290 SOME RECENT RESEARCHES IN PLANT PHYSIOLOGY 



Now, since direct chemical evidence shows that in some 

 cases, at least, a flavone when reduced gives an antho- 

 cyanidin, and this unites with a sugar to yield an antho- 

 cyanin, it appears that the peroxidase-system can have 

 nothing to do with the origin of the pigment. Such a view 

 cannot, however, be accepted without careful consideration, 

 for the relation between the absence of anthocyanin 

 and the presence of an inhibitor of oxidase action is very 

 striking. The anthocyanin of Antirrhinum, also, is too 

 complex a body to be accounted for by simple reduction. 



The third series of researches, those upon the abundance 

 of sugar in cells which form anthocyanin, seems, however, 

 to indicate what appears to the writer to be an explanation 

 of the conflicting evidence. Palladin has pointed out that 

 tissues richly supplied with sugar become richer both in 

 oxidizing enzyme and in chromogen. Thus, since antho- 

 cyanins have been shown to arise in tissues with a similar 

 abundance of sugars, it may well be that the coexistence 

 of oxidase and of anthocyanin in the same cell is due 

 to the fact that abundance of sugar favours the forma- 

 tion of both, and need not involve the production of the 

 pigment by the enzyme-system. Indeed, if the latter 

 is concerned in the respiration of sugars, the production 

 of the enzyme in quantity when its substrate is present 

 in large amount is quite in keeping with the behaviour 

 of cells with regard to other enzymes, and offers a sufficient 

 explanation of the function of the oxidase. Such a view, 

 however, leaves out of account the known facts with regard 

 to the distribution of anthocyanin and inhibitor. 



The following suggestion is here offered in a tentative 

 manner as an endeavour to correlate the evidence fur- 

 nished by the t two lines of research. Palladin (1908, 1, 2) 

 in his earlier papers conceived of plant respiration as a 

 taking Jn of oxygen by a readily oxidizable substance, 



