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 
