64 
COLOUR IN NATURE 
CHAP. 
an hour the part of the epidermis still in contact 
with the leaf became decolorised, while the severed 
portion completely retained its colour. As the 
chlorophyll can hardly be supposed to have a direct 
effect on the anthocyan, Molisch concludes that the 
“ conditions for the formation of alkaline substances 
must be especially favourable in chlorophyll-con¬ 
taining cells.” This is a conclusion of great interest 
and importance. If cells which contain much chloro¬ 
phyll also contain strongly alkaline substances, and 
therefore, as we may reasonably suppose, tend to 
destroy any anthocyan pigment which may be 
formed, then this is equivalent to saying that the 
conditions which are favourable to the development 
of chlorophyll are unfavourable to the development 
of anthocyan, and vice versa. This is a very tempt¬ 
ing conclusion, for it seems to explain many points 
in the distribution of anthocyan which have hitherto 
been very puzzling. Broadly speaking, anthocyan 
tends to appear conspicuously in many leaves and 
shoots in early spring, in many leaves in autumn, in 
flowers, and in fruits. Its function is often said in 
the case of vegetative organs to be the protection of 
chlorophyll from the injurious effects of excessive 
light, but this does not account for its appearance in 
autumnal leaves. If, however, we may assume that 
chlorophyll and anthocyan are in antithesis to one 
another, we can readily understand why the latter 
should appear in spring, before the power of assimi¬ 
lation is completely established, in autumn when it 
is beginning to disappear, in ripening flowers and 
fruits where it is more or less completely lost, and 
also in the leaves examined by Stahl which grew 
