The Production of Anthocyanins and Anthocyanidins. 255 



varieties of the same species, will be fully realised when the work of 

 Willstatter and his collaborators on the anthocyan pigments, in particular 

 WilLstatter and Mallison,* or that of A. Gr. Perkin, on the various cotton 

 flowers,-]- is considered. 



One further case needs consideration : CombesJ states that he has 

 isolated a crystalline anthocyan pigment from the red autumn leaves of 

 Ampelopsis hederacea, whilst from green summer leaves of the same plant he 

 obtained a yellow-brown sap-pigment in crystalline condition. He further 

 states that, by reduction of the yellow compound, he obtained a substance 

 (crystalline) that was identical with the anthocyan, and vice versa ; by oxida- 

 tion of the anthocyan he obtained the yellow-brown compound in crystalline 

 form, and identical with that obtained from the green leaves. In this case 

 neither anthocyan nor yellow colouring matter has been identified, whilst 

 the published data, which are scanty, leave the impression that his anthocyan 

 may consist of crystals of a flavone derivative coloured red. 



The Colouring Matters of the Viola. 



At the time when the present work was commenced, our knowledge of the 

 colouring matters of the Viola species was confined to the yellow pigments. 

 Viola-quercitrin, from Viola tricolor, had been isolated and investigated by 

 various workers, and finally proved to be quercetinrhamno-glucoside,§ whilst 

 A. Gr. Perkinll had shown that in the ordinary Violet ( Viola odorata) there 

 is also present a glucoside of quercetin. It is interesting to note that the 

 latter investigation was carried out with the ordinary violet-coloured 

 flowers, not with white Violets (this was not specifically stated in the 

 paper cited, but has been intimated to the author by Prof. Perkin).ir 



The author proposes to examine systematically the different species of 

 Viola, with a view to isolation and identification of both the yellow flavone, 

 also the anthocyan pigments present in them. At the outset, self-coloured 

 varieties were chosen, and, feeling that the anthocyan would probably 

 give more trouble in isolation than the yellow pigment, one that contained 

 a very large percentage of anthocyan pigment — Sutton's " Black Knight " 

 — was first taken for investigation. 



The plants from which the flowers were gathered were mostly grown for 



* ' Annalen,' vol. 408, p. 147 (1915). 



t ' Joui n. Chem. Soc.,' 1916, p. 145. 



X ' Compt. Eend.,' vol. 157, p. 1002 ; vol. 157, p. 1454. 



§ A. G. Perkin, ' Journ. Chem. Soc.,' 1910, p. 1776. 



II ' Journ. Chem. Soc.,' 1904, p. 58. 



IT The author proposes to isolate and identify the anthocyan pigment from the Violet, 

 und thus complete the data. 



