20 BULLETIN 1383, U. S. DEPARTMENT OF AGRICULTURE 
avoid mixing different lots and varieties. This would require a drier 
of special construction, entail a large amount of work, and probably 
add so much to the cost of treatment as to make it unprofitable. It 
has been suggested, however, that the commercial grain drier might 
be employed advantageously both to treat and to dry wheat in quan- 
tities large enough to supply clean seed for an entire community. A 
system of this kind would greatly facilitate the establishment of smut- 
free areas. It has been the experience in the State of Indiana, 
according to Gregory (o), that the establishment of such areas "will 
greatly reduce the dangers of the spread of the smut," and it appears 
that wheat thus can be maintained free from loose smut for several 
vears. 
PREVIOUS INVESTIGATIONS 
The use of grain driers and other kinds of drying apparatus in 
controlling loose smut of wheat and barley, or both, has been reported 
by a number of workers. A comprehensive review is given by Appel 
and Riehm (/). Later Lind (10) conducted experiments along this 
line. In general, the seed was previously soaked for varying periods 
or soaked and left to stand wet for periods of different length. The 
grain then was subjected to currents of dry hot air at temperatures 
high enough to control the parasite and to dry or partially dry the 
seed. Satisfactory results followed in some cases, particularly when 
special laboratory apparatus was used. Serious difficulties arise in 
attempting to standardize such treatments, however, because the 
hot dry air passing around soaked grain causes rapid evaporation 
and with it wide variation in temperature. Obviously the successful 
application of a thermal treatment involving large quantities of seed 
grain precludes a positive control of temperature. A saturated 
recirculating atmosphere was therefore employed in the following 
experiments to eliminate evaporation and its attending difficulties. 
By this means it was possible to maintain temperatures with a plus 
or minus variation not in excess of 0.2° C. 
METHODS AND MATERIALS 
There are two types of grain driers in general use, upright and 
rotary. In both types there are many different designs. In the 
rotary type drying is effected by currents of hot air as the grain 
slowly passes through a revolving cylinder, and in the upright type 
as the grain slowly flows through channels from the top to the 
bottom of the drier. An upright drier was used in the experiments 
recorded here. (Fig. 4.) This machine, though smaller, was like the 
standard sizes. It had a capacity of 2 bushels of wheat and was 
provided with a return pipe, so that the air could be recirculated. 
This return pipe runs along the side opposite that shown in Figure 4. 
The air was forced through the channels containing the grain by a 
powerful motor-driven fan. A recording thermometer was used to 
regulate the temperature in the drier. Steam before entering the 
machine passed through a thermostatically controlled valve which 
was opened or closed by air pressure. The latter in turn was con- 
trolled by a sensitive bulb. The bulb was inserted in the machine 
about 30 inches in front of the steam outlet. It was found that the 
amount of steam necessary to raise the temperature to the desired 
degrees (46° to 49° C.) was more than ample to keep the recirculating 
air saturated. 
