Ill 
THE COLOURS AND PIGMENTS OF PLANTS 
7i 
species of orchids, and on the corolla of the foxglove. 
There seems little doubt that these markings are in 
many cases employed by insects as landmarks in 
their search for honey, and they have been in con¬ 
sequence termed honey-guides. In many cases, how¬ 
ever, they are much more complex than seems 
necessary for this function, and are by no means 
limited to flowers containing honey ; their meaning 
and origin are still very doubtful. 
Meaning of Plant Pigments and Summary 
Looking at the colours of flowers and fruits as a 
whole, we may say that all the processes which give 
rise to their brilliant colours have a parallel in the 
vegetative shoot. The prominence of lipochromes 
and the development of anthocyan are paralleled in 
the autumnal coloration of leaves. The development 
of a white colour is paralleled by the occasional 
partial albinism of leaves, which occurs either as a 
result of injury by other organisms, or in some 
instances as a natural condition, eg. in the lung¬ 
wort ( Pulmonaria ). Even the complex markings of 
petals are dimly foreshadowed in the veining of 
leaves. 
All this is fairly obvious, but when we attempt 
to discuss further the prime meaning of colour in 
plants, the difficulties are very great. Of the five 
groups of pigments described in the last chapter, we 
have in plants the first represented by chlorophyll ; 
the third possibly represented by the anthocyan 
pigments, which are apparently derived from tannins, 
and are probably useless substances ; the fourth, 
