1 78 PLANT-BREEDING 



important one. The whole fruit-growing industry of 

 California amounts to an aggregate value of about sixty 

 millions of dollars annually, and of this sum hardly one per 

 cent is represented by the varieties imported or created by 

 Burbank. If we compare these figures with those given foi 

 the importance of the Burbank potato, we find a great differ- 

 ence. But for a fair appreciation we must realize that the 

 Wickson plum is scarcely older than the ten years required 

 for its first wide distribution and that most of the other hy- 

 brids created by Burbank are much younger. We must 

 leave it to the future to decide what will be the real signifi- 

 cance of the improvements in fruits and flowers, of which 

 this one man has produced such an astonishing number of 

 excellences. 



B. NEW VARIETIES OF FRUITS AND FLOWERS 

 Since the time of Darwin, the methods and achievements 

 of the breeders have played a large part among the argu- 

 ments adduced for the support of the doctrine of evolution. 

 In a broad sense they give us an insight into the processes by 

 which new forms are originated, and since the general laws 

 of variability must be the same for the cultivated condition 

 and for the phenomena of nature at large, there can be no 

 doubt about the general validity of the argument. The ex- 

 perience of the breeders teaches that new forms from time to 

 time arise from the existing ones. It gives a general idea 

 concerning the affinity of the parent types to their offspring, 

 showing the similarity to be very large and the produced 

 differences correspondingly small. On the other hand it 

 shows that by the accumulation of small differences, wider 

 divergences may be obtained. This evidence led Darwin to 

 one of the main propositions of his theory of evolution, viz., 

 that the larger groups in the vegetable kingdom have originat- 

 ed in the same way in which the smaller types are still seen 



