Neo-Mendelism 71 



feet. In inheritance of course the 6.5- and 5. 5-foot 

 plants behave exactly alike; the same is true of 6-foot 

 plants. It must be evident, therefore, that a classi- 

 fication of F 2 individuals on the basis of the number of 

 doses might well be slightly obscured. If outside influ- 

 ences were lacking, the F 2 situation could be represented 



FIG. 17. Diagram illustrating distribution of phenotype classes 

 in an F 2 population from cross involving cumulative factors. Practically 

 same diagram as fig. 16, and interpreted in same way; short rectangle 

 at left indicates that very few plants of population contain maximum 

 number of doses; short rectangle at right indicates that very few plants 

 contain minimum number of doses; plants with intermediate number of 

 doses most numerous, as indicated by tall rectangle in middle (see also 

 fig. 18). 



by fig. 17, or better, fig. 18; but when outside influences 

 are active, it may be represented by fig. 19. It will be 

 seen from this last diagram that not all individuals 

 belonging to a particular size class may have the same 

 number of doses; that is, conditions for a smaller-dosed 

 individual may be so much better than those for a larger- 

 dosed individual that they may exchange size classes in 



