Methods of Breeding and Improving the Potato Crop. 585 



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

 crop is treated. 



Making the second year's selections. When the breeding-plot nears 

 maturity the individuals should be examined and either the best and 

 healthiest vines inarked or, if easier, the diseased vines showing weak- 

 ness marked, so that they can be discarded later. Then dig each tuber- 

 unit as in the preceding year, placing the tubers from each four-hill 

 unit 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. Following the same method as used the first 

 year, select from the breeding-plot the fifty best tuber-units, and pre- 

 serve 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 i-i, 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 selected the first year, and the second number, that following the 

 hyphen, refers to the number of the tuber unit selected from this progeny 

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

 was the second tuber-unit selected in the first year and the second 2 

 indicates that it is 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- 

 plot not selected should be retained for planting a multiplication-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 preceding 

 year, go over the product of each select tuber-unit and pick out the ten 

 best tubers of each for the next year's planting. 



Continuing Selections in Third Year 



In the third year, the fifty selections of heavy yielding tuber-units 

 should be planted by the same methods used the second year, at least 



