FROMME: THE CULTURE OF CEREAL RUSTS 815 
where the temperature ranges between 20° and 30°.* The 
temperature here was quite constant for each twenty-four hours 
throughout the experiment. It did not fall below 25° from 10 
A.M. to 5 P.M. nor rise above 20° from midnight to 6 A.M. 
The other culture was placed in the greenhouse where the tem- 
perature fluctuation was between 14.5° and 21°. Here the tem- 
perature remained quite constant at 16° for the greater part of the 
twenty-four hours. It reached 21° for a short period at noon and 
14.5° at midnight. Both cultures were covered after inoculation. 
The first visible signs of infection became apparent on the culture 
in the ‘‘stove’’ on the fourth day after inoculation and fully ripe 
pustules were produced on the seventh day. Evidences of infection 
did not become visible on the culture in the greenhouse until the 
seventh day after inoculation, which was the date of sporulation 
for the culture in the ‘‘stove,” and ripe pustules were not formed 
until the twelfth day. The high temperature of the ‘‘stove,”’ 
which was an average increase of about 7-8°, was apparently 
responsible for a marked increase in the rate of development of 
the fungus and a decrease of five days in the incubation period. 
No differences in the degree of infection secured on the two cultures 
were apparent. The experiment was repeated immediately, but 
without a control, and the incubation period for this culture in the 
“stove” was but six days. This is the shortest incubation period 
I have observed. 
Further cultures gave results as follows. No.’7 in the ‘‘stove,’’ 
incubation period seven days. The temperature for each day 
was 20° from 6 P.M. to 6 A.M. and 25-30° from 8 A.M. to 2 P.M. 
Three controls in the greenhouse, incubation period nine days. 
Temperature 10-15.5° from 6 P.M. to 6 A.M. and 15.5-21° from 
9 A.M. to 5 P.M. No. 8 in the ‘‘stove,’’ incubation period nine 
days. There were many minor fluctuations in this period. The 
maximum was 30°, the minimum 8°. The general range was 
distinctly lower than in the preceding test. Two controls in the 
greenhouse, incubation period twelve days. Temperature 10- 
15.5° from 6 P.M. to 6 A.M. and 15.5-21° from 10 A.M. to 3 P.M. 
* The temperature records were obtained with Richard Fréres’ self-recording 
thermometers. 
