92 



SCIENCE. 



[-N.S. Vol. XXI. No. 525. 



unique, intact, forever changing-, yet the 

 same forever. 



Added to these peculiar and special topo- 

 graphic details of this surprising desert 

 we have, of course, those less noteworthy, 

 the common every-day features of desert 

 make-up : we have mountain slope, rocky 

 fields and hillsides, eroded valleys, marshy 

 sinks, where lose themselves the vanishing 

 torrential streams; wide plains of marly 

 clay, belts of sand-dunes, red sands, yellow 

 sands, also shifting and moving, but, better 

 subservient to the vegetation of the region, 

 these present simply vast fields of low 

 hills or hummocks ten to twenty feet in 

 height, separated on every side by tortuous 

 valleys, winding in labyrinthine fashion, 

 wind-swept, hard and bare. 



One other topographic feature must yet 

 be added to complete our picture. The 

 forces of erosion even along the mountain 

 walls have kept pace fairly well, at least, 

 with the changes in level. Great canons 

 break back even through the hard, encri- 

 nitic limestones, dividing again and again 

 where the waters have carved the rugged 

 pathway by which the explorer may reach 

 the mountain 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 Ixndders choke the exit, suc- 

 ceeded by ever smaller rocks and pebbles 

 farther out, until at length only the finest 

 silt is swept along from the widened mar- 

 gin far across the almost perfectly level 

 ])lain. 



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 research 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, determine the phytology of this desert; 

 the one, difference in the constitution of 

 the soil, referable to its geologic history; 

 the other diflt'erence in level, referable to 

 the same initiative. Thus there is a pecul- 

 iar 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 whit- 

 ening the surface of the ground; another 

 for the mountain shelves ; and still another 

 for their far-otf summits. 



The El Paso Northeastern Railway passes 

 the desert on its eastern side. There are 

 two stations on the line where for several 

 miles in every direction the surface is a 

 red-brown sand. One of these stations has 

 been by the railroad people appropriately 

 named Desert, the other is Escondida. The 

 level of the two stations is the same, 4,000 

 feet, and the flora is identical, although 

 the points are thirty miles apart. Each, 

 however, is by itself unique and entirely 

 separate from the other. The dominant 

 species is Yucca radiosa, so much so that 

 these points are called the yucca desert. 

 Of course, the almost ubiquitous mesquite 

 is there and Airiplex cancscens and Arte- 

 misia sp. f There are other species, to 



be sure, such as forms of Chrysotharnnus 

 and Ephedra, but the plants first named 

 give to the plain its character as far as 

 vegetation goes, and in topography as well ; 

 they not only thrive here and come to 

 abundant flower and fruit, but they hold 

 these peculiar sands otherwise driven about 

 the world by desert winds. 



