264 
Journal o f Agricultural Research 
Vol. XXIX, No. 6 
heads germinated and formed mycel¬ 
ium but no conidia. Conidia were pro¬ 
duced by the form previously used. 
He called the form from Japan Ustil¬ 
ago hordei. This was evidently the 
form which is now known as U. nuda 
which causes loose-smut. Brefeld evi¬ 
dently made his infection studies with 
the fungus of covered smut, Ustilago 
hordei. He makes no mention in this 
paper of further infection studies after 
discovering this difference in the barley 
smut fungi. 
In 1899 Kellerman and Swingle {14), 
in a study of the barley smuts, des¬ 
cribed the two species U. hordei (Pers.) 
Kell, and Sw., covered smut, and U. 
nuda (Jens.) Kell, and Sw., loose-smut. 
They cited Jensen’s statements con¬ 
cerning floral infection but said, ‘‘This 
view requires confirmation.” 
Maddox {16) concluded from care¬ 
fully conducted experiments that the 
loose smuts of wheat and barley could 
not be produced by smutting the seed 
or by mixing spores with the soil. He 
says: 
Artificially smutted is putting the smut germs on 
the ovary about the time the pollen is ripe, which 
will always reproduce the disease the following 
year. 
According to Hori {11), K. Yamada 
in 1896 and S. Nakagawa in 1897 pro¬ 
duced loose-smut in wheat by inoculat¬ 
ing the flowers with mature spores of 
Ustilago tritici. 
Brefeld {2) in 1903 discussed methods 
of floral inoculation of wheat and bar¬ 
ley with the loose-smut spores. He con¬ 
cluded that infection takes place through 
the flower. Again in 1905 Brefeld {3) 
published, in detail, methods used in 
attempting to infect barley with Ustilago 
nuda by inoculating the flowers and* 
seed with spores and by inoculating the 
young seedlings with germinated spores. 
In one experiment he obtained 1 per 
cent infection where the seedlings were 
inoculated with germinating spores, 
while two-rowed barley treated simi¬ 
larly remained smut free, as did the 
control. This was the only indication 
of seedling infection. Brefeld’s results 
led him to conclude, however, that— 
infection in the blossom is the predominant form of 
infection of the host plants, if not the only one. 
Hecke {8) produced floral infection in 
barley in 1904, and in 1905 he {9) figures 
the mycelium in the scutellum of bar¬ 
ley. He adheres to Brefeld’s termi¬ 
nology and calls the loose-smut fungus 
Ustilago hordei. 
Hori {11) in 1907 states that he ob¬ 
tained floral infection by Ustilago tritici 
and U. nuda as early as 1900. After 
discussing the findings of Brefeld and 
Hecke he makes the following state¬ 
ment: 
Hence it is now clear that at least U. tritici, U- 
nvda and V. hordei ma v naturally infest the respec¬ 
tive host plants by the flower infection. 
Hori evidently was referring to the 
loose-smut of barley both as U. nuda 
and U. hordei. Brefeld {1) called the 
loose-smut fungus U. hordei when he 
first discovered that there were two 
barley smuts. Hori was probably con¬ 
fused by this difference in nomencla¬ 
ture. 
Falck {5) in 1908 and Lang {15) in 
the following year studied the infection 
of wheat by Ustilago tritici cytologically 
and showed the mycelium in the stigma 
and the young ovaries and showed it 
ramifying in the cells of the embryo at' 
various stages of development. 
Freeman and Johnson (7) in 1909 
studied the loose smuts of wheat and 
barley. They inoculated the flowers at 
different stages of maturity and found 
that infection takes place from the 
time when the stamens are still green to 
the time when the ovary is one-third its 
mature size. They found the opti¬ 
mum time for infection to be when the 
flower is in full bloom or when the 
ovary is just commencing to develop 
after fertilization. 
Brioli (4) in 1910 studied floral infec¬ 
tion in wheat and barley and confirmed 
the work of previous investigators. 
He illustrates the mycelium in the scu¬ 
tellum of wheat and says that he found 
mycelium in the scutellum of one 
variety of barley but not in the other 
varieties: 
Nur bei Kornern der Niederbayerischen Gerste 
habe ich My cel gefunden. Bei den anderen 
Gerstcn nicht. 
He attributes the lack of mycelium in 
the kernels to resistance of the host. 
PRESENT INVESTIGATIONS 
SEEDLING INFECTION 
For many years after the discovery 
of the hot-water seed treatment by 
Jensen {12) this method was recom¬ 
mended as being the only treatment that 
would control the loose-smuts of wheat 
and barley. In 1914, Johnson {13) 
reported the control of loose-smut of 
barley by treating the seed with forma¬ 
lin. Tisdale, Taylor, and Griffiths 
{21) in 1923, obtained satisfactory 
control of loose-smut of barley by 
treating the seed with formaldehyde 
and with chlorophol, an organic mer¬ 
cury compound. Six varieties of barley 
were included in this experiment. 
Since that time Semesan, Corona 620, 
