132 THE BEAUTIES OF NATURE CHAP. 
from the tip; which, when the insect subse- 
quently visited a long-styled flower, would 
again come just opposite to the head of the 
pistil. Hence we see that by this beautiful 
arrangement insects must carry the pollen of 
the long-styled form to the short-styled, and 
vice versa. 
The economy of pollen is not the only 
advantage which plants derive from these 
visits of Insects. A second and scarcely less 
important is that they tend to secure “ cross 
fertilisation’; that is to say, that the seed 
shall be fertilised by pollen from another 
plant. The fact that “cross fertilisation” is 
of advantage to the plant doubtless also 
explains the curious arrangement that in 
many plants the stamen and pistil do not 
mature at the same time — the former having 
shed their pollen before the pistil 1s mature ; 
or, which happens less often, the pistil having 
withered before the pollen is ripe. In most 
Geraniums, Pinks, etc., for instance, and 
many allied species, the stamens ripen first, 
and are followed after an interval by the 
pistil. 
