The Theory of Sexual Selection. 407 
form most effectual for spreading out the leaves to the 
light and air. Here, then, we likewise find that the 
cause determining plant beauty is natural selection; 
and so we may conclude that the only reason why 
the forms of trees which are thus determined by 
utility appeal to us as beautiful, is because we are 
accustomed to these the most ordinary forms. Our 
ideas having been always, as it were, moulded upon 
these forms, esthetic feeling becomes attached to 
them by the principle of association. At any rate, it 
is certain that when we contemplate almost any forms 
of plant-structure which, for special reasons of utility, 
differ widely from these (to us) more habitual forms, 
the result is not suggestive of beauty. Many of the 
tropical and un-tree-like plants—such as the cactus 
tribe—strike us as odd and quaint, not as beautiful. 
Be this however as it may, I trust I have said enough 
to prove that in the vegetable world, at all events, the 
attainment of beauty cannot be held to have been an 
object aimed at, so to speak, for its own sake. Even 
if, for the purposes of argument, we were to suppose 
that all the forms and colours in the vegetable world 
are due to special design, there could be no doubt 
that the purpose of this design has been in chief part 
a utilitarian purpose ; it has not aimed at beauty ex- 
clusively for its own sake. For most of such beauty as 
we here perceive is plainly due to the means adopted 
for the attainment of life-preserving ends, which, of 
course, is a metaphorical way of saying that it is 
probably due to natural selection’. 
1 The beauty of autumnal tints in fading leaves may possibly be 
adduced ger contra. But here we have to remember that it is only 
some kinds of leaves which thus become beautiful when fading, while, 
