56 



James G. Horsfall 



Figure 11. 



A TYPICAL SINGLE SPORE CULTURE OF CERCOSPORA ZEBRINA ON 15 

 CENTIMETERS OF OAT AGAR 



Life history. All the evidence points to seed distribution of the fungus. 

 The author repeatedly has found infections in the greenhouse on primary 

 leaves of alsike and white clover. When seeds from the same lot that 

 produced these infected plants were examined, the superficial mycelium of 

 the fungus, as found by Hopkins (1921) on bur-clover seed, was seen. 



Wolf (1916) found conidia in centrifuged washings from seed. Whether 

 these or the seed-borne mycelium or both initiate the primary cycles is 



