Sept. 1, 1920 Line-Selection Work with Potatoes 549 



Since these small seed pieces give an average of only about 1% 

 stems per hill, the thinning is not a very great task. Careful records 

 are kept of the number and weight of marketable tubers and culls. 

 Yields are computed upon the basis of a perfect stand. Naturally this 

 favors the plot \vith an imperfect stand, for a missing hill tends to raise 

 the yield of adjacent hills. Stand records are kept, showdng the position 

 of missing hills. As yet there is no basis upon which to apply such 

 records in correcting yields, but I hope to make use of these later. Careful 

 notes are also kept upon vine characteristics. We are particularly inter- 

 ested in those that indicate degeneration. Three general types of vines — 

 vigorous, semi-curlydwarf or with curlydwarf tendencies, and curly- 

 dwarfs — are recognized. 



The results of three seasons' work upon this project are presented here, 

 not with the idea of proving the presence or the absence of high-yielding 

 tuber lines within these 316 selections but rather for the purpose of call- 

 ing attention to the difficulty of interpreting these performance records. 

 If such a method of seed improvement is to be of real and practical 

 value, especially in the hands of the average potato grower, it would 

 seem that a 3-year test should give rather definite and dependable 

 results. If the process is to be a longer one than this, then the method 

 should be proposed for the potato specialist rather than for the rank 

 and file of potato growers. 



GREEN MOUNTAIN TUBER LINES 300 TO 408 



In variety tests at this Station, the Green Mountain types have 

 on an average given the highest yields of all varieties grown. Varieties 

 belonging to this group have, however, varied rather widely in yields. 

 They are more susceptible to scab, more inclined to degeneration, and 

 produce tubers less desirable as to commercial form than the Rural 

 New Yorker; but withal the type is a very promising main-crop commer- 

 cial potato. 



In Table II will be found the 3-year performance records of the 108 

 Green Mountain lines, expressed in yields of pounds per acre. Of the 

 three groups of tuber lines, these have given the most noticeable varia- 

 tions in yields. 



I/ine 332 ranks first mth a 3-year average yield of 27,849 pounds per 

 acre, while line 344 has a 3-year average of 3,841 pounds. When ranked 

 on 3-year average tuber production by weight, the 20 highest-yielding 

 lines assembled in the last column of Table III have given an average 

 yield of 25,000 pounds per acre, while the 20 lowest-ranking, appearing 

 in the last column of Table IV, have averaged 12,083 pounds. 



In Tables III and IV it will be noticed that only a few of the lines 

 appear as consistent high or low yielders. Several numbers will be 

 found in both tables, showing that lines have swung from one extreme 

 to the other. 



