Igor | VEGETATION OF WESTERN TEXAS 201 
individuality as compared with the Grand prairie on the east and 
the Edwards plateau and the Staked plains on the south and 
west. It is probable that there is a real distinction, and that it 
lies chiefly in the peculiarities of the red beds formation. Two 
specific formations are constantly to be distinguished, (1) the 
Hilaria Jamesit formation, which occupies the lower stretches 
where sandy loam lies deeper, and appears like a vast field of 
heavy cultivated hay; and (2) the Aristida fasciculata formation, 
which occurs on ridges alternating with the lower areas of 
FAitlaria Jamesti, and in its turn presents large tracts of waving 
grass fields. 
Formations of prairie annuals—It is not possible at present to 
say to what extent or wherein the prairie annual formations are 
distinct from those of other provinces. The soil conditions are 
such as to favor many species devoted to sandy soils. In the 
southern part of the province there are species from the south 
and southwest. At the north the prairie annual flora of Okla- 
homa and Kansas, in the same longitude, appears to be largely 
predominant. These formations prevail in such abundance in 
the case of some species as to form an important factor in the 
forage supply, especially in the early spring, when there is a 
solid mass formation. This disappears before the climax of the 
grass vegetation season (fig. 17). 
The Great plains proper.— There are included in this region 
three provinces of the higher plains, namely Edwards plateau, 
the Staked plains, and the Stockton plateau (fg. 7). 
THE Epwarps PLATEAU.—This province forms the continua- 
tion of the Great plains east of the Pecos, from the southern 
limit of the Staked plains to the downfall at the Balcones escarp- 
ment overlooking the Rio Grande plain. The entire southern 
half between the Colorado and Devils rivers is marked by such 
deep erosion as to be mountainous. While a grazing country, 
this is not characteristically a grass plains, but a timbered area, 
and hence to be discussed especially under timber formations. 
But the grass vegetation even here contests for predominance, 
except on the most rugged hills. 
