Systematic and Sexual Relationship. 593 



The simplest form to wliicli it lias hceii ])r»)])()Se(l to 

 rediKse the parallel hetween systematic and sexual rela- 

 tionship, is the following: (1) Plants which i)n)(luce 

 offspring when crossed with one anc^ther, always belong 

 to the same genus; (2) Plants whose fertility is not 

 diminished in crossing belong to the same systematic 

 species (or collective species). Both generalizations are 

 in great favor and are defended by ])rominent investi- 

 gators. They have, however, a weak side, viz.. that they 

 cannot be reversed. 



Let us first examine the former proposition. It de- 

 nies the existence of hybrids between distinct genera, 

 or so-called generic hybrids. It originated amongst those 

 philosophers who regarded the genera as having been 

 created, the species, however, as having arisen from them 

 by natural means. We have already dealt with the his- 

 torical significance of these transmutationists in the fir.st 

 vohime (p. 17). To them the view, stated above, is also 

 due, that not only do species arise within the genera by 

 a normal process of evolution, but that new forms may 

 arise from these species by crossings. W. Herbert is 

 the most famous representative of this view.-^ which was 

 later defended by Godron. The latter investigator de- 

 scribes all genera, the species of which are fertile with 

 those of related genera as artificial, and has collected a 

 mass of evidence in support of this view.^ 



No fundamental objection can be brought against this 

 view, and its adoption would lead in relatively few cases 



^W. Herbert, AmaryUidaccac, With a Treatise Upon Cross-bred 

 Vegetables, London 1837". pp. 337 et seq. See also Gartner, loc. cit . 

 p. 152, and Nageli, Sitcungsber. d. k. bayr. Akad. d. Wiss., Dec. 15. 

 1865, P- 400- 



"" A. Godron, Dc Vespcee et des raees dans les ctres organises. 1850. 

 Vol. I, pp. 225-236. and ^fe}n. Acad. Stanislas a Nancy, 1S62. pp. 2<>6- 

 29R. 



