The 



Plant World 



j\ Magazine of General Botany 



VOLUME 12 

 NUMBER lO 

 OCT. 190 9 



Containing 



Influence of Aridity Upon the Evolutionary Development of 

 Plants 



By Dr. D. T. MacDougal 217 



The Heath of Lueneburg 



By Prof. B. E. Livingston 231 



Notes and Comment 241 



Tucson, Arizona 



Entered as Second C lass Matter, Dec. 17, 1907 , at the Post-Office, Tucson, 

 Arizttna, under the Act of Congress of March 3, 187Q 



