126 



GENETICS 



pure lines only. The average for each pure line is 

 given at the top of its column. When, for example, 

 beans weighing 60 eg. were selected from pure lines II, 

 VII, and XV, the average weights of their progeny 

 were 56.5, 48.2, and 45.0 eg. respectively, which in 

 each instance is nearer to the average for the pure 

 line than to the weight of the parental seed. 



It will be seen at once that the averages in the vertical 

 columns are nearer alike than the averages in the hori- 

 zontal columns. In other words, the beans bred true 

 to their pure line rather than to their fluctuating 

 parent. 



As a further example of this law, take the result 

 of selection for six years in pure line I as shown in 

 the accompanying table and in Figure 25. 



It is evident, for instance, that in 1907 the smallest 

 beans, weighing an average of 56 eg., gave an average 

 progeny weighing 69.07 eg., while the largest ones 

 for the same year, weighing an average of 81 eg., pro- 

 duced nearly the same average in their progeny as did 

 the smallest beans, that is, 67.66 eg. 



