CHAP. I. INTRODUCTORY REMARKS 3 



few plants seeni to be invariably self-fertilised ; yet 

 even these retain traces of having been formerly 

 adapted for cross-fertilisation. These exceptions need 

 not make us doubt the truth of the above rule, any 

 more than the existence of some few plants which pro- 

 duce flowers, and yet never set seed, should make us 

 doubt that flowers are adapted for the production of 

 seed and the propagation of the species. 



We should always keep in mind the obvious fact 

 that the production of seed is the chief end of the 

 act of fertilisation ; and that this end can be gained 

 by hermaphrodite plants with incomparably greater 

 certainty by self-fertilisation, than by the union of 

 the sexual elements belonging to two distinct flowers 

 or plants. Yet it is as unmistakably plain that innu- 

 merable flowers are adapted for cross-fertilisation, as 

 that the teeth and talons of a carnivorous animal are 

 adapted for catching prey ; or that the plumes, wings, 

 and hooks of a seed are adapted for its dissemination. 

 Flowers, therefore, are constructed so as to gain two 

 objects which are, to a certain extent, antagonistic, and 

 this explains many apparent anomalies in their struc- 

 ture. The close proximity of the anthers to the stigma 

 in a multitude of species favours, and often leads, to 

 self-fertilisation ; but this end could have been gained 

 far more safely if the flowers had been completely 

 closed, for then the pollen would not have been injured 

 by the rain or devoured by insects, as often happens. 

 Moreover, in this case, a very small quantity of pollen 

 would have been sufficient for fertilisation, instead of 

 millions of grains being produced. But the openness 

 of the flower and the production of a great and ap- 

 parently wasteful amount of pollen are necessary for 

 cross -fertilisation. These remarks are well illustrated 

 by the plants called cleistogamic, which bear on the 



B 2 



