PRESENT PROBLEMS IN PLANT ECOLOGY 1 



IV. Problems of Local Distribution in Arid Regions 



PROFESSOR VOLNEY M. SPALDING 

 Desert Botanical Laboratory 



The physical conditions prevailing in arid regions are 

 such as render it unsafe to admit without further investi- 

 gation generalizations regarding their plant life which 

 have been drawn from studies conducted elsewhere. This 

 is sufficient justification of an attempt to analyze certain 

 problems which confront the student of desert ecology in 

 his efforts to apply knowledge or principles drawn from 

 previous experience. These problems have the advantage 

 of a certain clearness of definition, which corresponds in 

 a way with the sharp features of the desert and its char- 

 acteristic vegetation. Their solution may involve great 

 difficulties, and some of them, with our present methods, 

 may be incapable of solution, but they are, at all events, 

 capable of clear statement. 



In the attempt to present such a statement, which may 

 or may not prove successful, I shall for the present limit 

 the discussion to the desert country of the southwestern 

 United States, for the sufficient reason that my own 

 studies have been conducted in that region; and I shall 

 omit all consideration of the higher elevations of the 

 mountains, which, though in the desert, are not of it; so 

 that whatever is said at this time will be understood to 

 apply to the floor of the desert, that is the great plateaus 

 and valleys which from Texas to California lie between 

 the mountain peaks and ranges, together with the long 

 slopes and low hills which border them on every hand 

 and form the natural approach to the mountains. 



1 A series of papers presented before the Botanical Society of America, 

 at the Baltimore meeting, by invitation of the council. 



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