Mendelian Factors for Flower-Colour. 



301 



enzymes. Since some of the pigments involved (red, magenta) belong to the 

 group of so-called anthocyanins, i.e. soluble red, purple and blue pigments of 

 plants, general investigations were at first made by one of us* on anthocyanin 

 pigments. As a result of qualitative reactions, in conjunction with evidence 

 from cross-breeding, it was suggested that anthocyanins, as a group, are 

 oxidised products of the natural yellow colouring matters, the flavones and 

 xanthones. At the same time it was pointed out that a number of the latter 

 substances had been isolated by Perkin and othersf from various plants and 

 several had been shown to be widely distributed. The existence of many 

 flavones and flavone derivatives was mentioned and attention was drawn to 

 the fact that, as a group, they have similar properties but differ among 

 themselves in the number and position of their hydroxyl groups and in other 

 points. It was further suggested that the oxidised products (anthocyanins) 

 might, in a similar way, form a group of closely related substances, differing 

 individually according to the flavone from which each had been derived. 



In view of evidence collected from various sources, it was again suggested 

 by one of us,J that since the flavones are known to be present in many cases 

 as glucosides in the plant, the reactions involved in the formation of 

 anthocyanin might be stated in very general terms as follows : — 



Glucoside + water t^z flavone + sugar, 



x (flavone) + oxygen — * anthocyanin, 



and also that, in addition to oxidation, there might be condensation of the 

 flavone molecules. It was likewise stated that the first reaction might be 

 controlled by a glucoside-splitting enzyme and the second, if due to 

 oxidation, by an oxydase. 



Subsequent work has strengthened the view that anthocyanins are, in all 

 probability, derivatives of the flavones, though we ourselves have no further 

 evidence as to the actual nature of the reactions involved in their formation. 



Since we find little reliance can be placed on results given by crude water 

 or alcoholic extracts from flowers, in all later investigation's an attempt has 

 been made to deal with the isolated and purified pigments. In a paper by 

 one of us,§ the methods of preparation and purification of the crude pigment 



* Wheldale, M., "The Colours and Pigments of Flowers with special Eeference to 

 Genetics," 'Eoy. Soc. Proc.,' 1909, B, vol. 81, p. 44 ; " On the Nature of Anthocyanin," 

 ' Phil. Soc. Proc.,' Cambridge, 1909, vol. 15, p. 137. 



t Perkin, A. G., various papers in 1 Chem. Soc. Trans ,' from 1895 to 1904. 



% "Wheldale, M., "On the Formation of Anthocyanin," 'Journ. Genetics,' 1911, vol. 1, 

 p. 131. 



§ Wheldale, M., " The Flower Pigments of Antirrhinum majus. I. — Method of Prepara- 

 tion," 'Biochern. Journ.,' 1913, vol. 7, p. 87. 



