1913.] Formation of the Anthocyan Pigments of Plants. 315 



they fade a new colour, and we know that the colour of some flowers under- 

 goes a marked change during the course of the day. Such changes are to be 

 ascribed to the simultaneous presence in the petals of pigments, chromogens, 

 oxidizing and reducing agents. 



"We have now to consider the conditions under which recovery of colour 

 occurs. 



Evidence has been given already in favour of the interpretation that 

 recovery is brought about by the oxidation of chromogen. 



There is, however, one series of facts, namely, those bearing on recovery of 

 colour by petals immersed in strong alcohol, which seems to throw doubt upon 

 this conclusion. 



For, as several investigators have shown, increasing concentrations of 

 alcohol exercise a progressively adverse effect on enzyme action. Thus, 

 Hudson (1910),* working with inverta.se has expressed the effects of different 

 concentrations of alcohol in the form of a regular curve. He finds that in 

 70-per-cent. alcohol invertase retains only 10 per cent, of its activity. 



We have studied the relation of the activity of maltase to alcoholic con- 

 centration and find that this enzyme is even more sensitive to ethyl alcohol 

 than is invertase ; the activity of maltase ceasing in 60 per cent. With 

 methyl alcohol a 40-per-cent. solution suffices to render the enzyme inactive. 



Our experiments with emulsin, which confirm those published in 1912 by 

 Bourquelot, give results similar to the foregoing except in one important 

 particular. 



The activity of emulsin falls rapidly as the concentration of alcohol increases 

 to 40 per cent. After this point is reached the activity falls off more slowly 

 and some activity may be detected in solutions containing 90 per cent, of 

 alcohol ; in solutions containing from 40 to 90 per cent, of alcohol the activity 

 of emulsin is proportional roughly to the amount of water present in the 

 solution. 



For the purpose of investigating the effect of alcohol on oxydase we have 

 made use of the Lovibond tintometer. We measure by means of this 

 apparatus the depth of coloration — a mixture of red and yellow — produced by 

 the action of bran peroxydase on guaiacol. 



The curve representing the amount of oxydase action — as measured by the 

 tintometer — is similar to the curves which have been obtained for invertase, 

 maltase and emulsin. As the alcoholic strength increases the activity of 

 oxydase falls. In 50-per-cent. solutions it becomes very small and ceases 

 altogether in 70-per-cent. alcohol. Alcohol causes a similar retardation of 



* Hudson, C. S., ' U.S. Dept. of Agric, Bureau of Chemistry, Circular 58.' 



