96 The Potato 



mands now made iipon the plant. The yield of tubers 

 has been enormously increased above that of the wild 

 plant. Many shapes and colors have been discarded to 

 keep the few which suit the eyes of civilized men. The 

 length of the life of the potato plant has been shortened 

 from nine months or more in the wild state to only three 

 or four months. Vast numbers of seedling varieties 

 which may have possessed greater natural vigor have 

 been discarded to keep those which possess these quali- 

 ties. It is not surprising therefore that the potato plant 

 is not a strong one. One period in its life is especially 

 precarious. The cultivated plant now produces much 

 less seed than the wild plant, some kinds seldom or never 

 blossoming ; but blossoming is still a demand upon the 

 strength of the potato. In the wild state the tubers were 

 set after the seed formation. Under domestication the 

 life of the plant has been shortened and the two processes 

 overlap. When this time comes in hot weather, as with , 

 the late main crop of the northern states, the heat and . 

 drought which occur so often make the poorest possible 

 conditions for the potato. Insects, diseases and careless _ 

 methods of cultivation often further reduce the vitality 

 of the crop. This has been called the "critical period" 

 of the life of the potato. If it is passed in high vigor, the 

 potato has later a more or less indeterminate growth. 

 That is, there is no clearly defined time for its maturity, 

 as with grain crops, but instead it gradually weakens, all 

 the time increasing the yield of tubers. This condition 

 occurs but seldom in the United States on account of the 

 heat of summer, but it is an ideal towards which potato 

 growers should strive. Production of a high degree of 

 vitality in the growing plant in its early life and good 

 soil conditions and care during the hot weather, will carry 



