The Inheritance of Quantitative Characters in Maize 15 
any particular character factors here, or say such and such a 
factor was contained by either variety. There is no doubt, how- 
ever, but that the presence (or the absence) of two factors of 
some kind or other in the pure condition causer! the one dent ear 
out of sixteen to breed true, and that the absence (or the 
presence) of these two factors in the pure condition caused the 
one flint ear out of sixteen to breed true. Furthermore, there is 
good evidence that factorial difference (without dominance) of 
more than tico allelomorphic pairs causes the difference in 
physical appearance of the starch in other maize varieties. 
From these facts, it is clear that one may give a valid Men- 
delian description to the behavior of those quantitative charac 
ters that give a blend in the Fj generation. Two adequately sup 
ported assumptions must be made; first, that dominance is absent 
and that two doses (i. e., the homozygous condition) of a factor 
have twice the effect of one dose ; second, that independent factors 
cumulative in their operation are paired with their absence in 
the hybrid. 
Let us assume a case of the so-called "blended" inheritance 
where all fluctuations due to environment are eliminated. A 
plant 12 inches tall is supposed to be crossed with a plant 28 
inches tall. The difference between them is 16 inches. Tf this 
difference is due to one allelomorphic pair in which dominance 
is absent, the F x generation is all intermediate — about 20 inches — 
and the F 2 generation falls into three classes in which two repre- 
sent the grandparental forms and one represents the F x form. 
Twenty-five per cent are 12 inches tall, fifty per cent are 20 inches 
tall, and twenty-five per cent are 28 inches tall. 
Again, let us suppose this 16-inch difference between the 
parents to be represented by two allelomorphic pairs instead of 
one. The ¥ 1 generation is again 20 inches tall, but instead of 
there being three classes in F 2 , there are five classes, viz., 12, 16. 
20, 24, and 28 inches, and they appear in the ratio 1:4:6:4:1. 
The grandparental types each appear once out of sixteen times 
The way this ratio is obtained is by simple recombination, but 
as dominance is absent, each time a single "presence" factor is 
radded. the height is increased four inches. 
f 1 AABB 
28 inches. 
24 inches. 
24 inches. 
20 inches. 
20 inches. 
16 inches. 
j - ;Ij±JB0 
I 4 AaBb 
f 1 AAbb 
\ 2 Aabb 
| 1 aaBB 
\ 2 aaBb 
20 inches. 
16 inches. 
12 inches. 
■1(1 aabb 
