Nebraska Experiment Station Research Bulletin 22 
was removed together with the cans, a false bottom made of slats 
placed in the tank about 12 inches below the top, and water 
brought up to within % or % of an inch of this false bottom. By 
means of a heater with a thermostat connection, the water could 
be brought to the temperature desired. Over the top of the 
tank, a large pane of glass was closely fitted. Owing to the large 
volume of water present, these modified tanks served most ad- 
mirably for incubation chambers, both from the standpoint of a 
uniform temperature and from that of the production of a 
heavy film of water on the leaves. A tank thus fitted up held in 
the neighborhood of 75 S^-inch pots. 
PROCEDURE 
On February 1, 1922, about 2,000 Little Club (C. 1. No. 
4066 from Moccasin, Montana, 1921) wheat seedlings, seven days 
old, were inoculated with two weeks old material of Puccinia 
graminis tritici Form III, a stock culture of which was kindly 
furnished the writer by Dr. E. C. Stakman of the Minnesota 
Agricultural Experiment Station in the fall of 1921. During the 
season it was transferred each week to Little Club wheat. It 
may be stated further that it was the only strain of rust intro- 
duced into the greenhouse during the season of 1921-1922. 
As usual in rust inoculation of wheat seedlings, the plants 
were trimmed before inoculation and five such trimmed plants 
were retained in each pot. The plants were sprayed with water 
by means of an atomizer before inoculation and the wet fingers 
drawn over leaves just prior to inoculation. 
A composite inoculum was obtained by shaking the spores 
from the pustules on to a glass plate. While the waste of rust 
material is rather large by this method, it is counterbalanced 
by the more uniform and higher percentage of successful infec- 
tions obtained. As Form 111 was the only rust material present in 
the greenhouse, no necessity for the sterlization of the fiat needle 
after each inoculation existed. Coupled with the fact that it was 
not necessary to stop and obtain spores from the pustules on the 
leaves with the needle at each operation, this greatly facilitated 
the work. Thus, with an assistant to get the plants ready and 
place the inoculated plants in the incubation chambers, the 
writer could inoculate from 2,000 to 2,500 plants in six to eight 
hours. 
The inoculated plants were incubated for 48 hours in the 
incubation chambers, which were maintained at a constant tern- 
