Chap. V. HETEROSTYLED PLANTS. 243 



how prepotent the legitimate pollen from a short-styled 

 plant was over the illegitimate pollen from a long-styled 

 plant. 



In all the several foregoing points the parallelism is 

 wonderfully close between the effects of illegitimate 

 and hybrid fertilisation. It is hardly an exaggeration 

 to assert that seedlings from an illegitimately fer- 

 tilised heterostyled plant are hybrids formed within 

 the limits of one and the same species. This conclu- 

 sion is important, for we thus learn that the difficulty 

 in sexually uniting two organic forms and the sterility 

 of their offspring, afford no sure criterion of so-called 

 specific distinctness. If any one were to cross two 

 varieties of the same form of Lythrum or Primula for 

 the sake of ascertaining whether they were specifically 

 distinct, and he found that they could be united only 

 with some difficulty, that their offspring were extremely 

 sterile, and that the parents and their offspring re- 

 sembled in a whole series of relations crossed species 

 and their hybrid offspring, he might maintain that his 

 varieties had been proved to be good and true species; 

 but he would be completely deceived. In the second 

 place, as the forms of the same trimorphic or dimorphic 

 heterostyled species are obviously identical in general 

 structure, with the exception of the reproductive 

 organs, and as they are identical in general constitu- 

 tion (for they live under precisely the same condi- 

 tions) the sterility of their illegitimate unions and that 

 of their illegitimate offspring, must depend exclusively 

 on the nature of the sexual elements and on their in- 

 compatibility for uniting in a particular manner. And 

 as we have just seen that distinct species when crossed 

 resemble in a whole series of relations the forms of the 

 same species when illegitimately united, we are led to 

 conclude that the sterility of the former must likewise 



