406 TROPICAL NATURE 



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 fertilise 

 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 distinguishes many oceanic islands, as well as 

 the deficiency of gaily -coloured flowers in others. New 

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

 plants, exceedingly poor in handsome flowers, and it is cor- 

 respondingly poor in insects, especially in bees and butterflies, 

 the two groups which so greatly aid in fertilisation. In both 

 these aspects it contrasts strongly with Southern Australia 

 and Tasmania in the same latitudes, where there is a profu- 

 sion of gaily -coloured flowers and an exceeding rich insect- 

 fauna. Another case is presented by the Galapagos islands, 

 which, though situated on the equator off the west coast of 

 South America, and with a tolerably luxuriant vegetation in 

 the damp mountain zone, yet produce hardly a single con- 

 spicuously-coloured flower; and this is correlated with, and 

 no doubt dependent on, an extreme poverty of insect life, not 

 one bee and only a single butterfly having been found there. 



Again, there is reason to believe that some portion of the 

 large size and corresponding showiness of tropical flowers is 

 due to their being fertilised by very large insects and even 

 by birds. Tropical sphinx-moths often have their probosces 

 nine or ten inches long, and we find flowers whose tubes or 

 spurs reach about the same length, while the giant bees, and 

 the numerous flower-sucking birds, aid in the fertilisation of 

 flowers whose corollas or stamens are proportionately large. 



Recent Views as to direct Action of Light on the Colours of 

 Flowers and Fruits 



The theory that the brilliant colours of flowers and fruits 

 are due to the direct action of light has been supported by a 

 recent writer by examples taken from the arctic instead of 

 from the tropical flora. In the arctic regions vegetation is 

 excessively rapid during the short summer, and this is held 

 to be due to the continuous action of light throughout the 



