ANTHOCYANINS AND GENETICS 211 



Bearing in mind then the reversible nature of many reactions in 

 the plant, we may suppose, assuming the factors to represent the power 

 to bring about plant reactions, two possibilities; when a factor is 

 lost, the reaction it represents may not take place at all ; or it may 

 take place, from lack of control, in the opposite direction from the 

 normal. 



Thus it would be possible to regard the ivory factor, I, as a reducing 

 agent, since luteolin is more highly oxidised than apigenin. When 

 the control of the reducing agent is removed from the epidermis, the 

 oxidising action can progress and luteolin is formed. The explanation, 

 however, may rest upon a more fundamental basis; the structure of 

 the living molecule in the ivory and yellow plants may be different, 

 so that one casts off, or synthesises, a different type of flavone or acid 

 from the other. 



We may next turn to the factors concerned with anthocyanin forma- 

 tion. There are three groups of factors to be considered: 



(a) Those concerned with the actual formation of pigment. 



(6) Those controlling the amount formed. 



(c) Those modifying the colour of the pigment after it is formed. 



From results obtained with Lathyrus and Matthiola, it appears that 

 two factors, which have been termed C and R, are necessary for the 

 process of anthocyanin formation. The question before us is what 

 reactions of the process do C and R control? It has been suggested 

 that they represent respectively a chromogen, C, and an oxidase or 

 oxidising enzyme, R. The recent work of Willstatter on anthocyanin, 

 coupled with the results from Antirrhinum, makes it practically certain 

 that the anthocyanins are derived from flavones. The flavones there- 

 fore are the chromogens of anthocyanin. In Antirrhinum it is clear 

 that the ivory variety carries the chromogen, C, and the white variety, 

 a factor R it is only necessary to postulate one in this case for 

 the production of anthocyanin. 



With regard to Lathyrus and Matthiola, in the absence of exact 

 chemical investigation, we can only make the following surmises. The 

 two whites which produce colour must differ in some respect; one may 

 contain the chromogen, C, the other the colour producer, R ; or both 

 may contain chromogen, and some other unknown factor in addition 

 to R may be involved in colour formation. We can deduce very little 

 from the facts observed. Both the whites (which when mated give 

 colour) contain a flavone or flavones, for both turn yellow with alkalies, 

 but this need not necessarily imply that both contain the chromogen, 



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