352 PIGMENTS 



this view was provided by experiments which indicated that 

 for the production of anthocyanin, two factors are requisite — 

 the fiavonol, and an oxidizing enzyme. Thus a magenta 

 Antirrhinum produced two sports, an " ivory white," which 

 contained the fiavonol apigenin, a peroxidase, but no oxidase, 

 and a " dead white " which contained no fiavonol but pre- 

 sumably some other factor essential to anthocyanin formation, 

 since on crossing these two varieties, magenta fiowers resulted. 



Keeble and Armstrong * suggested that anthocyanin for- 

 mation is associated with the action of peroxidase upon a 

 chromogen ; they found that in coloured and recessive white 

 fiowers of Primula sinensis, the distribution of peroxidase 

 was identical with that of the pigment, whilst dominant white 

 varieties contain no peroxidase. This view has not found 

 acceptance ; in fact the mass of evidence leads to the conclusion 

 that neither peroxidase nor oxidase play a part in the fiavone- 

 anthocyanin system. f 



Views diametrically opposed to the idea that anthocyanin 

 is an oxidation product have been put forward by Combes J 

 who claims to have shown that Ampelopsis hederacea contains 

 both a fiavone and an anthocyanin and to have converted the 

 former into the latter by reduction and anthocyanin into 

 fiavone by oxidation. These views are criticized by Jonesco § 

 who considers the red pigments obtained by Combes were 

 due to the action of the acid used. 



Everest and Hall || examined a number of flower buds 

 selected for the well-marked anthocyan content of their mature 

 petals, such as auricula, apple, azalea, polyanthus, viola, etc. 

 In all cases it was found that before anthocyanin appeared 

 the petals were yellow or colourless, but they contained sub- 

 stances, presumably fiavonols, which turned yellow with am- 

 monia. On treating an alcoholic extract of a red rose and of 

 a mauve violet, collected before anthocyanin had appeared, 



* Keeble and Armstrong : " Proc. Roy. Soc," B., 1912, 85, 214. 

 t See Wheldale-Onslow : " The Anthocyanin Pigments of Plants," 

 Cambridge, 1925. 



+ Combes : " Compt. rend.," 1913, 157, 1002, 1454 J iQM. '58» 272. 



§ Jonesco : id., 1921, 173, 850, 1006. 



II Everest and Hall : " Proc. Roy. Soc," B., 1921. 92. 150- 



