58 ECONOMIC BOTANY OF ALABAMA. 



3. Coosa (Appalachian) Valley Region. 



(Figures 16-18.) 



This is the southwestern end of the great Appalachian 

 valley, which lies between the coal region and the Blue 

 Ridge and is over 1,000 miles long, the other end of it be- 

 ing in Pennsylvania. In Alabama it comprises the val- 

 ley of the Coosa River from the Georgia line to the north- 

 ern border of Chilton County, and several narrower val- 

 leys of similar geological formation lying a little to the 

 northwestward and parallel to it, such as Wills's, Mur- 

 phree's, Roup's, Jones's, Shades and Cahaba; in all about 

 4,000 square miles. 



References.— McC alley 5, Mohr 3 (529), Mohr 5 or 6 

 (41-42), Mohr 8 (21, 67-68), Smith 2 (83-183), Smith 3 

 (9-39), Smith 6 (27-35, 95-102, 105-107), Smith 7 (190- 

 210, 368-389, 396-402), Smith 9 (7-9, 71-77, 81-87), 

 Tuomey 1 (8-29), Tuomey 2 (27-29, 79-93). 



Geology and soils. — -The rocks of the Coosa valley re- 

 gion are mostly Cambrian, Ordovician and Silurian. 

 Strips of Devonian and Lower Carboniferous, mostly too 

 narrow to show on a state map, crop out along the edges 

 of the coal region. The strata are nearly everywhere 

 folded and faulted in a complex manner, but with a gen- 

 eral northeast-southwest strike, as already noticed in 

 Brown's Valley. The soils are very diverse in color, tex- 

 ture and fertility. The principal varieties are residual 

 gray, yellow and red clay, shale and chert. The Upper 

 Silurian sandstone ridges, such as Red Mountain, have 

 thin sandy soils much like those of the plateau region 

 already described, but deep beds of sand are rare or 

 wanting, as in the Tennessee valley. There are many 

 limestone outcrops of various ages in the valleys and on 

 mountain slopes. Some of the streams are bordered by 

 more or less alluvial soil. 



Topography and hydrography. — The topography is 

 about as varied as the geology, and closely correlated 

 with it. A prominent feature of this region, as of the 

 whole Appalachian valley, is long parallel ridges with 

 broad base-leveled valleys between them ; a decidedly ma- 



