y;^^^^^^^ ^ 



VOLUME 21 

 NUMBER 10 

 OCTOBER, 1918 



CONTAINING 



The Origination of Xerophytism. D. T. MacDougal and H. A. Spoehr. 245 



The Classification of Symbiotic Phenomena. W. B. McDougall 250 



A Simple Non-Absorbing Atmometer Moimting. Earl S. Johnston 257 



Books and Current Literature 261 



Notes and Comment 264 



PUBLISHED MONTHLY 



OFFICE OF PUBLICATION 



2419-21 Greenmount Ave. 



baltimore, md. 



EDITORIAL OFFICE 



TUCSON, ARIZONA 



Bntered m leeond-class matter March 9, 1912, at the post office at Baltimore, Maryland, under the act of July 18, 1894 



