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florescence pushes out from the enclosing sheath the spores are 
scattered by the wind over the oat field and finally the plant ap- 
pears with only the bare axis of an inflorescence with the frag- 
ments of glumes and other parts still attached. The inoculation 
of a healthy oat plant usually takes place at the flowering 
period. Some of the spores which are widely distributed over the 
field adhere to the developing kernels. Plants may become inocu- 
lated in threshing operations and in the subsequent handling of the 
grain and seedling infection seems to be the rule. 
The covered smut has a life history similar to that of the loose 
smut. Infection takes place in the seedling stage and the spores 
are developed in the floral region of the host. It also causes a 
more or less complete destruction of the kernel Gig. 3), The 
glumes, however, are less involved. They remain more or less 
persistent and conceal the smut spore masses. ‘The bases of the 
glumes are, however, more or less attacked and the tissues appear 
blackish due to the presence of the fungous spores among the host 
cells. The spores are distributed on the sound grain very largely 
in threshing operations. The two smuts accordingly differ in the 
time at which the contamination of the sound grain takes place. 
These two smuts are more or less coextensive with the cultiva- 
tion of oats. On an average probably 5 per cent. of the oat crop 
of the United States is destroyed by them. 
Lhe Loose and Covered Smuts of Barley.—There are two dis- 
tinct smuts of barley—the covered smut caused by Ustilago hordei 
and the loose smut caused by U. nuda. So fat as life histories 
are concerned, the covered smut is very similar to the covered smut 
of oats. Seedling infection occurs from spores which contaminate 
the seed in harvesting, threshing, and drilling operations. The 
loose smut, like the corresponding disease of wheat, develops from 
dormant mycelium in the ripe seed which arose from an infection 
taking place in the flowering period of the host. Both are fairly 
common in barley. The covered smut is particularly severe in the 
winter barleys which are grown in Virginia, Tennessee, and other 
parts of the South (Fig. 4). 
Stem Smut of Rye-—The fungus which causes this disease is 
very similar to the one which produces the flag smut of wheat. 
