406 
TROPICAL NATURE 
VI 
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 
