THE MODERN POTATO PROBLEM 225 



The former may be oxygen of the air and the latter the 

 carbon dioxide produced by the tuber's respiration. 

 Other methods that have been found effective in short- 

 ening the rest period, such as treating the tubers with 

 certain gases, probably do so by rendering the skins 

 more permeable to oxygen or carbon dioxide. However, 

 this does not explain how the tubers finally come out of 

 their rest period without help. Nature does not remove 

 their jackets. 



DEGENERATION OF POTATOES. When we start with 

 a potato plant grown from a seed and use the tubers for 

 its propagation, each succeeding crop really represents 

 an annual growth of our original plant. This may be 

 made clearer by comparing the seedling potato plant 

 with a young apple tree. Every summer the tree 

 produces a large number of buds which remain dormant 

 until the following spring, when they give rise to a new 

 crop of shoots. The potato plant likewise produces 

 dormant buds on the tubers, which are large fleshy 

 underground shoots, or stems. By the annual death 

 of the vines the tubers are separated from the parent 

 plant whose life is perpetuated by the tubers. If we 

 imagine each succeeding crop of tubers, like the apple 

 shoots, becoming a permanent part of the parent plant, 

 we would have a giant potato plant often many years 

 old. Are these giant potato plants, known as varieties, 

 immortal, or are they subjected to old age and final 

 death the same as animals? At first thought this 

 mi^ht seem an easy question to answer, but scientists 

 still hold divergent views about it. 



Degeneration of potatoes is a well-established fact. 



