70 PLANT LIFE OF ALABAMA. 
main channels of drainage have cut their bed through to the Subcar- 
boniferous limestone. The calcareous strata constitute the floor of 
the wide valleys of erosion by which the diverging ranges are separated 
and also of their foothills. 
VEGETATION OF THE PLATEAUS, MOUNTAIN SLOPES, AND HIGHER VALLEYS. 
Xerophile forests.—An uninterrupted forest of a varied growth of 
deciduous-leaved trees and evergreen cone bearers originally covered 
this subdivision. On the broad expanse of the table-lands above 900 
or 1,000 feet the tan-bark or mountain oak largely prevails, associated 
with post oak and Spanish oak, or more rarely with black-jack and 
black ouk, occasionally with scarlet oak, a rare tree in this State; also 
with mockernut, pignut hickory, and fine chestnut trees (the latter rap- 
idly disappearing, having been eagerly sought for on account of their 
durable timber for fencings or wantonly destroyed for the nuts), 
and with white oak (Quercus alba) and highland gum (WVyssa sylvatica). 
Among the tree growth of smaller size the sourwood (Oxydendrum 
arboreum) is most frequent, here attaining its largest development, not 
infrequently becoming 40 feet in height and over a foot in diameter; 
together with dogwood, persimmon, sassafras, and the Southern pale- 
bark maple (Acer leucoderme), and in localities with a deeper soil, the 
Northern sugar maple (Acer saccharum barbatum), tulip tree, box elder 
(Acer negundo), and angelica tree (Aralia spinosa). On Sand Mountain, 
in Cullman County, where these forests have been more closely inves- 
tigated, the woodlands support from 25 to 35 timber trees of various 
species per acre, affording from 5,000 to 6,000 feet B. M. of merchant- 
able lumber of all grades, the largest amounts being derived from the 
Spanish oak and the less valuable black oak (Quercus velutina). The 
lumber finds a ready market in the mining districts. 
Wherever the mountain oak prevails pines are rarely seen. On the 
ridges of a lower altitude, with a thinner soil, the short-leaf pine 
(Pinus echinata) forms from 20 to 30 per cent of the timber growth, 
and, together with the loblolly pine (Pinus taeda), supplies pine lumber, 
which always finds a ready market. Dense groves of the latter cover 
the shallow depressions deficient in drainage, which are particularly 
frequent on the Warrior table-land. On these swales, from a fraction 
of an acre to several acres in extent, the loblolly pine arrives at its 
perfection, scarcely surpassed anywhere in its dimensions and in the 
quality of its timber. The trees average about 24 inches in diameter, 
with a height of from 110 to 120 feet, the trunks free of knots fora 
length of from 45 to 70 feet and with but a small proportion of 
sapwood. 
The scrub pine (Pinus virginiana) is found on the most broken and 
poorest places at an elevation mostly above 1,200 feet, and is not 
frequent. 
