Vegetation of the Sotol Country. 
103 
point. It forms, in the first place, a part of the southwestern 
cattle country, which with its mild winter climate is an ideal land 
for rearing herds and wintering them, its capacity limited, of 
course, by the lack of available water and sometimes of suitable 
forage, though as a matter of fact there is a great deal of forage — 
the sotol itself yielding vast quantities especially for sheep and 
goats — and after seasons of generous rainfall the grasses and an- 
nuals form almost a continuous covering of the soil in the open 
formation of sotol or lechuguilla or chaparral shrubs. In the sec- 
ond place, there is an economic interest in the possible yield of 
commercial products from certain species in the vegetation. For 
example the fibre of the lechuguilla has a well established reputa- 
tion though the production of it is yet upon a rather meager and 
primitive basis. 
TRANSITION FROM LUXURIANT FOREST VEGETATION IN EAST TEXAS 
TO THE SONORAN DESERT REGION. 
In its temperature relations, the region considered in this paper 
is part of a transcontinental belt of warm temperate climate desig- 
nated as the Lower Austral Life Zone. The zone embraces the 
South Atlantic and Gulf States and those of the Mexican boun- 
dary on both sides of the line. Because of the great difference in 
rainfall and conditions incident thereto, the former group of States 
comprising the eastern humid division, is designated as the Aus- 
tro-riparian, the latter, comprising the arid division, as the Lower 
Sonoran Life Zone as previously stated. The differences in the 
plant life of these two zones are fairly proportional to the differ- 
ence in the moisture relations of the two, in which the rainfall 
extremes are from more than 60 inches at the east to less than 
5 inches at the west. 
The State of Texas occupies the interesting position of lying in 
the zone of transition between these two extremes of the Lower 
Austral Zone. Within this State the extremes, briefly stated, range 
from the luxuriant forests of the Sabine border where the rainfall 
reaches nearly 50 inches annually and the air is moisture laden, 
to the desert mesas of the El Paso border where the annual rainfall 
is less than ten inches and the air is parched and dry during the 
season of growth. 
The more apparent phenomena of this transition are very famil- 
iar to tourists who have crossed the State on the line of the South- 
ern Pacific railway, and perhaps no section would show the transi- 
