CHAPTER IV 



THE PROPERTIES AND REACTIONS OF ANTHOCYANINS 



From time to time the question has been under discussion as to 

 whether all the varieties of red, purple and blue plant pigments- are 

 merely one and the same compound, the different shades being due 

 to the presence of other substances in the cell-sap, i.e. acids, alkalies, 

 etc., or whether the term anthocyanin includes many different members 

 of a great group. The earliest expression of opinion on this point is 

 possibly that made by James Smithson (112) in the Proceedings of the 

 Royal Society in 1818; here he remarks, on the slightest experimental 

 basis: "The colouring matter of the violet exists in the petals of red 

 clover, the red tips of those of the common daisy of the fields, of the 

 blue hyacinth, the holly hock, lavender, in the inner leaves of the 

 artichoke, and in numerous other flowers. It likewise, made red by 

 an acid, colours the skin of several plumbs, and, I think, of the scarlet 

 geranium, and of the pomegranate tree. The red cabbage, and the 

 rind of the long radish are also coloured by this principle. It is remark- 

 able that these, on being merely bruised, become blue; and give a 

 blue infusion with water. It is probable that the reddening acid in 

 these cases is the carbonic; and which, on the rupture of the vessels 

 which enclose it, escapes into the atmosphere." In the same way 

 Marquart (5), and Fremy & Cloez (126) originally recognised only 

 one blue pigment, from which the red pigments were believed to be 

 derived by action of acids. Of a similar opinion was Wigand (136), 

 who writes : " Die rothe und blaue Farbe der Bliithen sind, wie sich theils 

 aus den Uebergangserscheinungen, theils aus dem Auftreten beider 

 Farben als homogene Farbimg der Zellenfllissigkeit, theils aua dem 

 iibereinstimmenden Verhalten beider gegen chemische Reagentien 

 ergiebt, unwesentlich verschiedene Zustande eines und desselben Stoffes, 

 des Antliocyans." Hansen (11), also, believed most red flower colours 

 to be due to one substance. 



