126 
N. C. AGRICULTURAL EXPERIMENT STATION. 
ten was placed sterile soil, upon the second ten sterile soil with asco¬ 
spores upon the soil. At the edges of ten other leaves small pieces of 
manure were placed with ascospores on the edges of the manure which 
were farthest away from the lettuce leaf. 
There was no infection in either the first or second case through 
soil while in the third case the spores germinated, grew over the ma¬ 
nure and speedily caused the disease upon each of the ten leaves. 
It appears from this and other experiments previously quoted that 
ascospores are not capable of direct infection of the lettuce plant but 
E 
that the germ tubes formed from the ascospores must acquire a con¬ 
siderable strength and develop a vigorous mycelium by a saprophytic 
habit before they can bring about infection of healthy tissue. Even 
the nutriment present in ordinary rich soil will not give the mycelium 
vigor sufficient to produce infection. 
lo fully demonstrate the parasitism of the ordinary vigorous myce¬ 
lium the following test was made: On December 30, 1907, ninety-six 
plants in outdoor beds were inoculated at various places with masses of 
