ASCOMYCETES 



179 



the new growth. It was formerly supposed that this fungus was 

 very largely propagated by a perennating mycelium, or by infec- 

 tions resulting during the summer and persisting in the woody 

 parts until the following season, but as will be shown later, infec- 

 tions must generally occur as the buds unfold. The percentage 

 resulting from a mycelium remaining alive in the hypertrophied 

 twigs is very small. The badly affected twig dies and the my- 

 celium with it. From other affected twigs diseased leaf buds are 

 seldom produced (Fig. 65). 



FIG. 65. ONE HEALTHY AND THREE DISEASED TWIGS OF PEACH; THE 

 CENTER TWIGS RECOVERED FROM THE ATTACK 



Susceptibility of host varieties. There is a great difference in 

 the susceptibility of different varieties under similar conditions. 

 Moreover, a single variety may show a difference in resistance 

 when grown under diverse environmental conditions. A list of 

 the most susceptible varieties in New York would not correspond 

 with a list for California. Among susceptible varieties in the far 

 West have been included such as the following : Crawford's 

 Early and Late, Elberta and Salway, Heath King and Kale's 

 Early, Lovell, Old Mixofi Free, etc. ; while for Ohio, Mountain 

 Rose, Old Mixon, Globe, Elberta, and others are among those 

 most affected. 



