Ill THE COLOURS AND PIGMENTS OF PLANTS 65 



in shady places, in conditions unfavourable to the 

 development of much chlorophyll. 



Autumnal Coloration 



From this consideration of the common pigments 

 of the higher plants, we may pass to an account of 

 the peculiarities of the colours, selecting as examples 

 the colours of autumnal leaves and of flowers and 

 fruits. 



We are all in this climate familiar with the fact 

 that the chlorophyll of stems and leaves is short- 

 lived : we all know how the delicate yellow-green of 

 spring leaves deepens into the dark green of summer, 

 and then disappears in the yellows and reds of 

 autumn, while these in their turn lose their glory 

 before the chill blasts of winter. Chlorophyll is 

 bound up with the assimilating power of the plant, 

 and as this power diminishes, the chlorophyll which 

 is its outward expression disappears also. This is, 

 however, true only of the green colouring- matter, the 

 chlorophyll-green, and not of the associated pigments. 

 The chlorophyll-green is probably reabsorbed along 

 with starch and any other useful substances which 

 may be in the leaf, while the yellow xanthophyll 

 remains behind in the form of oily drops, set free by 

 the disintegration of the chlorophyll corpuscles. In 

 the simplest case, e.g. that of straw, there is thus 

 produced a uniform yellow coloration, the chlorophyll 

 being completely removed and the xanthophyll only 

 left. To produce the splendour of our October woods, 

 however, other factors have to be introduced. In 

 the first place the removal of the chlorophyll is often 



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