84 
Research Bulletin No. 2 
The parent lots grown in 1911 had, in general, without re 
spect to earliness, shorter internodes than their progenitors of 
1910. This is doubtless due to the fact that the parent stocks had 
been selfed until they had lost much of the vigor acquired thru 
their former heterozygous condition. 
The F £ families of 1911 are not readily brought into line with 
the behavior of the F 3 families of the same year. Since they 
came from different F x plants from the F 2 family of 1910 and, 
therefore, from the F 3 families of 1911, and since these different 
F x plants may have had different internode-length inheritances 
from the more or less heterozygous parent stocks, it is not 
strange that their internode length should differ from the F 2 
family of the preceding year. 
The cross of Missouri dent with California pop (Table 31) 
gave F x progeny with somewhat longer internodes than even the 
tallest parent had, but the excess was not so great as in case 
of the cross of Missouri dent and Tom Thumb. In 1910 the 
mean internode length of ¥ 1 was about 8 mm. greater than that 
of Missouri dent, 40 mm. greater than that of California pop, and 
therefore 24 mm. greater than the average of the internode 
lengths of the parents. Similarly, in 1911 the F x families had 
internodes nearly 8 mm. longer than Missouri dent, nearly 38 
mm. longer than California pop, and about 23 mm. longer than 
the average of the parents. That the long internodes of F t are 
not due to dominance of long over short internodes but rather 
to increased vigor of growth due to crossing is indicated by the 
fact that the internode lengths of the F 2 families grown in 1911 
were only about 18 mm. greater than those of California pop, 
about 12 mm. less than those of Missouri dent, and therefore 
only about 3 mm. greater than the average internode lengths of 
the parents. Further, if dominance were concerned, the F 2 fre- 
quency distributions would be noticeably skewed. 
While no F 2 family had quite the combined range of the two 
parents, the lower extreme of the parents, as grown in 1911, was 
reached by three F 2 lots and the upper extreme by two. The 
variation in F 2 was considerably greater than in F x . There is, 
therefore, evidence of segregation of internode lengths in F 2 of 
this cross, as well as in the cross of Missouri dent and Tom 
Thumb; and here, moveover, the weather must have affected all 
generations practically alike since they all had about the same 
season of growth. 
