VI 
THE COLOURS OF PLANTS AND THE ORIGIN OF THE 
COLOUR-SENSE 
Source of Colouring Matter in Plants — Protective Coloration and Mimicry 
in Plants — Attractive Colours of Fruits — Protective Colours of 
Fruits — Attractive Colours of Flowers — Attractive Odours in Flowers 
— Attractive Grouping of Flowers — Why Alpine Flowers are so beauti- 
ful — Why Allied Species of Flowers differ in size and beauty — Absence 
of Colour in Wind-fertilised Flowers — The same Theory of Colour 
applicable to Animals and Plants — Relation of the Colours of Flowers 
and their Geographical Distribution — Recent Views as to Direct 
Action of Light on the Colours of Flowers and Fruits — On the Origin 
of the Colour-sense : Supposed increase of Colour-perception within 
the Historical Period — Concluding Remarks on the Colour-sense. 
Source of Colouring Matter in Plants 
The colouring of plants is neither so varied nor so complex 
as that of animals, and its explanation accordingly offers 
fewer difficulties. The colours of foliage are, comparatively, 
little varied, and can be traced in almost all cases to a special 
pigment termed chlorophyll, to which is due the general green 
colour of leaves ; but the recent investigations of Mr. Sorby 
and others have shown that chlorophyll is not a simple green 
pigment, but that it really consists of at least seven distinct 
substances, varying in colour from blue to yellow and orange. 
These differ in their proportions in the chlorophyll of differ- 
ent plants ; they have different chemical reactions ; they are 
differently affected by light ; and they give distinct spectra. 
Mr. Sorby further states that scores of different colouring 
matters are found in the leaves and flowers of plants, to some 
of which appropriate names have been given, as erythrophyll, 
which is red ; and phaiophyll, which is brown ; and many of 
