GNOMONIA 



20I 



phore, 14-20 Xi-i "5 /*. Perithecia of ascigerous form 

 with an ostiolum or beak projecting beyond surface of leaf; 

 asci 8-spored; spores hyaline, narrowly ovate, i-septate 

 below the middle, 16-18 X 5-6 //. 



Collecting and burning all the hanging leaves during winter 

 is the only practical method of stamping out the disease. 

 This practice, however, should be general in an infected 

 district, otherwise it is of little avail, as the spores are blown 



FlG. 55. Gnomonia erythrostoma. I, conceptacles 

 containing spermatia bursting through the epidermis 

 of a leaf; 2, spermatia; 3, section of perithecium of 

 ascospore stage ; 4, ascus containing spores ; 5, free 

 spores. All mag. 



from one orchard to another. Frank records an instance in 

 Prussia where the cherry industry was completely wrecked by 

 this disease, but after two years' work in collecting and burn- 

 ing all infected leaves, the epidemic was thoroughly stamped 

 out, and a return to the former productiveness followed. 



Wild cherries growing in woods and the bird cherry {Priau/s 

 avium) are also attacked by this disease, and may prove a 

 source of infection unless attended to. 



Plane leaf scorch. This is a very destructive disease, 

 attacked trees being often completely defoliated before the 

 end of July. The injury usually appears about the time when 



