VI. 



THE COLOURS OF PLANTS AND THE ORIGIN 

 OF THE COLOUR-SENSE. 



Source of Colouring matter -in Plants Protective Coloration and Mimicry 

 among 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 Beautiful 

 Why allied species of Flowers differ in Size and Beauty Absence of 

 Colours in Wind-fertilized 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 the 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. 



THE colouring of plants is neither so varied nor so com- 

 plex 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 different 

 plants ; they have different chemical reactions ; they are 



