The Inheritance of Quantitative Characters in Maize 105 
is that in three of them the F x plants were almost as tall as the 
tall parent and in the fourth were considerably taller than the 
mean of the two parents. That this increase in height of F x 
plants over the mid-parental height is in no case ascribable to 
dominance of tallness over shortness, but is due rather to in- 
creased vigor accompanying heterozygosis, is indicated by the 
fact that in every case the mean height of the F 2 plants is about 
half-way between the heights of the parents and is also shown 
by the lack of skewness in the F 2 frequency distributions. 
Practically all of the F 2 fraternities overlapped in height the 
inner extremes of their parents. Most of them had a range of 
from near the mean height of one parent to the mean height of 
the other parent and in one cross the F 2 range was from the 
minus extreme of the short parent to the plus extreme of the 
tall parent. The F 3 families were very diverse in height and in 
variability. Few F 3 families were as tall as the tall parent and 
none was quite so short as the short parent, tho the latter was 
approached very closely in a few cases. In case of some of the 
extreme F ?j lots, the variability was sufficient to make it probable 
that types like the parents could be isolated in the next genera- 
tion. Moreover, certain F ?> families with heights variously inter- 
mediate between the parents had variabilities small enough to 
indicate the possibility of their breeding true to these heights. 
In some of these crosses, the height of plants was separated 
into its components — number of nodes and internode length. 
In number of nodes the F x families were strictly intermediate 
between the parent varieties and the mean number of nodes in 
F 2 was practically the same as in F 1? both of which facts indicate 
that number of nodes is not appreciably affected by heterozygosis. 
As in all the other quantitative characters studied, the F 2 genera- 
tion exhibited a wide range of variation and the several F 3 
families had very different mean numbers of nodes, including 
types approaching those of the parents and also various inter- 
mediate types. 
A study of internode lengths explains the excess in height 
of F x plants over the average of the parent heights. Tho number 
of nodes in F x is apparently always distinctly intermediate be- 
tween the parent numbers, the internode length is so greatly 
increased by heterozygosis that F. plants are often nearly as tall 
as the tall parent, and always taller than the average of the 
parent heights — the former when the tall and short parents differ 
little and the latter when they differ much in number of nodes. 
In the two crosses in which internode length was calculated, the 
Fj plants had internodes longer than those of the long-internode 
parent. Tn Tom Thumb X Missouri dent, in fact, the latter 
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