26 CIRCULAR NO. 113, BUREAU OF PLANT INDUSTRY. 



secutively in the row at a distance of from 10 to 14 inches apart, 

 according to the character and moisture content of the soil. By 

 allowing an additional spacing between each set of fours the four 

 plants from each tuber are definitely isolated from adjoining ones 

 and the grower can readily observe any variation in vigor and uni- 

 formity between the various units planted. It also enables him to 

 detect any mixtures which may be present in the variety. If a 

 potato planter with a fertilizer-distributing attachment is available, 

 it may be used to open the furrows and drop the fertilizer by simply 

 removing the covering disks and setting the plow a little deeper. 



The seed pieces may be covered with a plow if care is exercised 

 not to displace them. During the growing season such observations 

 as are indicated in the accompanying form of Note Blank I should 

 be recorded (Table I). All units which do not satisfy the require- 

 ments of a good strain, such as uniformity of type in habit of 

 growth and character of foliage and size of plant, should be marked 

 as undesirable units. This constitutes the first step in both the 

 selection and elimination processes. At digging time the product 

 of each unit is separately harvested by hand and a further selection 

 made from the marked or surviving units. Only such units should 

 be retained for further trial as most nearly approach the desired 

 ideal, which in this case is uniformity in size, shape, and productive- 

 ness. The tubers from each selected unit are collectively placed in 

 separate sacks, preferably in cotton or burlap. Heavy manila paper 

 bags may be used, but there is always danger of their being torn. 

 Before being placed in storage, each sack should be numbered with 

 the varietal and tuber-unit number, in order to preserve its identity 

 in the field notes. The final examination should consist of notes, 

 recorded on the note blank, of the number and weight of merchant- 

 able and unmerchantable tubers. From each of the units not re- 

 jected at this time select 10 of the best tubers for the next season's 

 planting. It is desirable, though not absolutely essential, to main- 

 tain the study of each selection on the tuber-unit basis, because it 

 permits a more accurate comparison of the behavior of each. The 

 10 selected tubers from each original unit will give 40 plants for 

 study the second year. As in the previous season, notes should be 

 taken on the growing plants, recording them on Note Blank II 

 (Table I) . All selections which do not produce a reasonably uni- 

 form lot of plants should be marked for rejection. Each selection 

 should be harvested separately, as in the previous year, and such as 

 do not meet the requirements imposed should be rejected. The fur- 

 ther conduct of the work will consist in the multiplication of the 

 selected strains for field planting and the elimination of any weak 

 plants that may occur during this process. 



[Cir. 113] 



