266 -  ‘PROPICAL NATURE u 
leaves standing up like great candelabra. Sometimes the 
ground is carpeted with large flowers, yellow, pink, or white, 
that have fallen from some invisible tree-top above ; or the air 
is filled with a delicious perfume, the source of which one seeks 
around in vain, for the flowers that cause it are far overhead 
out of sight, lost in the great overshadowing crown of verdure.” 
Although, as has been shown elsewhere, it may be 
doubted whether light directly produces floral colour, there 
can be no doubt that it is essential to the growth of vegeta- 
tion and to the full development of foliage and of flowers. 
In the forests all trees, and shrubs, and creepers struggle 
upwards to the light, there to expand their blossoms and 
ripen their fruit. Hence, perhaps, the abundance of climbers 
which make use of their more sturdy companions to reach 
this necessary of vegetable life. Yet even on the upper 
surface of the forest, fully exposed to the light and heat of 
the tropical sun, there is no special development of coloured 
flowers. When from some elevated point you can gaze down 
upon an unbroken expanse of woody vegetation, it often 
happens that not a single patch of bright colour can be dis- 
cerned. At other times, and especially at the beginning of 
the dry season, you may behold scattered at wide intervals 
over the mottled-green surface a few masses of yellow, white, 
pink, or more rarely of blue colour, indicating the position of 
handsome flowering trees. 
The well-established relation between coloured flowers 
and the need of insects to fertilise them may perhaps be con- 
nected with the comparative scarcity of the former in the 
equatorial forests. The various forms of life are linked to- 
gether in such mutual dependence that no one can inordi- 
nately increase without bringing about a corresponding increase 
or diminution of other forms. The insects which are best 
adapted to fertilise flowers cannot probably increase much 
beyond definite limits, because in doing so they would lead to 
a corresponding increase of insectivorous birds and other 
animals which would keep them down. The chief fertilisers 
—bees and butterflies—have enemies at every stage of their 
growth, from the egg to the perfect insect, and their numbers 
are, therefore, limited by causes quite independent of the 
supply of vegetable food. It may, therefore, be the case that 
