94 PLANT-BREEDING 



types of races must be distinguished. In the first place, 

 those races which never become independent of continued 

 selection, and for which the seed must be produced anew 

 in each generation from a stock of so-called elite plants. 

 The other type embraces those varieties which after a short- 

 er or longer period of selection become self-dependent and 

 may henceforth be multiphed without special care. 



The prototype of the first kind is given by the sugar- 

 beets. Here the selection works with the ordinary char- 

 acters of the plant, the amount of sugar, the shape of the 

 roots, the properties of the foliage, and other features. No 

 chance, no sport has produced them, they are simply taken 

 as the plants are offering them everywhere. In consequence, 

 they remain dependent on selection, and though a mul- 

 tiplication during one generation without renewed polariza- 

 tion is often unavoidable, an intervention of two genera- 

 tions is but seldom allowed, and the lack of selection in 

 more than two generations would annihilate nearly all the 

 effect of the whole method. This type of selection is wholly 

 intra-specific and has no analogy whatever with the origin 

 of species in nature. 



The other type results in varieties which are as constant 

 and independent as the best horticultural sorts. In some 

 cases they are known to originate in the same way, by 

 accidental sports, as in the instance of Beseler's oats, losing 

 their needles. Here their comphance with the principle 

 of mutation is obvious. In the large majority of cases how- 

 ever, including the most widely known improvements of 

 cereals and other crops, they are said to have been produced 

 by the common, slow, and gradual process of selection. 

 All such cases are surrounded with doubt in regard to their 

 real origin, as well as concerning the degree of self-depend- 

 ency which is reached at the end. Often practical reasons 

 lead to the preferment of the original seed to one's own 



