viz] THE FORMATION OF ANTHOCYANINS 125 



From 33 gnis. of quercetin, 0-165 gm. of the product was obtained. 

 It seems to be open to criticism to assume that this product is formed 

 by reduction ; it is also doubtful whether the analysis (by combustion) 

 forms an efficient proof of its identity with cyanidin, though its resem- 

 blance in chemical and physical properties certainly lends support to 

 the statement. Granted, however, that cyanidin is formed from quer- 

 cetin by reduction, we still have no proof that this is the process employed 

 by the living plant. 



The contents of the present chapter may be summarised as follows. 

 There is strong evidence for the belief that anthocyanins are formed from 

 the flavones, and that these substances are the chromogens of the 

 Mendelian writers. But the actual processes involved are still debatable. 

 There is evidence, from Keeble & Armstrong's work, that the presence 

 of anthocyanin is often connected with the presence of oxidases, but there 

 is no proof that oxidases are the agents in transforming flavones into 

 anthocyanins. From the analyses of pigments of Antirrhinum, it appears 

 that the anthocyanins of that genus are more oxidised than the flavone, 

 apigenin, which is present in the plant, and the artificial product 

 formed by reduction from apigenin is moreover not identical with a 

 natural anthocyanin. On the other hand, there is the evidence from 

 Willstatter's experiments that quercetin on reduction will produce, as 

 a by-product, a substance identical with a natural anthocyanin. To 

 obtain a satisfactory solution to the problem, further experimental 

 work is necessary, especially on the lines of isolation and analysis of 

 other plant anthocyanins and the flavones which accompany them 1 . 



1 See also Appendix. 



