ANTHOCYANINS 349 



o 



/\ 



CH CH 



II II 

 CH CH 



\/ 

 CH3 



which is a constituent of the anthocyanin structure, is also 

 the basis of the normal sugars having the amylene oxide 

 configuration- — 



CHOH . (CHOH)3 . CH . CU^OH, 



I I 



I 



O 



which may also be represented as follows — 



O 



CHOH CH . CHjOH 

 CHOH CHOH 



CHOH 



THE COLOUR OF PETALS. 



The pigments contributing to the colour of petals may 

 belong to any or all of the three groups, carotinoids, antho- 

 xanthins, and anthocyanins. 



In the case of white flowers, only anthoxanthins occur, and 

 these may be detected by the yellow colour developed on 

 exposure to ammonia. 



Yellow flowers, such as daffodils, contain both carotinoids 

 and anthoxanthins ; this may be shown by boihng the yellow 

 petals with alcohol, filtering and evaporating the filtrate to 

 dryness over a water bath ; the residue taken up with ether 

 and water on shaking in a separating funnel gives an ethereal 

 layer containing the carotinoids and an aqueous layer con- 

 taining the anthoxanthins. 



Brown flowers, such as wallflowers, contain anthocyanin in 

 addition to carotinoids and anthoxanthin ; to separate proceed 

 as for yellow petals ; the aqueous layer, which this time will 

 be brown, contains the two types of water-soluble sap pig- 

 ments ; if sufhciently concentrated, the flavonol glucoside, 



