hi THE COLOURS AND PIGMENTS OF PLANTS 65 
in shady places, in conditions unfavourable to the 
development of much chlorophyll. 
J 
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, eg. 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 
F 
