72 
COLOUR IN NATURE 
CHAP. Ill 
according to Zopf, represented by the ubiquitous 
lipochromes ; and even the fifth group is mentioned 
by Zopf as being represented among the Fungi. It 
is curious that in spite of the fact that chlorophyll is 
such a complex pigment, and can be made to yield 
numerous coloured derivatives in the laboratory, 
there is no evidence that in natural conditions any 
of the plant pigments are produced by its decom¬ 
position. The assertion that the xanthophyll of 
leaves is derived from it has been repeatedly made, 
but not on any good grounds. 
As to the primary meaning of chlorophyll in 
metabolism we know nothing. Macallum seems to 
believe that it is in some way directly connected with 
the nuclear chromatin. 
As to the lipochromes, we know neither their 
primary meaning nor their proximate use. They 
are perhaps universally distributed in plants, and 
occur in association with reserves in the shape of oil 
and fat. They are probably always either yellow or 
orange, the pure red lipochromes not occurring in 
plants, and these yellow lipochromes are perhaps 
invariably found in association with fat. We have 
already seen that Ehring regards the carotin of the 
tomato as a cholesterin fat. 
The remaining pigments are probably all of the 
nature of waste or useless substances. Among them 
are included the anthocyans, the colouring-matters 
of bark, and of some woods like brasilin, haematoxylin, 
etc. The pigments of Fungi are more numerous 
than those of flowering plants and are little known. 
