^ iX s 



A Journal of General Botany 



VOLUME 20 

 NUMBER 8 



AUGUST, 19 17 



CONTAINING 



Soil Temperatures as a Factor in Ph3rtopathology 



L. R. Jones 229 



The Beginnings and Physical Basis of Parasitism 



D. T. MacDougal 238 



An Entraieration of the Pteridophytes "and Spermatophytes of the San 

 Bernardino Mountains, California 



S. B. Parish 245 



Books and Current Literature 260 



Notes and Comment 284 



PUBLISHED MONTHLY 



OFFICE OF PUBLICATION 



2419-21 Greenmottnt Ave. 



BALTIMORE, MD. 



EDITORIAL OFFICE 



TUCSON, ARIZONA 





Entered as second-class matter March 9^ 1912, at the post office at Baltimore, Maryland, under the Act of July 16, 1894 



