Ill THE COLOURS AND PIGMENTS OF PLANTS 67 



causes of the colours of flowers, for the three 

 processes already mentioned as the factors in the 

 production of autumnal coloration are precisely the 

 same as the processes which produce the colours of 

 flowers. If the tints of autumn arise naturally from 

 the check to vegetation produced by the first breath 

 of frost, then we may reasonably suppose also that 

 the colours of flowers are also in origin the natural 

 result of diminished vegetative power. 



Although in our climate the majority of our 

 plants shed their leaves in autumn in a cloud of 

 glory, yet we have of course some which retain their 

 leaves for several years, or do not shed them all 

 at once, being, as we say, evergreen. Even here, 

 however, the diminished vegetative power is frequently 

 seen in the partial modification of the chlorophyll. 

 The leaves of many evergreens assume a reddish 

 colour in winter, and this is due to the partial dis- 

 appearance of chlorophyll from the corpuscles, and 

 its replacement by red oily drops, probably of 

 lipochrome nature. These red drops disappear again 

 in spring when the leaves assume their normal green 

 colour. This red pigment differs from that of most 

 autumnal leaves in being confined to the chlorophyll 

 corpuscles, while in most cases a red colour is due to 

 anthocyan dissolved in the cell-sap. 



Colours of Flowers and Fruits 



The subject of autumnal coloration leads up to 

 the colours of flowers and fruits. These in the 

 general case are due either to an thocyan pigments 

 dissolved in the cell-sap, or to lipochrome pigments 



