ANTHOCYANINS AND GENETICS 209 



It is probable that the converse represents the synthesis in the 

 plant ; phloroglucin and the oxybenzoic acids and their derivatives are 

 widely distributed, and it is from these, no doubt, that the flavones are 

 synthesised. Hence the kind of oxybenzoic acid present affects the 

 kind of navone formed. Thus the ivory variety might be supposed 

 to form only one type of oxybenzoic acid, whereas the yellow forms two. 

 As yellow arises from ivory by the loss of a factor, we must look upon 

 this factor as the power of inhibiting the formation of luteolin, or the 

 oxybenzoic acid from which it is synthesised. This result is interesting 

 as a demonstration of the suggestion made by Bateson in the Presidential 

 Address to the British Association in 1914. He says : " I feel no reason- 

 able doubt that though we may have to forgo a claim to variations by 

 .addition of factors, yet variation both by loss of factors and by fractiona- 

 tion of factors is a genuine phenomenon of contemporary nature. If 

 then we have to dispense, as seems likely, with any addition from 

 without we must begin seriously to consider whether the course of 

 Evolution can at all reasonably be represented as an unpacking of an 

 original complex which contained within itself the whole range of 

 diversity which living things present." 



As regards the true white variety 1 , it lacks either the constituents, 

 one of them, or both, which go to make up the flavone, or the power 

 of synthesising the constituents. Many interesting lines for investi- 

 gation are suggested by these points, both in Antirrhinum and in 

 allied cases. The true whites might be tested for phloroglucin and 

 oxybenzoic acids, and the chemical composition of white individuals 

 bearing the I factor might be compared with those which are derived 

 from yellow, and which therefore do not carry I 2 . One point which 

 may be emphasised with regard to the Y and I factors is that their 

 power is not affected in the heterozygote ; a plant may be homo- or 

 heterozygous for Y or I, and there is no apparent difference in its colour. 

 This is not always so for factors concerned in anthocyanin formation, 

 as we shall see later; nor is it universal even for factors controlling 

 the formation of yellow pigment, as for instance in Mirabilis. In the 



1 A similar case to Antirrhinum is that of Phlox Drummondii, in which there is an 

 ivory white and a true white, the latter giving no canary yellow colour with ammonia. 

 I am indebted to Miss Killby for this information. 



2 I have noted that extracted solutions of white flowers almost invariably give brown 

 products, after standing, similar to Palladin's respiration pigments. This is rarely so 

 with extracts of ivory and yellow. The phenomenon suggests that aromatic substances 

 are present in the white which are not developed in the yellow and ivoiy. But further 

 and more careful investigation is necessary. 



w. P. 14 



