14 A PLANT-DISEASE SURVEY IN TEXAS. 



ranging in color from black to chocolate. They are of residual 

 origin. 



The coast prairie region is succeeded by the Tertiary forested area, 

 which extends from Bastrop County in the northeast to the south- 

 west. It includes a considerable part of the post-oak lands of the 

 lignitic belt. The region is much more hilly than the coast prairies, 

 and the rise in elevation is gradual. The southern portion is level 

 or only slightly rolling and less forested than the more hilly northern 

 part. 



The soils in this area are mainly residual, varying according to the 

 character of the underlying formation. In various localities may 

 be found sands and sandy loams well adapted to truck crops, as in 

 portions of Bastrop, Caldwell, Gonzales, and Wilson Counties. Clays 

 and clay loams may also be found, while rich alluvial soils occur along 

 the river valleys. 



A narrow extension of the rich Cretaceous prairies of northern 

 Texas extends southward through Williamson, eastern Travis, Hays, 

 Comal, and Bexar Counties. The typical soil is black and waxy, 

 derived from the underlying Cretaceous chalks, clays, and marls. 

 The land is exceedingly fertile and produces good yields of cotton 

 and corn when there is sufficient rainfall. 



The region investigated includes a small part of the Llano country, 

 in the northwest along the Colorado and Llano Rivers and north of 

 the Edwards Plateau. The region is rough and hilly, with low 

 mountains, the elevations ranging from 1,000 to 1,800 feet. The 

 underlying rocks are largely granite. In many places they are 

 sparsely covered with soil, but the valleys in many localities have 

 fertile soils suitable for the culture of a variety of crops. 



The northwestern portion of the region south of the Llano country 

 is occupied by the southern extension of the Edwards Plateau. The 

 region extends west and northwest from the Balcones escarpment, a 

 line of cliffs or hills which terminate abruptly just west and north 

 of a line connecting Austin, San Antonio, and Uvalde. In contrast 

 to the Llano country, the region is essentially a limestone country 

 and is rough and rugged, being cut by the rivers which have their 

 source in this region. The rivers which cross the area under investi- 

 gation either originate in the Edwards Plateau or rise at the base of 

 the escarpment. The Edwards Plateau is poorly adapted to agri- 

 culture, since it is a rugged, hilly country, with scant soil in many 

 places and a rainfall which ranges from 20 to 25 inches. 



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