308 LUTHER BURBANK 



We have seen that there is possibility of hy- 

 bridization between forms that are a shade more 

 widely separated, in which case the hybrid off- 

 spring have the appearance of new species, but 

 lack fertility. Such instances were presented in 

 the hybrid colony of offspring of the dewberry 

 fertilized by pollen from the apple and pear and 

 mountain ash and rose; also by the hybrid be- 

 tween strawberry and raspberry. 



These strange hybrids would clearly enough 

 have been entitled to recognition as new species 

 had they been able to reproduce themselves. But 

 their sterility reduced them to the rank of mules 

 to make comparison with the most familiar in- 

 stance of an infertile hybrid in the animal world. 



From these sterile hybrids the Sunberry dif- 

 fers fundamentally in that it is if anything more 

 prolific than either of its parents. 



Meantime the Sunberry differs from the hy- 

 brids of another and more familiar type that arise 

 from the union of parents that are so closely 

 related that cross-pollenizing is easily effected 

 between them. Such hybrids, of which we have 

 seen many examples crosses between the differ- 

 ent daisies, between black and white blackber- 

 ries, thorny and thornless briers, stone-seed and 

 stoneless plums, and sundry others follow, as 

 we know, a characteristic line of development. 



