6o 
COLOUR IN NATURE 
CHAP. 
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 
