74 The Potato 



tive of the opinion held by most of the European experi- 

 menters. "And the real degeneration, an ageing of a 

 variety, which has been under uniformly favorable condi- 

 tions and of which good seed is used has not been pro\'ed 

 and is improbable." 



Varieties seem to differ in their staying qualities. 

 Some have held up for 50 to 60 years, while others have 

 passed out quickly. The old Peachblow variety which 

 was widely grown forty years ago has largely run out 

 now except in certain localities like the Carbondale region, 

 where it has been given careful selection and is better 

 to-day than ever before. 



Another reason ascribed is that long-continued bud 

 propagation results in an inner physiological weakening. 

 It is difficult to see, however, how prolonged asexual 

 propagation affects stocks injuriously. 



What appears to be the running out of a variety may, 

 in some instances, be due to a change in market demands 

 and the varieties disappearing which do not meet these 

 demands. For example, the old long Burbank has 

 given place to the more round varieties such as the Rural, 

 and the Blue Victor has been replaced by white varieties 

 and has now practically gone out of existence. Fru- 

 wirth believes that a lack of adaptation to local condi- 

 tions results in a degeneration of certain varieties. Poor 

 attention to the selection of seed tubers is also suggested 

 as a cause of deterioration. Fruwirth summarizes the 

 opinions of a number of German experimenters in sup- 

 port of these two views. 



East points out that perhaps the potato requires 

 frequent crossing to keep up the vigor, and that possibly 

 continual propagation by asexual methods causes a loss 

 of heterozygosis. 



