26 SUCCESSFUL FARMING 



the field planting. Greater progress will be made by keeping the tubers 

 from selected hills separate and testing these as new strains. Each should 

 have a number by which it will always be known. The first year ten 

 hills of each might be planted in rows side by side with the parent variety 

 every third place. The best only should be saved and the next and suc- 

 ceeding years the plats may be made larger. 



Tuber unit selection should start with selected tubers of the same 

 size which are desirable in appearance and free from disease. These are 

 each cut into four pieces, which are planted in succession, one tuber after 



VARIATION IN YIELD OF POTATOES FROM SELECTED 



the other, with some space between the hills from the different tubers. 

 When mature, the four hills from a tuber are dug together and the future 

 selection based upon the yield of tubers and their appearance. These 

 must be designated by numbers as in other selection work. The next 

 year single row plats of ten or more hills each of the most promising may 

 be planted, with the parent variety in every third plat as before. 



Potatoes may be improved in productiveness, disease resistance and 

 quality of tubers. There is a difference in susceptibility, especially to 



1 Courtesy of Pennsylvania Agricultural Experiment Station. 



