260 Fertilisation and Hybridization 



perience teaches, however, that in these cases the descen- 

 dants of the hybrids do not display that multifariousness 

 of type, nor those splittings that are characteristic of 

 variety-hybrids. They usually all resemble each other 

 and their parents, the original hybrids, and this constancy 

 persists through the course of generations. Accordingly 

 there originate races of hybrids which, apart from their 

 possibly diminished fertility, can hardly be distin- 

 guished from true species. Sometimes they are found 

 wild, as for example a hybrid race between two Alpine 

 roses and other races of the kind in the genera Anemone, 

 Salvia, Nymphaea, etc. Sometimes they have been ob- 

 tained artificially or have accidentally originated in the 

 gardens. The genus Oenothera is exceptionally rich in 

 such hybrid races, especially in the sub-genus of the com- 

 mon evening-primroses, Onagra. Very frequently such 

 hybrids are simply described as species, on the one hand 

 because they can be reproduced, without deviation, from 

 seeds, and on the other hand because systematic works 

 frequently do not sufficiently consider the elementary 

 species. The distinguishing of the latter from hybrid 

 races is frequently by no means easy. 



The purpose of my explanations compels me to restrict 

 myself to simple and clear cases. In nature these occur 

 relatively rarely, and the individual elements of the phe- 

 nomena are usually commingled in most motley variety. 

 By far the greater number of crossings take place between 

 parents whose mutual relations do not wholly fit either 

 the one or the other concept, but where the characteristics 

 of the different types of hybrids are intermingled. I 

 cannot consider these cases here; they are of too com- 

 plicated a nature for an address. 



Only one point I wish to touch upon. In the preceding 



