68 The Potato 



for comparison to plant about every tenth row with unselected 

 seed of the same variety, cut and planted in the same way, but 

 without reference to keeping each tuber separate. The production 

 of these check-rows will show whether progress is being made in the 

 selection. 



Cultivate the breeding plot and treat it otherwise just as an ordi- 

 nary crop is treated. 



Making the second year's selection. — Wlien the breeding plot 

 ncars maturity, the individuals should be examined and either the 

 best and healthiest vines marked or, if easier, the diseased vines 

 showing weakness marked, so that they can be discarded later. 

 Then dig each tuber-unit as in the preceding year, placing the tubers 

 from each four-hills together at the side of the row. Each unit should 

 then be weighed and the number of large, medium and small sized 

 tubers recorded. This will enable the breeder to determine which of 

 the original fifty tuber-units selected in the first year has given the 

 largest average yield in the ten tuber-units or forty-hill test, and 

 this is the primary test of the value of the original selection. Follow- 

 ing the same method as used the first year, select from the breeding- 

 plot the fifty best tuber-units, and preserve the tubers of each unit 

 separately in a paper bag. The majority of the selection in this 

 year should naturally be made from those rows which have given 

 the highest yield. Number the tuber-units selected in this second 

 generation 1-1, 1-2, 1-3, etc., and 2-1,2-2, etc. In such hyphenated 

 numbers the first figure refers to the number of the tuber-unit se- 

 lected the first year, and the second number, that following the 

 hyphen, refers to the number of tuber-units elected from this prog- 

 eny the second year. Thus in the case of 2-2, the first 2 indicates 

 that it was the second tuber-unit selected in the second year from 

 progeny of unit No. 2 of the first year's crop. In the third year the 

 numbers can be extended by the same principle, the tuber-units 

 selected from progeny 2-2 in the third year being numbered 2-2-1, 

 2-2-2, 2-2-3, etc. These numbers can be placed on the bags and 

 notes on weight of yield, number of tubers per unit, etc., recorded 

 under the same number. 



All of the good tubers from the remaining tuber-units of the 

 breeding-[)lot not selected should be retained for planting a multi- 

 plication-plot the third year, which should furnish sufficient seed for 

 planting the general crop for the fourth year. 



At some convenient period before planting time, as in the pre- 



