SORGHUM SMUTS AND VARIETAL RESISTANCE 13 
Experiment Farm, Rossryn, Va., in 1919 and 1920, and at the Brook- 
lyn Botanic Garden, Brooklyn, N. Y., in 1921. 
METHODS EMPLOYED IN THE VARIETAL STUDIES 
In the first experiments at Columbia, Mo., in 1915 (95), seed of 22 
varieties of sorghums, including sorgos, broomcorns, kaoliangs, 
kafirs, durras, and milos, were inoculated with spores collected the 
previous autumn from kafir grown in the vicinity of Columbia. 
Four varieties, feterita, Dwarf Yellow milo, Standard Yellow milo, 
and a durra, remained free from infection. The other varieties had 
a percentage of infection ranging from less than 1 to more than 31 
per cent. The studies at Columbia {96, 98) were continued in 1916, 
1917, and 1918, an additional number of varieties being used each 
season. 
The seed of the varieties of sorghum grown at Columbia was 
obtained from a number of sources, for the most part from seedsmen, 
but also from the agricultural experiment stations of Missouri, Louis- 
iana, Kansas, Oklahoma, and Texas. The orginal seed of many of 
these varieties was also used at the Arlington Experiment Farm, 
Kosslyn, Va., in 1919 and 1920 and at the Brooklyn Botanic Garden 
in 1921. In addition, a large number of varieties was obtained from 
B. E. Rothgeb, of the Office of Cereal Investigations, and H. N. Vinall, 
of the Office of Forage- Crop Investigations, Bureau of Plant Indus- 
try, and used in the seedings at Rosslyn and Brooklyn. Many of 
the original samples of seed were used in two or more seasons, no 
attempt being made to collect seed from one crop for use during the 
next year. 
The seed received from the various seedsmen was listed under 
various names. These varieties were all carefully examined and 
compared with authentic material. Dr. C. R. Ball and B. E. Roth- 
geb, of the Office of Cereal Investigations, and H. N. Vinall, of the 
Office of Forage- Crop Investigations, have rendered valuable assist- 
ance in the identification of the collections. 
In several cases the seed samples contained mixtures of varieties. 
This was especially true of the sorgos. So far as possible, however, 
the rows were carefully rogued before the counts were made. Fail- 
ure to rogue completely may account for the occasional appearance 
of smut in certain varieties which otherwise have been free from smut. 
As previously stated, the spores first used for inoculation were 
collected in the fall of 1914 from kafir growing in the vicinity of 
Columbia, Mo. In subsequent years smutted heads were taken 
from some of the varieties in the experimental plat, and these furnished 
a supply of spores for inoculation. Spore germinations were always 
made to determine their viability. 
From 100 to 200 seeds of the different varieties were placed in 
packets, inoculated by dusting heavily with the spores, and then 
sown as soon as possible. Usually an uninoculated series of the 
varieties was sown also as a check. Very little smut appeared in the 
uninoculated rows, indicating that the original seed used was almost 
entirely free from smut contamination. 
The rows usually were 40 inches apart. The length of row varied, 
but an attempt was made to have at least 100 plants at maturity. 
