114 THE STORY OF THE PLANTS. 



may also be well noticed in wild geraniums, and 

 less well in the strawberry, the dog-rose, and the 

 cinquefoil. 



In the present chapter, however, I propose to 

 go on to sundry flowers of the other great group 

 which has its parts in rows of three, and to 

 show how they have been affected by insect 

 visits. This will give us a clearer view of the 

 whole subject, while It will also form a general 

 introduction to systematic botany for those of 

 my readers who may be induced Jby this book to 

 carry their studies in this direction further. 



Before proceeding, however, there is one little 

 point I should like to note about the fivefold 

 flowers, which we shall find much more common 

 in the threefold, and among the wind-fertilised 

 species. This is the separation of the sexes in 

 different blossoms or even on separate plants. 

 All the flowers we have so far considered have 

 contained both male and female portions — have 

 been made up of stamens and carpels united 

 together in the self -same blossom. But many 

 of them, as you will recollect, have not been 

 actively both male and female at the same 

 moment. The stamens ripened ^.rst, the sensi- 

 tive surface of the carpels afterwards ; and this, 

 as we saw, tended to promote cross-fertilisation. 

 But if in any species all the stamens in certain 

 flowers were to be suppressed or undeveloped, 

 while in other flowers the same thing happened 

 to the carpels, self-fertilisation would become an 

 absolute impossibility, and every blossom would 

 necessarily be impregnated from the pollen of a 

 neighbour. Natural selection has accordingly 



