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A Journal of General Botany 



VOLUME 20 

 NUMBER 5 

 MAY, 1917 



CONTAINING 



The Physical Control of Vegetation in Rain-Forest and Desert Mountains 



Forrest Shreve 135 



Plant Associations of Western Pennsylvania with Special Reference to 

 Physiographic Relationship. II 



J. E. Cribbs; 142 



Books and Current Literature 158 



Notes and Comment 161 



PUBLISHED MONTHLY 



OFFICE OF PUBLICATION 



2419-21 Greenmount Ave. 

 baltimore, md. 



EDITORIAL OFFICE 



TUCSON, ARIZONA 



Ent«red as second-class matter March 9, 1912, at the post oflBce at Baltimore, Maryland, under the Act of July 16, 1894 



