1038 
Journal of Agricultural Research 
Vol. V, No, 22 
Infection, both artificial and natural, occurs best on mature leaves, 
and this is associated with the movement of the stomata. 
Penetration of the leaf by the conidial germ tubes of C. beticola has 
been observed to occur only through open stomata, and consequently 
infection probably takes place during the day hours. An isolation of 
the invading organism is attempted by the leaf cells as soon as penetra¬ 
tion occurs, but when this is not successful, the fungus by further growth 
produces a well-defined leafspot. 
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