28 



CIKCULAK NO. 113, BUREAU OF PLANT INDUSTEY 



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while the weak plants averaged but- 1.1 ounces. The significance of 

 these data is fully realized only when considered- 

 in its relation to the use of large or small tubers 

 for seed purposes. It is readily seen that but 

 a very small proportion, if indeed any, would 

 be included in the use of tubers weighing 5 

 ounces or over, whereas in the use of small 

 tubers the proportion of small tubers from the 

 weak plants w^ould be, relatively speaking, much 

 greater. Herein lies the danger in the use of 

 small potatoes from unselected seed stock. 



The accompanying reproductions of photo- 

 graphs shown in the top row of figure 1 repre- 

 sent strong and weak plants of two tuber units 

 of the Rural Blush potato in 1911 . These plants 

 w^ere produced from apparently identical tubers, 

 were grown in the same row, and w^ere subjected 

 in every particular to identical cultural condi- 

 tions. The reproductions in the middle row^ 

 represent the tubers produced by these plants, 

 while the lower set represent tne tubers pro- 

 duced in 1912 from five tuber units of the 1911 

 crop. The 1912 crop is divided into two classes, 

 according to size. The tubers on the left in 

 each illustration consist of those weighing 3 

 ounces or over. These are designated as mer- 

 chantable or prime tubers, while those on the 

 right are the culls. 



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SEED-SELECTION PLAT. 



■3 The accompanying diagram (fig. 2) of a plant- 

 I ing plan is presented more as a suggestion for 

 .1 use by boys' and girls' potato clubs than for 

 ^ the average potato grower. A hundred tubers 

 ^ make a convenient unit to handle, which at the 

 ^ same time is capable of unlimited expansion in 

 the hands of those whose enthusiasm makes 

 them willing to undertake larger operations. 



Each tuber unit in the diagram is numbered 

 in order to facilitate note taking, as well as the 

 keeping of a record on the behavior of each 

 individual tuber unit throughout the season. 

 By affixing their numbers to the units selected 

 for another season's trial it is possible to pre- 

 serve the identity of each selection throughout whatever period 

 of years it may be studied. 



[Cir.. 113] 



