vn] THE FORMATION OF ANTHOCYANINS 119 



oxidase. Hence Keeble & Armstrong hold the view that in those 

 cases where albinos give the oxidase reaction, albinism is due to lack of 

 chromogen, but in the case of Geranium sanguineum, Dianthus and 

 flaked Primula, lack of oxidase causes lack of pigmentation. 



The assumption that albinism in Primula, Lathyrus and Pisum is 

 due to loss of chromogen must thus remain for the present until we have 

 further experimental data either for or against it. In the author's 

 experience the only instances of absence of chromogen (as determined 

 by the flavone reaction) are the albinos of Antirrhinum and Phlox 

 Drummondii. Flavones can be detected by the intense colour given with 

 alkalies, and this reaction was given by all albinos of Lathyrus and 

 Pisum examined. Nevertheless it must be admitted that this is no 

 direct proof, since there may be several flavones from only one of which 

 anthocyanin is derived. Keeble & Armstrong's views cannot however 

 explain the case of Antirrhinum, for we must suppose the ivory variety 

 to be an albino through lack of enzyme, since it contains the chromogen 

 (apigenin). Yet all ivory individuals tested by the author have con- 

 tained peroxidase. A possible explanation for this universal presence 

 of enzyme in ivories is that several oxidases are involved in pigment 

 formation. Thus only individuals free from all factors (and these are 

 extremely rare, as for instance 1 in 1024 when five factors are concerned) 

 would show no enzyme action. Yet at present there is no evidence 

 that more than one enzyme is involved. Another possibility is that in 

 Antirrhinum some third factor of a different nature is essential, con- 

 ceivably for condensation (see pp. 71, 211, 212). 



Consequently, as methods for detection of enzymes and chromogens, 

 one qualitative reaction is of no more value than another. Tissues 

 may give the flavone reaction, and yet we cannot be sure that the actual 

 chromogen of anthocyanin is present. Similarly, we have no absolute 

 proof from qualitative reactions for peroxidase that we are dealing 

 with a factor for colour. We may be localising areas where any 

 oxidative process is carried on (anthocyanin formation among others, 

 if it is oxidative). Apart, then, from the case of Antirrhinum of which 

 the chromogen has been isolated, and there is good evidence that only 

 one exists, little can be gained from speculations as to the presence or 

 absence of chromogens and oxidising enzymes, without more definite 

 isolation and analysis. Atkins (233, 246, 258), too, working with Iris 

 flowers has found that there is no satisfactory evidence for the co- 

 incidence of anthocyanin formation with the presence of oxidases. 

 Keeble, Armstrong & Jones (239) have also maintained that the 



