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destructive disease in all the other wheat-growing regions of the 
world . 
Bunt of wheat is caused by two closely related species of smuts, 
illetia tritici and T. laevis. These two species are distinguished 
by the fact that the spores of Tilletia laevis are smooth and more 
or less irregular in shape. On the other hand, the spores of T. 
tritici have a wall with reticulate thickenings, so that the spores 
viewed in surface appear as a network. They are also nearly 
spherical in shape and much more uniform in size. 
Both species of bunt appear to have a similar life history. In 
each case the parasite gains entrance to the host plant in the seed- 
ling stage. Following penetration the fungus develops in the em- 
bryonic tissue of the host and growth becomes particularly vigorous 
in the developing ovary, so that the latter comes to be filled with 
the spores of the parasite. An infected plant can readily be recog- 
nized very soon after the heading of the grain. The heads appear 
somewhat greener and, since the infected kernel develops more 
rapidly than the normal, the glumes are pushed apart somewhat. 
The mature heads of diseased plants, since they are lighter, do not 
bend over or nod as is the case with the normal (iin T)% 
The spores remain enclosed in the surrounding tissues of the 
ovary and constitute what is known as the smut ball. Since the 
diseased plants are harvested with the sound ones, these smut balls 
are more or less broken when the grain is threshed and the spores 
become scattered over the sound grain from the normal plants. 
Many smut balls, however, may escape, but these may be broken 
in the subsequent handling of the grain. The spores, which are 
very small and exceedingly numerous, have a very distinct, dis- 
agreeable odor, which is responsible for the common name of 
stinking smut. The injury to the wheat lies not only in the actual 
destruction of grain, but also in the dockage of the badly contami- 
nated grain, which must be cleaned before grinding into flour. 
It is usually the spores which are in contact with the outside of 
the kernel that are responsible for the infection of the young seed- 
ling. They come in contact with the kernels in various operations 
attending harvesting, threshing, and drilling. A machine that has 
threshed smutted wheat becomes badly contaminated with these 
