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 contradictions--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.