116 PROPAGATION OF PLANTS. 



be. It may be said, however, that while certain species 

 oj^a gen^sjnay have sufficient affinity to admit of hybrid- 

 izing, others do not. Among some kinds of fruits 

 hybrids have been produced between widely separated 

 and very distinct species, as, for instance, between the 

 Black Cap Raspberry (Rubus occidentalis) , and the 

 European Raspberry (R. Idceus). The late Charles 

 Arnold, of Canada, produced several such hybrids, 

 although they were of no value for cultivation. In view 

 of what has already been accomplished in the way of 

 hybridizing and crossing, and the small number of per- 

 sons who have experimented in this field, it would be 

 mere presumption on the part of any one to attempt to 

 determine the limits of such operations. It is generally 

 supposed, however, that the hybridizer is restricted in his 

 operations to the members of a genus that is, he can 

 only produce hybrids between the species of the same 

 genus, and a genus is simply a group of species all pos- 

 sessing similar generic characteristics. But, as I have 

 already shown, the species of a single genus some- 

 times resist all attempts to force them to intermingle or 

 hybridize, and it is quite probable that they are as far 

 removed from each other in relationship as the members 

 of some distinct genera. It is also probable that in some 

 instances botanists have made mistakes in. the grouping 

 of species, as well as in their separation or designation. 

 It is certainly quite possible thafc two species supposed 

 to belong to a different genera may be forced to inter- 

 breed ; in fact, hybrids between two supposed-to-be distinct 

 genera are already known, and a hybrid Palm, the Micro- 

 phmnix sahuti, is quite a recent production of this kind. 

 The experimenter need not hesitate to attempt the 

 hybridizing of the species of closely allied genera, 

 although it is quite probable thafc in a large majority of 

 instances it will be but a waste of time. 



