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Igor] VEGETATION OF WESTERN TEXAS 199 
of this difference are apparent even superficially in the absence 
of certain semi-tropical species common at the south, and in 
the presence of Upper Sonoran or Carolinian species whose range 
extends into the middle northern states, 
THE RED BEDS PROVINCE.—The vast level plains of reddish, 
chocolate soil make of this province one of the most unique fea- 
tures of the entire Texas region. This geological formation 
underlies the Staked plains, and has been exposed by the ero- 
sion of that area in the Pecos and Canadian river valleys. But 
the red beds plains lie between the Staked plains and the Grand 
prairie (more accurately the upper cross timbers), a width of 
150 miles, and stretch away through Oklahoma and southern 
Kansas, a distance of 400 miles. Erosion and weathering have 
left wide, flat stretches of reddish landscape, either covered with 
fine, chocolate, silty sand, or exposing the bare rock. Violent 
bursts of rainfall wash away acres of prairie, often to the depth 
of several feet, carrying the chocolate flood silt to the coast 
country. Within the Texas region there are no large relief 
features in the red beds province, although the broad erosion 
valleys have to a certain extent the ‘‘ Bad lands” aspect. The 
great extent of this province and its geographical position give 
it climatic relations which are apparent in the character of the 
vegetation. 
As to atmospheric moisture, the stretch of 150 miles (the 
breadth of the province) from east to west means a variation in 
rainfall from 27 to 20 inches, and of evaporation capacity from 
50 to 65 inches. The vegetation of the western part of the 
Province has a more extreme xerophytic character than that of 
the eastern part. The northeastern parts sustain extensive 
mesophytic or semi-mesophytic culture formations with reason- 
able certainty. It is particularly a wheat belt. Toward the 
western border these formations become impossible except with 
seasons of higher rainfall. 
As to temperature, while the entire province falls in the 
Lower Sonoran zone, its position as a whole far to the north of 
the Rio Grande plain gives it floristic relations more in common 
