132 THE BEAUTIES OE 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 versct. 



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 is 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 aftor an interval by the 

 pistil. 



