160 On the Campus 



summit. The result of this erosion forms a wide talus 

 around the desert, spreading great fan-shaped deposits 

 at the mouth of the canon, where immense blocks and 

 boulders choke the exit, succeeded by ever smaller rocks 

 and pebbles farther out until at length only the finest 

 silt is swept along from the widened margin far across 

 the almost perfectly level plain. 



Now it is evidently needless to say to every wisest man 

 in an ecologically minded audience such as this, that 

 every one of these peculiar topographic features, whether 

 special or not, will display its own peculiar flora. True, 

 this is not always the case; this desert must be studied 

 in its entirety, and it will require months of patient re- 

 search to even sketch its far-reaching problems. As a 

 whole the flora may be said to be that of our western 

 arid regions generally, and yet, after all, it is not just 

 like that of any other region, north, south, east, or west ; 

 not that it has peculiar species perhaps, but that it has 

 its own particular groups of species. 



Two factors, and two alone, as it seems to me, deter- 

 mine the phytology of this desert; the one, difference in 

 the constitution of the soil, referable to its geological his- 

 tory; the other, difference in level referable to the same 

 initiative. Thus there is a peculiar flora on the sands 

 whether white or red, another on the silted plains less 

 liable to transportation by the wind, another where the 

 salts emerge, whether in briny springs and fountains or- 

 as crystals whitening the surface of the ground ; another 

 for the mountain shelves, and still another for their far- 

 off summits. 



