581.17 IS'i 



[March 



The Red and Blue Colouring Matters of Flowers 



I 



T is rather difficult to refer to an exact date the sober beginnings 

 of our present knowledge regarding the chromogens or the visible 

 colouring matters of flowers and leaves. Schubler and Decandolle 

 endeavoured to prove the existence of two essentially different series 

 of flower colours, viz., the xanthic producing the yellow tints with 

 their transitions into red, and the cyanic producing the blue tints 

 with their modifications, and that the colours of both series are 

 formed from chlorophyll, the xanthic by oxidation and the cyanic 

 by deoxidation. This view may, however, be considered as the result 

 of mere conjectural surmise rather than that of a definite chemical 

 investigation. The researches of Filhol, Cloez, and Fremy served 

 to elicit the distinction between the blue and red pigments which are 

 soluble in water, and many of the yellow which are of a resinous 

 nature and dissolve only in alcohol' and ether. The blue pigment 

 (cyanin or anthocyan) with acids makes red flowers, alkalies turn it 

 green ; and hence it was concluded that the blue colours of flowera 

 are not produced from the red by the action of alkalies. Tliey found 

 that blue, violet, red, brown, and orange flowers have only one- 

 colouring matter, while yellow flowers have two, viz., xanthin 

 insoluble in water, and xanthein soluble in water. According to- 

 Cloez and Fremy all red and rose flowers have an acid cell sap, and 

 the colour of this sap would be due to a modification, under the- 

 influence of an acid, of a colouring matter (cyanin), which is found 

 likewise, but in the state of greater purity, in blue flowers whose 

 sap is neutral. Finally, it was recognised by Filhol that the flowers- 

 of poppy. Pelargonium, Camellia, and Salvia contain a pigment 

 which is more stable than that of most other flowers, that they con- 

 tain no resin or xanthogen, and that when treated with alkalies they 

 assume a blue or violet colour without any green. Such were some 

 of the earliest researches on this intricate and most interesting 

 subject, and the fundamental error or defect which characterised 

 them all was that the rose, blue, and violet flowers owe their tints to 

 one and the same substance, influenced by the reactions of the vege- 

 table juices, this substance (cyanin) itself being a blue uncrystallis- 

 able mass soluble in water and alcohol, but insoluble in ether. 



This mistake is one which, in the absence of any definite know- 

 ledge anent the diflerences in kind and the sources of the various, 

 tannic chromogens, might have been easily made by anyone who- 



