6o COLOUR IN NATURE 



Pigments of Flowering Plants 



Among the flowering plants chlorophyll is of 

 course the supremely important pigment. With it 

 as already seen are associated lipochrome pigments 

 whose nature and amount determine the exact shade 

 of green displayed by the vegetative organs. In 

 flowering plants not only are the organs connected 

 with reproduction often brightly coloured, but the 

 vegetative organs themselves may also display 

 brilliant pigments. Among the pigments two series 

 are of special importance — these are first the lipo- 

 chromes, and second the anthocyans. Of the lipo- 

 chromes it is not necessary to say anything further 

 at present, but the anthocyans merit more detailed 

 consideration. 



Anthocyan, or the series of pigments included 

 under this name, occurs dissolved in the cell-sap, 

 and varies in colour from blue to red. It is an 

 exceedingly common pigment in the higher plants, 

 occurring alike in vegetative and reproductive organs, 

 and is readily soluble in water. By steeping the 

 rind of an apple or slices of beetroot in water, a red 

 solution of the pigment is readily obtained. If an 

 alkali such as caustic soda or ammonia be cautiously 

 added, the colour changes from red to blue, green, 

 and yellow successively. Finally, on adding excess 

 of alkali the solution becomes colourless. If the 

 alkali added be ammonia, this may be removed by 

 boiling, when the blue colour will once more reappear. 

 This change from red to blue is of course the litmus 

 reaction, so familiar to all who have worked in a 



