CHAPTER XI 
THE SPECIAL COLOURS OF PLANTS : THEIR 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 Mr. Darwin first called attention to it, and its main 
facts have become so generally known by means of lectures, 
articles, and popular books, 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. 
