572 Journal of Agricultural Research voi. xix. No. n 



Roguing the seed plot is the most important step in the production of 

 good seed. This consists in going over the field several times during 

 the season and removing undesirable hills. In the first place, there may 

 be variety mixtures in the seed plot. These mixtures are detected chiefly 

 by variations in foliage, color of blossoms, amount of blossoms produced, 

 and dates of ripening. There will also be some weak and degenerate 

 types and diseased hills to be removed. The plot should first be gone 

 over about blooming time, as variety mixtures are then very likely to be 

 most conspicuous. A group of hills may show blossoms that are off type 

 in color, or a certain group of hills may bloom more or less than the other 

 plants in the plot. These hills should be dug and the tubers removed 

 from the field. A little later the plot should be gone over again to catch 

 hills lacking in vigor or infected with disease. In early varieties, this 

 examination should be made just about the time the most vigorous vines 

 show signs of maturing. At this time some vines will be found fully 

 mature. This premature ripening is probably brought on by disease, 

 and the hills should be removed. Such hills most frequently appear at 

 random, but occasionally all the hills from a seed tuber may be diseased. 

 In looking for weak plants, the hills from each tuber should be studied 

 as a group. Weak hills will show a more crinkled foliage and usually 

 less vigorous vines. It is well to remember that the intermediate types 

 are the real trouble makers. They are usually as vigorous as normal hills, 

 but show a slight crinkling of the foliage and are very often of a lighter 

 shade of green. ^ In looking for these weak groups it is best not to work 

 too near the row being examined. First look each row over at close 

 quarters and then from two or three rows distant. In roguing out late 

 varieties, the work must always be done before the vines are touched 

 with frost. Remember that in roguing the tubers as well as the vines 

 must be dug and removed from the seed plot. 



If the seed plot has been carefully rogued, the entire crop may be 

 saved for seed. Occasionally a group of hills may produce tubers of 

 poor form, and these may be discarded. The small seed from such a 

 seed plot is just as satisfactory as the large, and in the great majority 

 of cases variations in form are nothing more than fluctuations and as 

 such are not transmitted to the following crop. 



In many instances the improvement secured by growing a variety in 

 a special seed plot of this kind for one season may be apparent for two 

 or three years after returning to the practice of selecting seed at ran- 

 dom from the field at digging time or from the bin; but permanent 

 improvement can be maintained only by continuing the special seed 

 plot year after year. With most varieties it is allowable, if the roguing 

 is carefully done, to increase the seed secured from the seed plot by 

 planting it in a certain part of the commercial field and then saving 



iWHIPPLB, O. B. DBGBNBRATION IN FOTATOSS. Mont. Agr. Exp. Sta. Bui. Z30, 39 p., 16 fig. 119x9. 



