LUTHER BURBANK 



origin of the fittest (or at least one possible origin) 

 appeared to be explained by the existence of such 

 a hybrid as the Primus Berry. 



The parents of the Primus berry, it will be 

 recalled, were the California dewberry (Rubus 

 ursinus) and the Siberian raspberry (Rubus cra- 

 taegifolius). Not only are these forms so differ- 

 ent in appearance that no botanist would ever 

 think of denying that they belong to totally dif- 

 ferent species, but the fact that one of them is 

 indigenous to California and the other to Siberia 

 gives what might be called geographical support 

 to the opinious of the classifiers. Few indeed are 

 the forms of animal or plant life inhabiting the 

 Eastern and the Western Hemispheres that are 

 recognized as specifically identical. 



The same genera are represented on both con- 

 tinents, because the remote progenitors of all races 

 of animals and plants of the Northern Hemisphere 

 were once inhabitants of a common territory in 

 the region of the North Pole. But there has been 

 no opportunity for the mingling of Asiatic and 

 American forms of plant life since the separation 

 of the continents, until civilized man in very recent 

 time began to transport forms of animal and plant 

 life across the oceans. 



There had been no communication since a 

 remote geological era — ^probably not since the last 



[180] 



