92 
NATURAL SELECTION. 
Chap. IV. 
effected by glands at tbe base of the stipules in some 
Leguminosae, and at the back of the leaf of the common 
laurel. This juice, though small in quantity, is greedily 
sought by insects. Let us now suppose a little sweet 
juice or nectar to be excreted by the inner bases of the 
petals of a flower. In this case insects in seeking the 
nectar would get dusted with pollen, and would certainly 
often transport the pollen from one flower to the stigma 
of another flower. The flowers of two distinct individuals 
of the same species would thus get crossed; and the act 
of crossing, we have good reason to believe (as will 
hereafter be more fully alluded to), would produce very 
vigorous seedlings, which consequently would have the 
best chance of flourishing and surviving. Some of these 
seedlings would probably inherit the nectar-excreting 
power. Those individual flowers which had the largest 
glands or nectaries, and which excreted most nectar, 
would be oftenest visited by insects, and would be 
oftenest crossed; and so in the long-run would gain 
the upper hand. Those flowers, also, wliich had their 
stamens and pistils placed, in relation to the size and 
habits of the particular insects which visited them, so as 
to favour in any degree the transportal of their pollen 
from flower to flower, would likewise be favoured or se¬ 
lected. We might have taken the case of insects 
visiting flowers for the sake of collecting pollen instead 
of nectar; and as pollen is formed for the sole object 
of fertilisation, its destruction appears a simple loss to 
the plant; yet if a little pollen were carried, at flrst 
occasionally and then habitually, by the pollen-devour¬ 
ing insects from flower to flower, and a cross thus 
effected, although nine-tenths of the pollen were de¬ 
stroyed, it might still be a great gain to the plant; and 
those individuals which produced more and more pollen, 
and had larger and larger anthers, would be selected. 
