178 



effected than were those at Svalof and at Gissleberga where the soils were 

 better suited to withstand the conditions indicated. The following table 

 gives the results for this year and is self-explanatory: 



Yields cf tubers and per cent starch cf different sorts grown en different soils in the 

 cold, wet year cf 1907 (24 p. 219). 



Degeneration The problem of potato improvement by the selection of favorable varia- 

 in potatoes. t i ons is i n ti ma tely linked with that of "degeneration." That potatoes 

 degenerate or "run out" naturally is an idea commonly held by the great 

 mass of growers. Many believe that this is a natural phenomenon some- 

 thing to be expected and something which cannot be avoided. A new 

 variety comes into circulation, remains in the foremost ranks for a few years 

 or until it reaches a period of old age or "senility" and then gradually begins 

 to decline. Such is the generally accepted idea of the life of a potato sort. 

 That certain varieties do appear to act in this peculiar manner cannot be 

 disputed. On the other hand, experience shows that other sorts which have 

 been under cultivation a great many years do not appear to have lost in 

 vigor or in productive qualities during this long space of time. A good 

 example is afforded by the Swedish sort known as Dala, commonly grown in 

 the province of Delecarlia (Dalarne). This potato is said to have been 



