TREES AND TIMBER 



433 



gray border. The spots, from 3-6 mm. in diameter, 

 often coalesce to form large blotches which are fragile, 

 sometimes dropping from the leaf. Young leaves develop 

 poorly and are deformed, while severe infection may cause 

 complete defoliation of the tree. 



Fig. 188. — " Cedar apple," gall of the rust fungus. Original. 



Macrosporiose (Macrosporium Catalpce Ell. & Mart.). — 

 This spot is scarcely distinguishal)le from phyllostictose 

 except through the absence of pycnidia and the presence of 

 a scant quantity of black mold. 



Powdery mildew, microsphaerose {Microsphcera vacdnii 

 (Schw.) Salm.). — This shows the usual powdery spots 

 with black perithecia. 



Rhizoctoniose. Seep. 61. 



