28 MAINE AGRICULTURAL EXPERIMENT STATION. I915. 



selected plant and that its deviation in that direction was equal 

 to one-third the deviation of the mother plant. 



Attention should also be called to the fact that if the devia- 

 tion of the daughter rov^ is in the same direction and greater 

 than the deviation of the selected plant the index will be nega- 

 tive. Further if the deviation of the daughter row is in the 

 opposite direction and greater than the deviation of the 

 mother plant the index will have a value greater than 2. 



These indices may be treated as other statistical constants. 

 Thus, if there is no effect of selection within the pure line 

 these indices, on the average, will be equal to i.o within the 

 limits of chance deviations. If there is an effect of the selec- 

 tion the average index will be significantly less than i.o. On 

 the other hand, if the average index is significantly greater 

 than 1.0 it will indicate that there is a tendency for the devia- 

 tion to swing in the direction opposite to the selection. 



In calculating these indices the deviations of the plants and 

 the rows expressed as percentages of their means have been 

 used instead of the absolute deviations. In this way these in- 

 dices take account of both the factors discussed at the begin- 

 ning of this section. 



Indices have been calculated to show the effect of each of 

 the three selections upon the rows grown in each of the suc- 

 ceeding years. The average index for both the plus and minus 

 selections and for all the rows grown in each year is given in 

 Table 8. Probable errors for the mean index have been cal- 

 culated from the distributions of all the indices for each year. 



Table 8. 



Showing the Mean Index of Selection for the Plus and Minus 



Selections and for All the Rows, for Each Year. 



Selection Made in 



Rows 

 grown in 



Mean Index. 





+ selections. 



— selections. 



All selections. 



1911.. 



1912 

 1913 

 1914 

 1913 

 1914 

 1914 



1.1575 

 1.3051 

 1 .0053 

 0.9509 

 1.0151 

 1.0285 



1.1556 

 .0.8910 

 0.8532 . 

 0.9615 

 1 .0100 

 1.0102 



1.1566± .1442 



1911 



1911 



1.0932 ±.1.522 

 0.92,50 ± .0491 



1912 



1912.. 



0.9568 ±.0241 

 1 .0126± .0139 



1913 



1.0197 ±.0221 







