62 The Potato 



tion, growers were working blindly without knowing how 

 or when or even whether they were going to reach a sta- 

 bility of type. On the other hand the method of pedi- 

 greed culture or "individual selection" eliminated the 

 fear of failure because of the appearance of the hitherto 

 unsurmountable variations. 



Plants which have any desired characteristics in com- 

 mon may differ widely in their ability to transmit these 

 characters. It is generally impossible for the cultivator 

 to determine, from the appearance of any given progeny, 

 the most invariable and the most like its parent; but it 

 may be said those individuals which grow up in the most 

 usual or normal environments are most likely to perpet- 

 uate themselves. A very unusual condition, as of soil, 

 moisture or exposure, is not easily imitated when provid- 

 ing for the succeeding generation, and a return to normal 

 conditions of environment may be expected to be followed 

 by a more or less complete return to normal attributes 

 on the part of the plant. If the same variation, therefore, 

 were to occur in plants growing under widely different 

 conditions, the operator who wishes to preserve the new 

 form should take particular care to select his tubers from 

 those individuals which seem to have been least influenced 

 by the immediate conditions in which they were grown. 



The method of individual selection or pedigree breed- 

 ing is now universally accepted by the best breeders. 

 In potato-breeding it is known as the "tuber-unit" 

 method, that is, the progenies of individual tubers are 

 tested for a niunber of years to determine the best pure 

 lines which are constant from year to year. 



One of the first and best methods of breeding potatoes 

 by the tuber-unit or pedigree plan has been devised by 

 H. J. Webber. This method is so satisfactory, when 

 properly carried out, that it is given here in detail : 



