No. 565] CHANGES PRODUCED BY SELECTION 41 



individual showed a mean of 26.9 ± .06 leaves, and from 

 among them plants having 25 and 29 leaves, respectively, 

 were selected to start the minus and the plus lines. These 

 two mother plants gave F 7 populations alike as to mean, 

 but differing by one class as to mode. The minus line 

 had the higher mode. The extremes of this generation 

 used in carrying on the experiment differed by 8 leaves, 

 and the resulting progenies apparently followed the selec- 

 tion. The means are 25.6 ± .07 and 28.2 ± .09 leaves. 

 Whether these shifted means represent a permanent 

 change or not we are not prepared to say. The minus 

 mean is probably somewhere near the correct figure for 

 in the F 9 generation it was practically the same, but in 

 the F 9 generation of the plus strain the mean dropped 

 from 28.2 ±.09 leaves to 26.7 ± .13 leaves. This is a 

 slightly lower point than that of the original F 5 distribu- 

 tion, but it was calculated from only 76 individuals. A 

 conservative estimate of the significance of the results 

 would probably be as follows: the mean of the minus 

 strain has shifted slightly but permanently and is now 

 fixed, while the mean of the plus strain has not changed 

 but has shown evidence of some heterozygosis in one gen- 

 eration. 



We come finally to consider Families No. 27 and No. 82, 

 the data on which are listed in Tables XIV and XV. Two 

 generations of both plus and minus selection were re- 

 corded for Family No. 27, but only plus selections of 

 Family No. 82 were grown. There is no necessity for 

 considering either in detail because a simple inspection of 

 the tables shows that selection has accomplished nothing. 



Conclusions 



The cumbersome and no doubt dry details of the ex- 

 periments to the close of the year 1912 having been de- 

 scribed, let us give a brief resume of the conclusions that 

 we believe may reasonably be drawn from the data that 

 have been offered. There can be no doubt that the orig- 

 inal "Halladay" type of tobacco, isolated and propa- 



