10(1 
Research Bulletin No. 2 
growth, and, second, that certain of the 1911 F 3 families were 
taller than their 1910 F 2 parents, tho they required less time 
to complete their growth. It would seem that sometimes, at least, 
the conditions that hasten development are favorable to a large 
height growth while the conditions that prolong growth unduly 
arc unfavorable to great height growth. Since the soil and 
weather conditions to which the Missouri dent and F 2 plants 
were subjected in 1010 were practically the same for both lots 
and since the same was true for the Missouri dent and F 3 
families in 1911, the markedly different behavior of the two lots 
in the two seasons was due obviously to an inherent difference 
between the two lots of plants — a difference in the way they 
responded to like environments. Whether this difference may 
have been as was suggested above, a matter of different optimum 
temperatures for the two lots, or whether the more nearly com- 
plete homozygosis of Missouri dent than of the other lots may 
have been a controlling factor, cannot now be said. It is easy 
to see that Missouri dent may have had shorter stalks in 1911 
than in 1910, notwithstanding the moister conditions of the 
latter season, because of repeated selling, and that it may have 
been later in 1911 than the year before because of the cooler 
weather. The 1911 F 3 families might then have had taller 
stalks than their 1910 parents because of the moister conditions 
in 1911. It certainly could not have been due to a greater degree 
of heterozygosity. But why were they earlier under the cooler 
conditions surrounding them in 1911 than were their F 2 parents 
under the hotter conditions of 1910, unless the optimum tempera- 
ture for them is lower than for Missouri dent? 
While there are, then, numerous difficulties to be met before 
a satisfactory explanation can be given of some of the facts 
brought out in this study of the inheritance of duration of 
growth, they should not be permitted to obscure the simple 
facts that a cross of a very early variety of corn with a very late 
variety produced an F 1 generation strictly intermediate between 
the parents in earliness, F 2 generations with a range of varia- 
tion from the early parent to, or nearly to, the late parent, and 
F 3 generations with diverse seasons of blossoming. From Table 
39 it can be seen that the latest F 3 family blossomed on the 
average a little over three weeks later than the earliest F 3 
family and that the earliest three F 3 families were all but out of 
Howe 1 ]* before the latest three began blossoming. The impression 
of distinct difference in earliness made by the plants in the field 
was even more vivid than that made by the figures in the table. 
The photograph reproduced in this paper (figure 21) gives some 
indication of the differences as they appeared in the field. 
There is one other feature of this study of time of blossoming 
