Sept. I, 1920 



Line-Selection Work with Potatoes 



547 



other 5 years added to these performance records will go a long way to- 

 ward blotting out these apparent differences. It will be noted that all 

 these hills gave a very large increase over the control plots in 19 14. 

 But the interesting feature of the records is that following mass selection 

 in 1 9 14, the average yield of these lines immediately falls, in 191 5, to the 

 level of that of the control plot. In this connection it should be borne 

 in mind that these two varieties are very stable under conditions at the 

 Station and that neither has shown any serious tendency toward de- 

 generation. The increased production in 19 14 can not be accounted for 

 on the theory that degenerate or weak hills were com.mon in the control 

 plots in 1 9 14, nor can the decrease in yield in 191 5 be accounted for on 

 the theory that mass selection introduced into these lines degenerate 

 types which tended to lower the yield of 19 15. I believe the data clearly 

 indicate that hill selection brings only temporary increases in yield and 

 that such selection does not isolate high-yielding lines w^hich may be main- 

 tained as high-yielding population by mass selection based on tuber char- 

 acteristics alone. 



Table I. 



-Five-year summary of yields of inarkeiable tubers per acre from, hills selected 

 in I pi J 



Hill No. 



1916 



1918 



5-year 

 average. 



201 



202 



203 



204 



205 



206 



Average 

 Control. 



207 



208 



209 



210 



211 



212 



Average 

 Control . 



Pounds. 

 14, 764 

 19, 446 

 18, 409 

 19, 924 

 18, 207 

 13-839 



17.431 

 11,836 



14, 157 

 12,251 



18,513 

 17.936 

 17, 616 



18,315 



16, 464 



10, 257 



Pounds. 



13.350 

 12, 461 

 12, 543 

 10, 930 

 12, 947 

 11,898 



Pounds. 

 8.552 

 7.456 

 8,880 



8. 515 



7.572 

 7.744 



Pounds. 

 23. 580 



20, 537 

 23. 394 

 23. 464 

 18, 724 



18,353 



Pounds. 

 10, 849 



13.497 

 13, 660 



13.033 

 10,756 



12,354 

 12, 947 



8, 119 

 8,766 



21, 342 

 19. 143 



12,359 

 17.424 



11,823 



14,278 



9.873 

 8,566 

 8,826 



7. 700 



7.509 

 5.406 

 6, 969 

 6,218 



21,675 



19.514 

 22,511 

 20, 932 

 16, 090 

 20, 328 



14, 961 

 16,425 

 20, 490 

 15.007 

 21, 141 

 11,685 



10, 177 

 9,961 



6.525 

 6, 069 



20, 175 

 20, 16; 



16,618 



17,214 



Pounds. 

 14, 219 



14, 579 



15.377 

 15.173 

 13. 641 



12, 958 



14, 341 

 14, 023 



14, 025 



13. 574 

 15.671 

 13.731 

 15.918 



14, 507 



14, 571 

 12,733 



In 1916 work of similar nature was undertaken upon a more extended 

 scale. With the selection of 108 tuber units each of Green Mountain, 

 Rural New Yorker, and Early Six Weeks, 324 tuber lines were established, 

 which have now been carried through three seasons. Eight of these lines 

 were thrown out from the Early Six Weeks as variety mixtures, most of 

 the 8 being Early Rose, so the summary on this variety covers only 100 

 tuber lines. Rural New Yorker has been previously referred to as quite 

 417°— 20 3 



