204 



MULTIPLE FACTORS 



the convincing experiments of Johannsen on the size 

 of the Princess beans. The material is highly fav- 

 orable for work of this kind, not only because exact 

 measurements may be taken, but because the stocks 



FIG. 62. I. Five pure lines of beans (A, B, C, D, E), and the popula- 

 tion (A-E) that results when they are mixed. II. The upper figure repre- 

 sents the original biotype, and the two figures below this, the two new 

 biotypes that arose from it. (After Johannsen.) 



reproduce by self-fertilization and were found to be 

 homozygous. Johannsen's results (Fig. 62) show 

 that no matter how many factors influence the size 

 of the bean, so long as the bean is homozygous, selec- 

 tion of plus and minus variants produces no effect on 



