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Transactions Texas Academy oe Science. 
the Devil's River into the Edwards Plateau and of the Pecos River 
into the Stockton Plateau, and farther westward the formation 
follows the foothills and eastern front of the mountains into 
Southern New Mexico. Westward to the Rio Grande at Presidio 
and El Paso the sotol formation occurs wherever the physiographic 
features with which it is identified are repeated, viz., debris cov- 
ered mountain slopes and rolling or hilly areas representing the 
progress of dissection of the plateau. 
An adequate conception of the extent and character of the sotol 
country may be gained by crossing it along the line of the South- 
ern Pacific railway, where, going westward, the sotol vegetation 
begins near the Devil’s River crossing and continues more or less 
constantly to and beyond Maxon, a distance of more than one hun- 
dred and fifty miles. 
Mr. Vernon Bailey, who has spent a portion of several seasons 
in making a biological survey of Trans-Pecos Texas, estimates that 
the area covered by lechuguilla in Texas would exceed twenty 
thousand square miles. 
The sotol country, as here defined, marks the entrance into the 
desert areas of the arid Southwest. It is, as stated, a part of the 
Lower Sonoran Life Zone. The North American deserts lie chiefly 
within this zone and some of the sotol country is of extremely 
desert character, although it would be misleading to characterize 
the whole of it as such, especially in view of the importance of 
some of it as grazing country. The region of the Great Bend is 
certainly a desert, excepting, of course, watered canyons and the 
upper mountain slopes. The Devil’s River area approximates more 
closely that of the Great Plains and differs rather in physiographic 
than in climatic conditions. Indeed the Great Plains really pene- 
trate the sotol country, for the grassy plateau of the Alpine, Marfa 
and Port Davis regions is in its vegetation essentially like the 
Staked Plains. 
The plant life of the sotol country claims a large measure of 
interest for the biologist from the fact that in such inhospitable 
regions life phenomena are accentuated by being expressed in terms 
so different from those to which most observers are accustomed. 
In the desert, living things are embodied in unusual and unique 
forms. These forms express something of the nature and force of 
desert environment. If we examine the characters of plants which 
make them seem unusual and unique, they will be found to be, in 
the main, just those which best adapt the organism to the rigorous 
environment of the desert. 
But this vegetation is also of interest from an economic stand- 
