BURBANK'S HORTICULTURAL NOVELTIES 219 



Leaving our sketch of the historical evidence given by 

 Burbank concerning his hybrids, some points of biological 

 interest remain to be mentioned. In the first place, crosses 

 are by no means always successful. The result depends 

 mainly upon the affinity of the chosen parents. Whenever 

 their systematic differences are too great, the cross will be 

 infertile, or at least the produced hybrids will refuse fertil- 

 ization, even with the pollen of their parents. Repeated 

 crosses are impossible and no practical results can be ob- 

 tained. Or all the hybrids may be of inferior quality, not 

 promising any improvement and thus are not worthy of 

 further culture. Of this, Burbank gives an instance in an 

 experiment with a Californian dewberry. He transplanted 

 a specimen of this indigenous species into his garden, isolated 

 it, and brought to its blossoms the pollen of almost all its 

 allies he had at that time under cultivation. He gave it 

 the pollen of brambles and raspberries, of strawberries and 

 roses and even of cherries, apples, and pears. All the seed 

 was saved in a mixture and a strange lot of hybrids arose 

 from them the next spring. Some repeated well known 

 types, but many seemed full of promise of new forms. At 

 the blooming period, many defaulted, making no flowers at 

 all, and the remainder proved to be utterly sterile; no single 

 hybrid could be chosen by which a new strain could be 

 obtained. 



A parallel instance is that of the Nicotunia. This is 

 Burbank's name for a hybrid he once won between a tobacco 

 plant and a Petunia. The parents are so distant that, as a 

 rule, the cross never results in good seeds. Among hundreds 

 of seedless capsules, he found one in a better condition, and 

 from its contents raised one single plant. This, however, 

 was an annual and absolutely sterile and so the experiment 

 ended with its death. 



A last point which we have to discuss is the interest 



