CHAPTER XI 



THE SPECIAL COLOURS OF PLANTS : THEIPv. ORIGIN 



AND PURPOSE 



The general colour relations of plants — Colours of fruits — The meaning of 

 nuts — Edible or attractive fruits — The colours of flowers — Modes of 

 securing cross-fertilisation — The interpretation of the facts — Summary 

 of additional facts bearing on insect fertilisation — Fertilisation of 

 flowers by birds— Self-fertilisation of flowers — Difficulties and con- 

 tradictions — Intercrossing not necessarily advantageous — Supposed 

 evil results of close interbreeding— How the struggle for existence 

 acts among flowers — Flowers the product of insect agency — Concluding 

 remarks on colour in nature. 



The colours of plants are both less definite and less complex 

 than are those of animals, and their interpretation on the 

 principle of utility is, on the whole, more direct and more 

 easy. Yet here, too, we find that in our investigation of the 

 uses of the various colours of fruits and flowers, we are 

 introduced to some of the most obscure recesses of nature's 

 workshop, and are confronted with problems of the deepest 

 interest and of the utmost complexity. 



So much has been written on this interesting subject 

 since Mi\ Darwin first called attention to it, and its main 

 facts have become so generally known by means of lectures, 

 articles, and i)0})ular l:)ooks, that I shall give here a mere 

 outline sketch, for the purpose of leading up to a discussion 

 of some of the more fundamental problems which arise out of 

 the facts, and which have hitherto received less attention than 

 they deserve. 



