10 
BULLETIN 925, U. S. DEPARTMENT OF AGRICULTURE. 
2U 
Q 10 30 50 70 90 J/O /go /so c/v 
Fig 
3. — Frequency distribution for the length of 
the third branch in an F 2 of Tom Thumb pop 
corn X Florida teosinte. 
character affected is the length of the ear stalk, which shows a reduc- 
tion in internode length similar to that of the main culm. While 
this may be considered simply as the general extension of the 
brachytic tendency to all the lateral branches, as indicated also by 
the condition of the suckers, it must be remembered that the brachytic 
nature of the ear stalk on plants of normal stature is not ordinarily 
reflected in the main culm. 
This further shortening of the ear stalk on brachytic plants indi- 
cates that the brachytic stalks of normal ears are the result of a 
genetic change separate from 
that which caused brachytic 
internodes on the main culm. 
Support for this latter con- 
tention is derived from a hy- 
brid between Florida teosinte 
and Tom Thumb pop corn 
(3). If the ear stalk is an 
example of brachysm similar to that of the main stalk, the second 
generation of the hybrid between teosinte and maize should give the 
same evidence of segregation of this character as is found with the 
internodes of the main culm when plants with brachytic culms are 
crossed with those of normal stature. 
With the second-generation plants, the third branch from the top 
on the main culm is assumed to be homologous with the ear stalk of 
normal maize, since it is borne at approximately the same node as 
the ear of maize. The frequency distribution for the length of this 
branch on second-generation plants of the Tom Thumb X Florida 
hybrid is shown in figure 3. 
It is apparent that there is no bimodality in the distribution of 
branch lengths, and it must be concluded that the brachysm of the 
ear stalk of normal maize does not behave as a simple Mendelian 
character in crosses with teosinte. 
Slight evidence for the discontinuous nature of the brachysm of 
ear stalks is to be found in the second generation of a cross between 
Boone County White and the brachytic strain. The frequency dis- 
tributions for the length of the ear stalk on brachytic plants directly 
descended from the original variation and on the first and second 
generation plants of the brachytic-Boone cross are shown in figure 
4. While the brachytic plants had shorter ear stalks than normal 
plants, the frequency distribution for this character on the normal 
segregates of the second generation of the hybrid suggests a bimodal- 
ity that is most easily explained by assuming an independent inheri- 
tance of the ear-stalk character. Too much confidence must not be 
placed in results of this sort, as it is obvious that at least one other 
is involved in the length of the 
factor besides length of internode 
