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- 

 fulWhy 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 



