HERITABLE CHARACTERS OF MAIZE 
Ill. BRACHYTIC CULMS 
J. H. Kempton 
Bureau of Plant Industry, Washington, D. C. 
HIS variation consists of a short- 
ening of the internodes on the 
main culm and lateral branches 
without a corresponding reduc- 
tion in number or in the number and 
size of other organs. It arose in 1917 in 
the second generation of the Chinese- 
Algerian hybrid designated Dh416'. 
This second generation was _ being 
grown from self-pollinated seeds. | Ap- 
proximately one-quarter of the plants 
were brachytic, the actual number 
being five brachytic and twenty-one 
normal. One of the five brachytic 
plants was self-pollinated, and the re- 
sulting progeny were all brachytic. The 
progeny of a normal sister plant were 
all of normal stature. Statistical data 
secured for several characters in both 
the normal and brachytic progenies 
are given in Table I. It will be seen 
from the table that the brachytic strain 
exceeds the normal in the diameter of 
the culm and the total number of nodes, 
while the size of the leaves is about 
the same. The upper ear is somewhat 
smaller in length, but this is apparently 
compensated for by the additional ears 
as the total ear length is approximately 
the same in the two strains. 
Eleven hand-pollinated ears were ob- 
tained from the brachytic plants that 
were the result either of self-pollina- 
tions or crosses between sister plants. 
The progenies of these eleven ears with- 
out exception produced nothing but 
brachytic plants. These plants differed 
only superficially in their general 
dimensions from the parental brachytic 
progeny, their mean height being 8.8 
decimeters. When crossed with plants 
of normal stature the first generation is 
as tall or taller than the normal parent, 
and in the second generation both nor- 
mal and brachytic plants were secured 
in the familiar 3 to 1 Mendelain propor- 
tion. 
Brachytic variations are found in 
many agricultural species, as, for ex- 
ample, the “bush” varieties of peas, 
beans, squashes and tomatoes, and are 
popularly known as dwarfs. Cook? 
has pointed out a distinction between 
dwarfs which have suffered a reduc- 
tion in the size and number of many 
organs and those in which stature only 
is reduced. The designation brachytic 
has been suggested for the type where 
the internodes have failed to elongate. 
Dwarfing involving brachysm and 
also true dwarfing or nanism is a varia- 
tion which recurs in maize in widely 
divergent and wholly independent 
stocks. The instances, however, where 
brachysm alone is involved are not 
numerous. Hartley* apparently pos- 
sessed a true breeding brachytic strain, 
although it would seem that the leaves 
were somewhat shorter and broader than 
those of normal plants and Gernert! 
describes a single brachytic plant. 
‘Kempton, J. H., “Inheritance of Spotted Aleurone Color in Hybrids of Chine-e Maize.” 
Genetics, Vol. 4. May, 1919. 
* Cook, O. F., “Brachysm—A Heredity Deformity of Cotton and Other Plants.” liarpe 
of Research, Vol. 3, No. 5, February 15, 1915. 
‘Hartley, C. P., “Improvement of Corn by Seed Selection.” 
Agric., 1912. 
Year-book, U. S. Dept. 
*Gernert, W. B.. “The Analysis of Characters in Corn and their Behavior in Transmis- 
sion.” Champaign, IIL, 1912. 
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