74 



ECONOMIC BOTANY OF ALABAMA. 



of the larger rivers, and on uplands remote from streams 

 — to rather hilly, and is all due to normal erosion. The 

 streams are of all sizes, from the numerous small clear 

 branches to the large muddy rivers which rise in the 

 mineral region and cross this belt almost at right angles. 

 Most of them are bordered by more or less swamp. 

 Springs are fairly common, but all small. 



Climate. — The average temperature is about 63°, the 

 length of the growing season (which of course varies 

 considerably with latitude) from about 205 to 240 days, 

 and the average annual rainfall about 50 inches. The 

 summers are about as dry here as in the Tennessee val- 

 ley, or even drier in the northwestern portion. The cli- 

 matological data for Tuscaloosa, given in the table, prob- 

 ably represent the average for the whole region pretty 

 well. 



Forest types. — These include dry pine, oak and hickory 

 woods on the uplands, richer woods with beech, white 

 oak, sweet gum, etc., on bluffs and in ravines or valleys, 

 non-alluvial swamps along the smaller streams, small 

 areas of muddy alluvial swamp near some of the rivers, 

 and the usual river-bank vegetation. Fires are rare in 

 the valleys but moderately frequent on the uplands, es- 

 pecially where the long-leaf pine grows. 



LIST OF TREES. 



