230 LUTHER BURBANK 



potato ball, the Burbank rose was developed only 

 after numerous hybridizing experiments in which 

 new blood was introduced, and new qualities 

 were brought into the combination. 



Among other roses, the strains of which were 

 mingled with those of the offspring of the Her- 

 mosa to produce the Burbank, was the Bon 

 Silene. And there were at least three or four 

 others that are similarly to be credited, although 

 the exact pedigrees of all of them are not mat- 

 ters of record. 



Still the initial impulse to variation which sup- 

 plied the material for the new hybridizings, and 

 was thus primarily responsible for the outcome, 

 was given by the seeds gathered from the Her- 

 mosa. The same tendency to increased vigor 

 and productivity and variation that we saw 

 manifested in the case of the potato, and to 

 which reference has been made also in the case 

 of the sugar cane, and of other plants that are 

 usually propagated by division rather than by 

 cross-fertilization, was doubtless given the seeds 

 of the rose by a chance mingling of just the 

 right kind of pollen brought by some vagrant 

 bee with its usually unreceptive ovules. 



The lesson that cross-fertilization gives vigor, 

 and provides the materials for variation, which 

 we have seen emphasized so many times, is here 



