54 ECONOMIC BOTANY OF ALABAMA. 



region, and when the water is low enough the influence 

 of the limestone in such streams is perceptible.* 



Climate. — Judging from the records for Cordova, 

 which is pretty centrally located in the basin region, the 

 average temperature is about 61°, the rainfall 53 inches, 

 and the summers a little drier than the winters. The au- 

 tumn months are the driest, as in most other parts of the 

 eastern United States. 



Forest types. — The forest types can be correlated pret- 

 ty closely with the topography. There are dry oak and 

 pine woods on the uplands or ridges, dense thickets of 

 cliff pine on the brows of many of the bluffs, a consid- 

 erable variety of trees on the lower slopes of the same 

 bluffs and in ravines, and still other kinds in the valley 

 bottoms and on the banks of rivers. 



In the northeastern half of Walker County, and ex- 

 tending a short distance into Winston and Jefferson, 

 there is, or has been, a splendid long-leaf pine forest cov- 

 ering part of several townships, remarkably similar in 

 appearance to some of the open pine forests within 100 

 miles of the coast. (See figure 14.) f Although not very 

 far from the coastal plain, its presence does not seem to 

 be correlated with any outlying patch of coastal plain 

 deposits, for the soil is apparently nothing but a resi- 

 dual sandy loam derived from the Coal Measures, and 

 does not differ materially from that of the plateau region. 



On the shale bluffs of the Warrior River in Tuscaloosa 

 County one finds a remarkable number of trees and 

 shrubs belonging to species that are commonly supposed 

 to be lime-loving; but a recent analysis of a typical speci- 

 men of the rock showed only 0.42% of lime (computed 

 as CaO). The percentage of potash (K.O) was much 

 higher, 3.95%, and may possibly be the significant fac- 

 tor in this case. 



Fire is less frequent in the basin than on the plateau, 

 no doubt chiefly on account of the more broken topo- 



*0n Oct. 16, 1911, the Locust Fork of the Warrior River near 

 Palos, Jefferson Co., looked as blue as the outlet of a large lime- 

 stone spring. 



fFor additional information about this isolated area of long-leaf 

 pine see McCalley 2 (58, 129), Mohr 5 or 6 (42), Mohr 8 (91), 

 Smith 6 (108), Smith 7 (404); especially the first-named. 



