460 M. Wheldale. 



Broadly speaking, I believe anthocyanin formation to be analogous 

 to the particular oxidative processes, so strikingly illustrated by the 

 activities of laccase and tyrosinase. Nevertheless one important 

 difference must be borne in mind, namely, that whereas lacquer, and 

 the brown or black bodies formed on injury, are the after products 

 of disintegration and death, anthocj^anin is the pigment developed 

 by the living plant. 



I have elsewhere^) given evidence for my belief that except in 

 certain cases ^j plant cells in general contain soluble aromatic sub- 

 stances of the nature of flavones; unquestionably anthocyanin is also 

 very widely distributed: further, and to this point I shall return 

 later, it is highly probable that all living tissues of anthocyanic 

 plants have the power to form oxydases. Hence the deduction, upon 

 which I wish to lay emphasis, is, that certain oxydases may act as 

 oxygen-carriers transferring oxygen to the flavones and thereby 

 oxidising them to coloured products — anthocyanin. The latter may 

 be again transformed into chromogens by the reducing action of 

 other bodies in need of oxygen. If such be the case, every cell is 

 provided with the mechanism for anthocyanin formation; it is not 

 however this mechanism alone which controls the production of pig- 

 ment but the sum total of the metabolic activities of the tissues. 



In short, anthocyanin may be regarded as the by-product of 

 oxidative metabolism. Should the local oxidising capacity of any 

 tissue be greater than its reducing power, this is indicated by the 

 local appearance of anthocyanin; if the reducing be greater than the 

 oxidising power, no pigment results. The evidence, upon which the 

 validitj^ of the above statement rests, will now be discussed in some 

 detail. 



The Theory of Chodat and Bach. 



Until the appearance of the work of Chodat and Bach^), no 

 very clear conception had been formulated as to the nature and 

 mode of action of oxydases. The publications of these authors have 

 done much to explain the misconceptions of earlier workers and 



') Proc. Cam. Phil. Soc, Vol. 15. 1909. 



^) In Antirrhinum majus and Phlox Drummondii an albino variety arises 

 through loss of power to form the chromogen. Cf. Wheldale. Proc. Roy. Soc. B., 

 Vol.81. 1909. 



■*) Variolas papers in the Ber. d. d. chem. Ges. 1903 and following years. 



