72 COLOUR IN NATURE chap, hi 



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 ,^een 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, hsematoxylin, 

 etc. The pigments of Fungi are more numerous 

 than those of flowering plants and are little known. 



