THE MODERN POTATO PROBLEM 231 



reasons, sterility in the flowers of potatoes is the rule 

 rather than the exception that is, potato seeds are 

 rarely produced. The cause of this phenomena is being 

 investigated with the view of bringing it under control 

 in breeding work. Another difficulty is the fact that 

 most varieties of potatoes are already hybrids possess- 

 ing latent characteristics of their wild ancestors. These 

 undesirable characters are liable to crop out and be- 

 come dominant in the seedlings, so it is necessary to 

 grow a large number of plants from which to select the 

 ones desired. The increasing prevalence of diseases is 

 also adding greatly to the almost insurmountable diffi- 

 -culties of the potato breeder. On account of difficulties 

 involved and the expert technique required, to say noth- 

 ing of the expense, potato breeding cannot be generally 

 practised as a method of potato improvement. How- 

 ever, important improvements of potato varieties have 

 been made by this method and the outlook is very prom- 

 ising for further improvements. Some attempts are 

 being made to breed strains that will propagate them- 

 selves just as well by seeds as by tubers. If this can 

 be accomplished, it will result in great saving in the price 

 of seed and in the elimination of diseases that are carried 

 in and on infected tubers. 



. The second method intended to improve existing 

 varieties is by selection. The procedure is to propa- 

 gate from a single tuber, or from desirable hills selected 

 in the field. Selection methods have been extensively 

 used and are still practised, although it has not been 

 definitely proved that our existing varieties can be 

 much improved by these methods. The chief benefits 



