268 
Journal of Agricultural Research 
Vol. XXIX, No. 6 
sible, the mycelium within the seed 
may not be responsible for the infection 
which takes place when the seed is sown. 
The fact that loose-smut is controlled 
by superficial disinfectants would indi¬ 
cate that it is not internal unless it be 
very superficial so that these fungicides 
destroy it. 
The results show that, to a large ex¬ 
tent, the hulls (glumes) are the limit¬ 
ing factor in the infection of barley by 
Usiilago nuda. However, with the ex¬ 
ception of Nakano Wase and Greece, 
comparatively high percentages of loose- 
smut were obtained by inoculating hulled 
seed, the lowest percentages of infected 
plants in the other four varieties being 
14.29 per cent in Alaska. This amount 
of infection is sufficient to account for 
the percentages of loose-smut in barley 
which generally occur in nature. As 
is true with the covered-smut fungus, 
U. hordei, the inoculation of hulled seed 
with U. nuda does not insure infection. 
The hulls evidently are an important in¬ 
hibitor. There may be different strains 
of the fungus, as Faris (6) has pointed 
out in the case of U. hordei, which infect 
certain varieties more readily. While 
there is a chance for the spores to enter 
between the glumes at flowering time 
when spore material is abundant, there 
seems to be an equally good or better 
chance for them to enter when the grain 
is being threshed and handled. The 
hulls often are broken and some kernels 
are completely dehulled in the threshing 
process. It is true that the loose-smut is 
largely dissipated by harvest time, but 
there no doubt is enough spore material 
left^on diseased heads and surrounding 
plants to cause the low percentages of in¬ 
fection which ordinarily occur in nature. 
If barley is inoculated naturally by U. 
nuda in the same way as it is by U. hordei 
the lower percentages of loose-smut 
which generally occur would harmonize 
with the fact that the spores disappear 
more readily in the case of loose-smut 
and that there is much less inoculum 
available at threshing time 
Nakano Wase remained smut-free in 
these experiments. It failed to be¬ 
come smutted with covered smut in 
the experiments of Tisdale (19). So 
far as the writers know, neither loose 
nor covered smut has been found in 
this variety in the field. 
SEEDLING INJURY 
In previous experiments it was no¬ 
ticed that in most cases the stands 
of seedlings from dehulled-inoculated 
seeds were poor as compared with the 
stands from dehulled and uninoculated 
seed. It even was necessary in some 
cases to reseed in order to get a satis¬ 
factory stand from inoculated seed. 
Many of the seedlings that emerged 
from inoculated seed were abnormal in 
appearance. Many of them emerged 
at an angle rather than normally. 
A set of experiments was planned 
for the purpose of making a study of 
the effects of the loose-smut fungus 
on the germination of the seed and 
the emergence of the seedlings of 
barley. Seed of two varieties, Texas 
Winter and Han River, from the 1921 
crop grown on Arlington Experiment 
Farm was dehulled. A part of the 
dehulled seed of each variety was in¬ 
oculated and sown and a part sown 
without inoculation. It was sown 
about 2 inches deep in soil on green¬ 
house benches at Arlington Experi¬ 
ment Farm, on January 29, 1924. 
Close observation every few days re¬ 
vealed a noticeable difference in the 
number of seedlings emerging from 
the inoculated and uninoculated seeds. 
Stands were much better from the 
latter. Texas Winter germinated very 
poorly in either case. After several 
days seeds which failed to produce 
plants were dug up. Many of the 
seeds of Texas Winter had decayed, 
due to the presence of other organ¬ 
isms. In Han River, however, where 
the uninoculated seed germinated well 
and produced a good stand of normal 
plants (PI. 2, A), the inoculated seeds 
were’ found to be germinated but the 
seedlings were developing very ab¬ 
normally (PI. 2, B). The coleoptiles 
often were much shortened, thick, and 
tough. For this reason, apparently, 
they failed to open normally at the 
tip and the plumule was held within, 
causing it to curl into various shapes 
which prevented emergence. Many 
seedlings which did emerge came 
through the soil at. .an angle instead 
EXPLANATORY LEGEND FOR PLATE 2 
Injury to seedlings of Han River barley by U&tilagio nuda. Seed dehulled and sown in soil on greenhouse 
bench. Jan. 29,1924. 
A. —Healthy seedlings from uninoculated seed; 93.44 per cent of the seed produced plants of this type, 
which were smut-free at maturity. 
B. —Seedlings from inoculated seed infected by TJ. nuda. Only 11.29 per cent of the seed produced seedlings 
sufficientl y normal to emerge. The remainder of the seeds germinated but the seedlings were too abnormal 
to emerge. The infected coleoptiles failed to open up normally and the seedlings became twisted in various 
ways. 
