Notes upon Cei,ery. • 207 



side of the leaf; and the operative fungus was found, to be one 

 called Septoria Peiroselini, Var. Apii. The form on celery 

 is a disease which has been known to mycologists in this country 

 only about six years, and with favorable conditions for its spread, 

 it has proved to be a most destructive celery disease. In the gar- 

 den mentioned this fungus did not spread rapidly during the 



50. — Growth of the Cercospora in agar. 



summer, and it was not until early autumn that much harm 

 seemed to have resulted from its action. With a slight attack 

 the irregular spots are well defined ; but with conditions more 

 favorable for the disease the fungus may spread rapidly to the 

 whole surface of the leaflets (illustrated in Figure 51), and even 

 to the petioles, causing a complete wilting of affected leaves. 

 The minute, black, fruit bodies, or pycnidia, are then abundant on 



