False Atavism 197 



as to prevent cross-pollination by the visits of 

 bees. 



This purification must be done in nearly every 

 generation. The oldest varieties are to be sub- 1. 

 jected to it as well as the latest. There is no 

 regular amelioration, no slow progression in the 

 direction of becoming free from these admix- 

 tures. Continuous selection is indispensable to 

 maintain the races in the degree of purity which 

 is required in commerce, but it does not lead to 

 any improvement. Nor does it go so far as to 

 become unnecessary in the future. This shows 

 that there must be a continuous source of im- 

 purities, which in itself is not neutralized by 

 selection, but of which selection can only elim- 

 inate the deteriorating elements. 



The same selection is usually applied to new 

 varieties, when they occasionally arise. In this 

 case it is called '' fixing," as gardeners gener- 

 ally believe that through selection the varieties 

 are brought to the required degree of purity. 

 This belief seems to rest mainly on obser- 

 vations made in practice, whereas we have seen, 

 isolation is of very rare application. Most va- 

 rieties would no doubt be absolutely pure from 

 the first moment of their existence, if it were^ 

 only possible to have them purely fertilized. 

 But in practice this is seldom to be obtained. 

 Ordinarily the breeder is content with such slow 



