VARIATION AND HEREDITY 



the preponder- 

 ating influence 

 of the immedi- 

 ate parents can- 

 not overcome 

 the cumulative 

 weight of the 

 mediocrity of 

 the more remote 

 ancestry. 



nnnnnannnn 



Pure Lines in 

 Heredity. Ap- 

 proaching the 

 problem from a 

 different angle, 

 a Danish biolo- 

 gist, Johanssen, 

 experimented 

 by measuring 

 the effect of se- 

 lection upon a 

 form in which 

 cross-fertiliza- 

 tion may be 

 eliminated. The 

 common garden 

 bean is adapted 

 for such an ex- 

 periment, since it is normally self -fertilized. He ac- 

 cordingly measured the breadth, length, and weight 



POPULATION 



FIG. 79. Diagrams showing five pure lines 

 and a population formed by their union. The 

 beans of each pure line are represented as assorted 

 into inverted test tubes making a curve of 

 fluctuating variability. Test tubes containing 

 beans of the same weight are placed in the same 

 vertical row. (From Walter, after Johanssen.) 



