anthocyan-iron salt is present in these flowers. Tbe"^ -tu gy Sm^f^ e/ffst 



Anthocyanins and AnthocyanidinsiA f^)( 2 3 



/ 



therefore be due to the presence of anthocyan phenolates of the alkali or 

 alkaline-earth metals. 



In the case of the flowers of the hydrangea, in which the pigment 

 assumes a blue colour after the addition of iron salts to the soil in which 

 the plant is grown, it is quite possible that we have an example of the other 

 type, and that the pigment is a complex anthocyan-iron salt. As the authors 

 have not yet been able to examine these flowers, a decision upon this point 

 must be left until later. 



The extended botanical investigations of Keeble, Armstrong and Jones,* 

 and of Wheldale.t indicated that a relationship existed between the yellow 

 sap-pigments and the anthocyans, whilst Everest has described work which 

 brought him to the conclusion that in Nature the anthocyan colouring 

 matters are produced from yellow sap pigments (of the flavonol group) by 

 reduction.^ 



The present authors now describe observations which appear to prove 

 that, at least in some cases, this conclusion is fully justified. The experi- 

 ments now described were undertaken with a view to extending our insight 

 into the mechanism of production of the anthocyan pigments in Nature. 



Although it has already been established by the work of Willstatter and of 

 Everest, that the anthocyan pigments may be produced by reduction of 

 flavonol derivatives, it has not previously been so clearly indicated whether,, 

 in Nature, flavonols are first formed and from them the anthocyans, or the 

 anthocyans directly synthesised and the flavonols produced from them by 

 oxidation. 



Additional interest was given to the matter by a lecture by Dr. E. Eobinson, 

 F.E.S. (then Professor of Chemistry in the University of Liverpool), at the 

 University of Manchester, in which he dealt with the theoretically possible 

 synthesis of plant products from sugars. He indicated the manner in which 

 the synthesis of anthocyans from sugars might take place in Nature, and also 

 pointed out that it was less easy to indicate how flavonols could be synthesised 

 from sugars. As a result of these theoretical considerations. Dr. Eobinson 

 contended that the flavonols were formed from anthocyans by oxidation, the 

 anthocyans being the primary synthetic products. 



* 'Eoy. Soe. Proc.,' B, vol. 85, p. 214 (1912) ; vol. 86, pp. 308 and 318 (1913) ; vol. 87, 

 p. 113 (1913) ; and Keeble and Armstrong, 'Jour. Genetics,' vol. 2, p. 277 (1913). 



t *Camb. Phil. Soc. Proc.,' vol. 15, p. 137 (1909) ; 'Jour. Genetics,' vol. 1, p. 133(1911) ; 

 'Biocliem. Jour.,' vol. 7, p. 87 (1913). 



t ' Eoy. Soe. Proc.,' B, vol. 87, p. 444 ; vol. 88, p. 326 ; and vol. 90, p. 251. 



The Mode of Formation of Anthocyan Pigments in Plants. 



