Summary. 
7 
dominant, independently inherited factors. The segregation 
into three plants with indeterminate habit to one with determinate 
habit accompanied by an increased range of variation in height 
of both classes of segregates, when a short pole bean is crossed 
with a tall bush bean or a tall pole bean with a short bush bean, 
are, therefore, interpreted by a combination of the single-factor 
and the multiple-factor hypotheses, or by what may be termed a 
modified multiple-factor hypothesis, the modification consisting 
merely in the assumption of inequality in dominance and in- 
equality in potency between the factors. One dominant factor is 
assumed to determine habit of growth and therefore to have a 
much greater potency in the determination of plant height than 
the two or more other, nondominant factors. 
It is argued that this modified multiple-factor hypothesis 
affords a more simple and direct interpretation of the results 
in bean crosses than does the hypothesis of a single unit-difference 
between all pole and bush beans, which necessitates the further 
assumption that the unit-factor is modified commonly, tho 
irregularly, in crosses between pole and bush beans. 
