LEAF DISEASES AND INJURIES 27 



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wastes. U. S. Dept. Agr. Bur. Chem. Bui. 113: 1-40, pis. 1-8. 



1908. 

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Jour. Washington (D. C.) Acad. Sci. 4 : 70-71. 1914. 

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upon vegetation of atmospheric impurities in and near an in- 

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angewendeten Verfahren und ihre Wirkung auf die Vegetation. 



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1913. 



Leaf-Spots 

 Caused by various species of fungi 



There are many leaf-spots of all kinds of deciduous trees. A 

 few of the most common ones are briefly described under the 

 trees on which thej' occur (see index). The larger part of these 

 diseases, however, have not been studied and the fungi that 

 cause them are only imperfectly known. A general under- 

 standing of the nature of these diseases will suffice in most 

 cases for controlling them. Leaf-spots are mainly important 

 only when defoliation results. 



Symptoms. 



Leaf-spot diseases are characterized by the formation of dead 

 areas in the tissue of the leaf. These areas may be small or 

 large and round, angular or irregular. The color of the dead 

 tissues varies from yellowish to all shades of brown and almost 

 black. Zones of various shades of the same colors may occur in 

 the spot. The dead tissue often becomes broken and falls out, 

 leaving ragged holes. Sometimes when small round dead areas 



