Ill THE COLOURS AND PIGMENTS OF PLANTS 55 



that either pigment or coloration can be of direct 

 use. When we come to consider the phenomena of 

 colour in organisms whose relations to other organisms 

 are extremely complex, we shall find that there is 

 a constant tendency to look for the cause or the 

 justification of the colour phenomena in these complex 

 relations. It is therefore important to realise that it 

 is illogical to seek for a complete explanation of 

 colour phenomena in complex organisms while those 

 of relatively simple ones remain unexplained. 



Chlorophyll and the Associated Pigments 



This brief account of the colours of the plants not 

 containing chlorophyll must suffice, for it is impossible 

 here to go into further details. We shall treat the 

 colours and colouring -matters of the chlorophyll- 

 containing plants in greater detail, for in them the 

 colours are as a whole more striking and beautiful, 

 and the pigments are much more fully known. 



In these plants chlorophyll is of course by far the 

 most important pigment, and sometimes indeed the , 

 only one. For details as to its chemical characters 

 reference must be made to the text-books, but we 

 may here recall one or two points as to its occurrence. 

 Chlorophyll occurs, generally speaking, in all plants 

 except the Fungi ; it is especially abundant in the 

 leaves or vegetative organs, and occurs in associa- 

 tion with definite parts of the cell protoplasm — the 

 chlorophyll corpuscles. It is frequently associated 

 with other pigments which may mask it, or may 

 replace it in special regions of the plant. This 

 partial replacement is especially noticeable in the 



