104 



GENETICS 



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

 VII, and XV, the average weights of their progenj^ 

 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. 



Weight of 

 Cent,- parent «eed 



10 20 30 40 » 60 70 10 20 30 10 50 60 70 10 20 SO 40 50 60 70 10 20 }0 40 SO 60 70 ;0 20 50 40 SO SO 70 



Pure line number 



n 



w 



w 



M 



Fig. 34. — The result of selection in four pure lines of beans. The verti- 

 cal columns, representing the average progeny from different sized 

 parents all derived from the same pure line, contain groups nearer 

 aUke than the horizontal columns, representing progeny from the 

 same sized parents, but different pure lines. All the numbers indicate 

 centigrams. Data from Johanssen. 



It will be seen at once that the averages in the 

 vertical columns are nearer alike than the averages 

 in the horizontal 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 



