8 INTRODUCTORY REMARKS. CHAP. L 



truth and generality of the law, so as to insist on it 

 and impress their belief on others. 



In 1862 I summed up my observations on Orchids 

 by saying that nature " abhors perpetual self-fertilisa- 

 tion." If the word perpetual had been omitted, the 

 aphorism would have been false. As it stands, I 

 believe that it is true, though perhaps rather too 

 strongly expressed; and I should have added the 

 self-evident proposition that the propagation of the 

 species, whether by self-fertilisation or by cross-fertili- 

 sation, or asexually by buds, stolons, &c. is of paramount 

 importance. Hermann Miiller has done excellent 

 service by insisting repeatedly on this latter point. 



It often occurred to me that it would be advisable 

 to try whether seedlings from cross-fertilised flowers 

 were in any way superior to those from self-fertilised 

 flowers. But as no instance was known with animals 

 of any evil appearing in a single generation from the 

 closest possible interbreeding, that is between brothers 

 and sisters, I thought that the same rule would hold 

 good with plants ; and that it would be necessary at 

 the sacrifice of too much time to self-fertilise and inter- 

 cross plants during several successive generations, in 

 order to arrive at any result. I ought to have re- 

 flected that such elaborate provisions favouring cross- 

 fertilisation, as we see in innumerable plants, would 

 not have been acquired for the sake of gaining a 

 distant and slight advantage, or of avoiding a distant 

 and slight evil. Moreover, the fertilisation of a flower 

 by its own pollen corresponds to a closer form of inter- 

 breeding than is possible with ordinary bi-sexual 

 animals; so that an earlier result might have been 

 expected. 



I was at last led to make the experiments recorded 

 in the present volume from the following circumstance^ 



