BULLETIN 629, U. S. DEPARTMENT OF AGRICULTURE. 
them on the previously moistened leaf to be inoculated. When all 
leaves in a pot were inoculated they were sprayed at once with an 
atomizer and placed in the moist chamber shown in figure 1, where 
they were allowed to remain 48 hours. These moist chambers, which 
will hold about forty 4-inch pots, cost less than $10 for four. Xo 
trouble was experienced from the leaves burning or turning yellow, 
and almost 100 per cent of the inoculations were successful. 
Inoculations of older plants were made in the order of heading 
of the varieties, beginning on April 10 and continuing to May 9, 
1916. There were 12 to 18 plants in each series. The stem-rust 
spores were always placed 
on the sheath inclosing the 
emerging panicle, while 
the inoculations with 
crown rust were made on 
the uppermost leaf blade. 
As with the seedlings, the 
inoculated plants were 
sprayed with an atomizer 
to insure the presence of a 
film of water and then 
kept in the moist chamber 
for two days. A special 
large glass-topped galvan- 
ized-iron moist chamber 
was made, holding eight- 
een 5-inch pots and allow- 
ing the tallest plants to re- 
main upright (fig. 2). 
The incubation period 
for the two rusts was ap- 
proximately the same. 
Generally, though not al- 
ways, the uredinia of the 
stem rust appeared first. Cool temperatures seemed to lengthen the 
incubation period, for during November the house was cooler than 
during the succeeding months and the uredinia during this time were 
noticeably slower in appearing. Other factors, such as light, also 
may have affected the results. 
Xotes on the appearance of flecks usually were made in 7 to 9 cla} 7 s, <j 
and those on the formation of uredinia after a period of not longer 
than 12 days. Further notes usually were taken on the quantity and 
character of infection. Xo counts of uredinia were made ; nor should 
too much emphasis be placed on whether or not all the leaves inocu- 
lated were equally infected, for it is obviously impossible to be cer- 
Fig. 
ass-topped galvanized-iron moist cham- 
ber used for mature plants. 
