454 
Journal of Agricultural Research voi. xxiii, No 6 
According to Arthur (i) farmers reported a bunt outbreak in 1859 in 
the Haw Patch district of Indiana that took half the crop. Although 
such epidemics are not common in Indiana, another one occurred in 
this same district in 1887 and in some fields caused an almost total loss. 
In total harm done in reducing the world's wheat crop, bunt is second 
only to rust (19). In the wheat section of the Pacific coast in America 
in 1919 it is estimated that between two and three million bushels 
were lost on account of it. Besides the actual reduction in yield, the 
spores clinging to the grain and straw may be harmful to certain animals, 
and added expense is required to clean the grain for flour if the crop is 
even slightly contaminated. It is known and dreaded in all countries 
where wheat is grown. The countless spores in the separator during 
thrashing are sometimes exploded by the static electricity of the revolv¬ 
ing cylinder and a fire is started that destroys both machinery and crop 
(PI. 1, A). During thrashing the liberated spores are disseminated by 
the wind, and, as Heald and George (16) have shown, distributed at the 
rate of more than 35,000 spores to the square inch during a single season 
over distant fields about to be planted to fall wheat. Under such condi¬ 
tions seed treatment will not prevent a smutty crop of winter wheat 
the following year if the season is favorable for infection by the wind- 
borne spores. Experiments have shown that in a few weeks after the 
first rains, however, the spores germinate, and in the absence of wheat 
seedlings to infect, the fungus dies within a month or 6 weeks. Spores 
have been kept in the dry for 12 years which would still germinate 
(Woolman and Humphrey. 3 ) 
McAlpine (28 1 29) describes the spores of Tilletia tritici (Bjerk.) Wint. 
as globose with reticulate roughened surface 15 to 22 y. (average \6}x) in 
diameter. Under suitable temperature and moisture conditions the 
resting spores germinate in air or water. In water a long septate, un¬ 
branched myedium is produced, whereas in air a short, septate, pro¬ 
mycelium is produced, at the end of which are borne 3 to 10 filamentous 
or sickle-shaped conidia. These conidia, fusing in pairs, produce the 
infection threads by means of which the parasite enters the host. This 
is accomplished between germination and the beginning of photosyn¬ 
thesis of the young wheat plant. Once established, the fungus grows 
until fruiting time, keeping pace with the growing point without serious 
injury to the host. It then produces a mass of hyphae in the walls of 
the young ovules, which results in such a quantity of odoriferous spores 
as to fill the ovaries to the point of bursting—that is, making “smut 
balls" about the size of wheat kernels. 
The resting spores are never produced except in the ovaries of the 
host. The parasite remains in a vegetative condition during the life¬ 
time of the host—whether it be 2 months or 10. The physico-chemical 
changes that take place in the wheat plant as it approaches maturity 
stimulate the bunt organism to similar changes, for it quickly spreads 
its hyphae through the remains of the nucellus and deposits masses of 
its own fruiting spores in the space normally occupied by the endosperm 
and embryo of the wheat. 
Bunt, in common with other smuts, apparently consists of but a single 
biologic race. Like other disease-producing organisms, it is selective 
for certain tissues (24). The nodes and growing points of the host are the 
8 Woolman, Horace M., and Humphrey, Harry B. Studies in the physiology and control or 
bunt or STINKING smut OR WHEAT. U. S. Dept. Agr. Bui. (In press.) 
