312 THE STRUCTURE OF FLOWERS. 



They are true for at least the first few years ; as in but four 

 or five cases only did he exceed the third generation ; 

 and when he prolonged them to seven generations, as in 

 Mimulus luteus, and ten in Ipomcea purpurea, his results 

 began to assume a very different complexion. 



The inference deducible fi-om his experiments is that 

 careful and artificial crossing generally introduces a remark- 

 able stimulus for a time; but the effects are not permanent. 

 On the other hand, a perseverance in self -fertilisation pro- 

 duces results which are much more stable ; so that, finally, 

 self-fertilised plants (i.e the successive off-spring of this 

 process) outstrip their competitors. Florists also find that by 

 continued crossing the flowers of a species they soon reach 

 the end of their tether, and no further progress is obtainable. 



Secondly, ]Mr. Darwin failed to realize the fact that self- 

 fertilisation predominates in nature with the vast majority of 

 hermaphrodite plants, whether they be adapted to insects or 

 are inconspicuous and adapted for autogamy. 



Thirdly, he misinterpreted the meaning of degeneracy, 

 which often accompanies self-fei-tilisation ; thinking that it 

 involved constitutional injuriousness, of which there is no 

 trace whatever in nature. 



Lastly,* he, and other writers who have followed him, 

 wrongly inferred that adaptations to insect agency implied 

 a converse " purpose," viz. to avoid self -fertilisation, instead 

 of regarding them as the inevitahle results of the stimulus of 

 intercrossing and of the visits of insects. The danger of 

 this a 'priori, deductive, or teleological reasoning, without any 

 attempt at verification, lies in the fact that it is untrust- 



* I must refer the reader to my paper on The Self-fertilisation of 

 Plants, in which I have dealt with these points. It was written in 1877, 

 but I have met with nothing since to invalidate the above conclusions, 

 but, on the contrary, very much in support of them. 



