Pr:Acii LicAK CuuL. 



283 



in the development and opening of the bud in the spring. This is proved 

 by the fact that spraying before the buds swell will prevent the disease, 

 while if the application is made after the tifjs of the leaves show, the 

 disease is seldom well controlled. 



Circumstantial evidence indicates that spores of the fungus are har- 

 bored through the winter most probably on or between the bud scales. 

 When the buds swell the tender leaves wathin are thus exposed and 

 if rains come at this time the spores probably germinate, sending forth 



(^hore 6c>or/hG 



^r/nimotarc shore 



'\ Sac 



myce/ii/m of^/iofu/iqas 

 c/row/nq //7 t/^e //'ssi/e 



Fio. 81. — Cross section of a diseased portion of a leaf, showing the fungus and 

 its relation to the leaf tissue. Highly magnified. 



a germ tube which penetrates the young leaves within, thus establish- 

 ing the fungus. Evidence of the presence of the parasite, even before 

 the protruding leaves unfold, is often to be found in the reddish puffs 

 or spots on the young leaves. 



Thin cross-sections through a diseased leaf will show an abundance 

 of the root-like mycelium of the fungus. (Fig. 81.) This mycelium 

 irritates the growing cells of the young leaf, causing an evident increase 

 in the number and size of the cells, as well as marked changes in their 

 form and structure (Fig. 82). These changes are apparently very 

 favorable to the growth and development of the parasite, but are most 



