14 BULLETIN" 925, U. S. DEPARTMENT OF AGRICULTURE. 
the area available for photosynthesis has been reduced somewhat. The 
degree of this reduction is yet to be determined, but with the ex- 
cejDtion of this reduction which, under certain conditions, may be 
beneficial, there should be no other physiological difficulties in com- 
bining high productivity with brachytic stature. 
Genetically, however, more difficulties are to be expected. Yield of 
grain, like most quantitative characters, is one of those relatively 
unstable characters difficult to recover from hybrids involving small- 
eared varieties. If only 10 factors are involved in maximum grain 
production, all 10 of these would be expected to occur in homozygous 
combination with brachytic culms in an F 2 hybrid only once in 
4,195,304 plants. To be reasonably certain of securing the combi- 
nation in an F 2 hybrid, at least 12,585,912 plants should be grown. 
It is, however, an unfortunate fact that probably many more than 
10 factors are involved. The form of the inflorescence alone can be 
resolved into several component parts, such as length, diameter, num- 
ber of seeds, size of seeds, number of rows, volume, and weight of 
seeds, all of which are known to be inherited separately, and even 
these subdivisions are far from being simple characters, 
With the several advantages, the commercial value of the bra- 
chytic variation depends upon the success with which the shortened 
internodes may be combined with the grain production of the stand- 
ard dent varieties. It is not unlikely that if such a combination were 
effected the value of the strain would be appreciated in areas out- 
side the regions of extreme climatic conditions. The brachytic char- 
acter is one which reappears in the perjugate generation of hybrids, 
and the possibility of combining the dwarf stature with the high pro- 
ductivity of commercial varieties will be considered. 
INHERITANCE OF BRACHYSM IN HYBRIDS WITH COMMERCIAL 
VARIETIES. 
BRACHYTIC X BOONE. 
In an effort to combine the brachytic character of the culm with 
the high productivity of commercial varieties, several crosses have 
been made. Two crosses were made with the Boone County T\ nite 
variety, and a few first-generation plants of each cross were grown 
in the greenhouse and self -poll mated. Three ears resulted, and a 
progeny of each of these, as well as a large population of the first 
generation, was grown in the field at Lanham, Md. The first-gen- 
eration plants grown in the field were fully as large as the Boone 
parent and remarkably uniform. A number of characters were 
measured, as shown in Table III. 
The three second-generation progenies segregated into normal 
and brachytic plants, with well-defined classes closely approximat- 
