154 



PLANT DISEASES 



The ascospores produced in the spring germinate and 

 penetrate the young shoots and leaves of the cowberry, 

 producing the brown spots previously alluded to, from the 



y 



f 





Fig. 33. Sclei'otinia urnula. i, conidial condi- 

 tion in young stage, x 250 ; 2, conidial form of fruit ; 

 at maturity, the narrow portions, or disjunctors, 

 deliquesce, and set the conidia at liberty, X25o ; 

 3, ascospores springing from mummified fruits 

 filled with sclerotia, X3 ; 4, ascus containing eight 

 spores, x 250 ; 5, paraphyses, x 250 (after Woronin). 



surface of which the summer or conidial form of fruit is 

 produced in less than three weeks. 



The following species of Sderotinia also form sclerotia 

 in the fruit of different species of Vacrinium : 



Sderotinia oxycocd, Wor., on Vaccinium oxycoccos. 



Sderotinia baccarum, Schroter, on Vaccinium myrtillus. 



