SOME REMARKS ON THE DESERT VEGETATION OF 



AMERICA 



OVE PAULSEN 

 Copenhagen, Denmark 



Having been asked by one of the leaders of the International 

 Phytogeographical Excursion in America to publish a paper in 

 The Plant World I have pleasure in doing it — indeed I would 

 do a great deal more in order to show my gratitude for the great 

 hospitality shown to me in America, and more especially for the 

 admirable organization of the excursion and the heavy amount of 

 work done by its conductors. 



On the other hand, having no thorough knowledge of Ameri- 

 can vegetation I will restrict myself to some few remarks on the 

 desert vegetation of America. 



It was of the greatest interest to me to note the difference 

 in vegetation as the party moved westward from the east Ameri- 

 can forests, in the drier parts of which oak has displaced beech, 

 and to see in the proper order the succeeding vegetations : prairies, 

 plains, sage brush. Some years ago I travelled through Russia 

 to Transcaspia and saw the same succession: beech, oak, steppes, 

 Artemisia plain, and then came the true desert in the hottest 

 and driest regions. In America we hardly saw any desert so 

 barren and desolate as those in Inner Asia, but what came 

 nearest to it was the vegetation at Mecca, California. 



Some members of the excursion argued that what was shown 

 them as deserts were not deserts but different forms of steppes, 

 many phytogeographers regarding all xerophytic and not too 

 scattered vegetation as steppes. As I have dealt with this 

 question elsewhere I shall not enter upon it here but shortly 

 remark that, in my opinion, it is better to restrict the term 

 steppe to that vegetation which is often called grass-steppe 

 and which may, in short, be defined as a nearly closed vegeta- 



155 



THE PLANT WORLD, VOL. 18, NO. 6, 1915 





tA 



