the effect 

 of the alcohol is to liberate a reducing agent which brings about the 

 deoxidation of pigment and an evolution of oxygen. Further evidence of 

 the presence of such a reducing agent is provided by extracts prepared by 

 pounding fresh petals with alcohol. The colour of the extract is at first 



