124 
N. C. AGRICULTURAL EXPERIMENT STATION. 
The checks were exact parallels of the inoculations but without spores. 
The results of these inoculations are shown in the following table: 
TABLE XII.—REGARDING INFECTION BY ASCOSPORES. 
Number of Leaves 
Inoculated 
Methods of Inoculation 
% 
Surface of Leaf 
Inoculated 
Number of Leaves 
Infected in 7 Days 
10 
Ascospores in lettuce broth_ - - - - 
Upper 
6 
10 
Ascospores in lettuce broth_ .. - 
Lower 
0 
10 
Ascospores in water on bruised spot of leaf _ 
Both 
5 
10 
Check_ _ 
Upper 
0 
10 
Check._ _ - _ 
Lower 
0 
10 
Ascospores in water_ - - . .. 
Upper 
0 
10 
Ascospores in water_ - -- 
Lower 
0 
5 
Ascospores at needle-prick.. .. 
Upper 
0 
5 
Ascospores at needle-prick. . ._ _ 
Lower 
0 
It is noted that the only infections occurred in the presence of the 
nutrient lettuce broth or at the bruised spots where, virtually, broth ex¬ 
isted. This lack of ability of the spores alone, or in water merely, to. 
infect was of such importance that repeated tests of this point were 
made. 
Thus on November 21, 1907, ten lettuce leaves were inoculated upon 
the upper surface with ascospores in sterile water and on December 3, 
1907, there was still no sign of infection. 
On November 21, 1907, fifteen lettuce leaves were inoculated upon 
the lower surface with ascospores in sterile water and on December 3, 
1907, there was still no sign of infection. 
In both of these cases the leaves, kept in a damp chamber in ordinary 
room temperature, were fresh and healthy at the end of the experiment, 
even at the marked spots where the spores were placed. On December 4, 
1907, spores were washed from the leaves which had been inoculated 
but which had shown no infection. Upon microscopic examination in 
all cases where the spores were found it was seen that they had germ¬ 
inated in a normal way but with no branching of the mycelium or 
flattening of its end. It was thus made clear that the lack of infection 
was not due to non-viability of the spores. 
On December 4, 1907, sixteen lettuce leaves were inoculated in a damp 
chamber with spores placed in lettuce broth together with small pieces of 
lettuce leaf; of these, nine leaves became diseased in seven days while 
seven showed no infection. At the same time sixteen more leaves were 
prepared in the same way except that sterile water was used in place 
of the lettuce broth. In this case none of the leaves showed infection 
