INHERITANCE OF WAXY ENDOSPERM IN MAIZE. 57 
that the deviation is constitutional, as all the ears are near enough 
to the same ratio to be placed ina single group. This affords evidence 
that one of the factors for color is varying, and the rather definite 
deviation indicates that the change is in the nature of fractionation. 
Tf definite segregation of hereditary units 1s a fact, then the number 
of white seeds reappearing in the second generation of white x col- 
ored crosses will approximate certain percentages. If these per- 
centages are not approximated, two explanations are possible on the 
basis of equal segregation : 
(1) The predication of additional factors, inhibitors, and assumptions. By 
this method any percentage is possible, though when more than three factors 
are required it is seldom possible to test the explanation, since the number 
of individuals necessary to measure accurately small differences is extremely 
large. Immediate percentages may be explained by the use of additional fac- 
Pa age) /955. (985 -/9// /H2 
Fic. 7.—Diagram showing the relations of ears Nos. 1934, 1935, 19385, 1911, and 1912. 
tors, but in most cases it becomes impossible to reconcile the explanation with the 
behavior of the same individual in other combinations. Not infrequently in- 
dividual ears of maize are found that seem to fulfill certain comparatively 
simple explanations, but when the related pedigrees are analyzed a frequent 
result is to find incompatible individuals. 
(2) “ Failure of dominance” is the term often used to explain an excess of the 
recessive character, but this explanation will not serve when the recessive char- 
acter is deficient. If the fact that hereditary units undergo change during 
hybridization requires any further evidence than that presented by Castle and 
Phillips (2) this frequent “ failure of dominance” in generations succeeding the 
first would seem to furnish this evidence. If in a cross between a colored and a 
white plant the color proves to be dominant in the first generation, but in sub- 
sequent generations this complete dominance partially disappears, as it actually 
does, it seems natural to assume that either the color or the white, or both, 
have undergone some change, so that they do not stand as unalterably opposed 
as at first. In other words, a partial blend has taken place. Such a theory 
without doubt “strikes at the very heart of Mendelism,” but the facts as they 
are must be acknowledged. 
In demonstrating that an excess of white seeds is due to a failure 
of dominance the seeds bearing this character are planted, and upon 
