PLANT AFFINITIES 



It must be understood, however, that it is by 

 no means always possible to predicate, from 

 observation of a given pair of more or less 

 distantly related species, whether or not the two 

 would be mutually sterile. Sometimes the experi- 

 ment results in a surprise, and we are able to 

 produce offspring when the cross seemed alto- 

 gether improbable. 



Such was the case, it will be recalled, with 

 my experiments in hybridizing the dewberry with 

 the pollen of the apple and pear and rose and 

 mountain-ash. Such was the case also with the 

 cross which resulted in producing the sunberry, 

 and with that which developed the plumcot. 



In "each of these cases, to be sure, the pistil of 

 one plant accepted the pollen of the other, as it 

 were, unwillingly. But persistent effort effected 

 the desired resfult, and in the three instances 

 last mentioned fertile offspring were produced. 

 Possibly these might not have survived in the 

 state of nature, but under the conditions of 

 artificial selection they provided the foundation 

 for the development of what may fairly be con- 

 sidered new species. 



PLANT ANTAGONISMS 



The characteristics that make it impossible to 

 hybridize two species that have varied beyond 

 certain limits are sometimes physical. 



[43] 



