34 FOREST RESOURCES OF TEXAS. 



strenuous efforts of Atlantic species to push south westward, even in 

 the face of an arid climate. The spectacle of a counter invasion is 

 presented in the case of the chaparral, which is a horde of Sonoran 

 shrubby species pushing their vanguard even into the agricultural 

 areas of the State. 



THE MESQUITE. 



Among these the mesquite is the dominant and strenuous species. 

 Its spread northward and eastward from the Rio Grande country 

 during the past fifty years has been a marked phenomenon. By its 

 invasion mile after mile of treeless plain and prairie have been won 

 and reduced to the characteristic orchard-like landscape. In the coast 

 country, and likewise in the Black Prairie region, it has passed the 

 Brazos. It has pushed northward over the Staked Plains, covering half 

 their area. Along their eastern front it has passed over Oklahoma 

 and into southwest Kansas. Miles of the level prairie in the Abilene 

 country are covered by mesquite. Large areas of the fine compact 

 soils of the granite country harbor it. San Antonio is half surrounded 

 by a "mesquite forest." Pastures about Austin are growing up in 

 mesquite. The name " mesquite flats " points to the preference of this 

 tree for low or level areas with fine compact soils, by which prefer- 

 ence it avoids competition with native woody species, which are on 

 rougher ground and more open, porous soils. 



The coming of the mesquite has brought a vast deal of wood and 

 much forage, but the agricultural areas do not need these at the price, 

 and more arid areas would be better off in the long run in open grass 

 pastures. Where mesquite is accompanied by prickly pear or other 

 thorny species, as it is to the southeast of San Antonio, it becomes 

 a serious menace to grazing interests and a heavy expense to farmers. 



This encroachment of mesquite is partially accounted for by its weed- 

 like capacity for occupying new ground, its preference for the flat 

 country and compact soils characteristic of the grass prairies, the 

 weakened condition of the grass covering due to overpasturing, which 

 handicaps it in its efforts to maintain pure -grass prairies, and by the 

 influence of cattle in scattering the beans. 



THE TIMBER OF THE CORDILLERAN REGION IN TEXAS. 



This region is a part of the South Plateau of the Rocky Mountains. 

 The more or less disconnected and isolated mountain masses which 

 rise above it frequently exceed 6,000 or 7,000 feet, and in the Guada- 

 lupes reach 9,500 feet. The region lies in an extremely arid belt, but 

 its altitude not only reduces the annual temperature but also notably 

 increases the rainfall, which by virtue of the broken and tilted strata 

 is retained to be doled out continuously, thus giving a measure of con- 

 stant moisture which permits timber growth. Of this timber growth 

 two types may be distinguished: (1) That of the foothills and slopes 



