COLOURS OF PLANTS. 235 



and Orchideoe. The same laws as to the conditions of a 

 maximum production of colour are thus found to obtain 

 both in plants and animals. 



Relation of the Colours of Flowers and their Geo- 

 graphical Distribution, The adaptation of flowers to be 

 fertilized by insects often to such an extent that the 

 very existence of the species depends upon it has had 

 wide-spread influence on the distribution of plants and 

 the general aspects of vegetation. The seeds of a 

 particular species may be carried to another country, 

 may find there a suitable soil and climate, may grow 

 and produce flowers ; but if the insect which alone can 

 fertilize it should not inhabit that country, the plant 

 cannot maintain itself, however frequently it" may be 

 introduced or however vigorously it may grow. Thus 

 may probably be explained the poverty in flowering- 

 plants and the great preponderance of ferns that distin- 

 guishes many oceanic islands, as well as the deficiency 

 of gaily-coloured flowers in others. This branch of the 

 subject is discussed at some length in my Address to the 

 Biological Section of the British Association, 1 but I may 

 here just allude to two of the most striking cases. New 

 Zealand is, in proportion to its total number of flowering- 

 plants, exceedingly poof in handsome flowers, and it is 

 correspondingly poor in insects, especially in bees and 

 butterflies, the two groups which so greatly aid in 

 fertilization. In both these aspects it contrasts strongly 

 with Southern Australia and Tasmania in the same 

 latitudes, where there is a profusion of gaily -coloured 

 flowers and an exceeding rich insect-fauna. The other 

 case is presented by the Galapagos islands, which, though 



1 See Chapter VII. of this volume. 



