328 
DARWINISM 
CHAP. 
How the Struggle for Existence Acts among Flowers. 
Let us now consider what will he the action of the struggle 
for existence under the conditions we have seen to exist. 
Everywhere and at all times some species of plants will he 
dominant and aggressive ;• while others will he diminishing in 
numbers, reduced to occupy a smaller area, and generally 
having a hard struggle to maintain themselves. Whenever 
a self-fertilising plant is thus reduced in numbers it will be 
in danger of extinction, because, being limited to a small 
area, it will suffer from the effects of too uniform conditions 
which will produce weakness and infertility. But while this 
change is in progress, any crosses between individuals of 
slightly different constitution will be beneficial, and all varia¬ 
tions favouring either insect agency on the one hand, or 
wind-dispersal of pollen on the other, will lead to the pro¬ 
duction of a somewhat stronger and more fertile stock. In¬ 
creased size or greater brilliancy of the flower, more abundant 
nectar, sweeter odour, or adaptations for more effectual cross- 
fertilisation would all be preserved, and thus would be initiated 
some form of specialisation for insect agency in cross-fertil¬ 
isation ; and in .every different species so circumstanced the 
result would be different, depending as it would on many 
and complex combinations of variation of parts of the flower, 
and of the insect species which most abounded in the district. 
Species thus favourably modified might begin a new era 
of development, and, while spreading over a somewhat wider 
area, give rise to new varieties or species, all adapted in 
various degrees and modes to secure cross-fertilisation by 
insect agency. But in course of ages some change of condi¬ 
tions might prove adverse. Either the insects required might 
diminish in numbers or be attracted by other competing 
flowers, or a change of climate might give the advantage 
to other more vigorous plants. Then self-fertilisation with 
greater means of dispersal might be more advantageous; the 
flowers might become smaller and more numerous ; the seeds 
smaller and lighter so as to be more easily dispersed by the 
wind, while some of the special adaptations for insect fertilis¬ 
ation being useless would, by the absence of selection and by 
the law of economy of growth, be reduced to a rudimentary 
