58 PLANT LIFE OF ALABAMA. 
crop can not be pushed, and which also presents a barrier to several 
trees and a number of other plants of Southern distribution that are 
only rarely met farther north, as, for example, the willow oak (Quercus 
phellos), loblolly pine (Pinus taeda), long-leaf pine (Pinus palustris), 
and cane (Arundinariu mucrosperima). This line, roughly extending 
from the Atlantic coast at the mouth of the Chesapeake Bay westward 
to southwestern Missouri and northern Arkansas, was located by Gray 
along latitude 36° 30’, and hy him regarded as the line of separation 
between the two principal floral divisions of eastern North America, 
namely, the flora of the northern United States and Canada and the 
flora of the Southern States. In Alabama it is only this lower belt of 
the Carolinian area, embracing the mountain region and the lower hills 
with which we are concerned. 
MOUNTAIN REGION. 
The extreme southern spurs of the Appalachian chains belong, with 
their western and eastern fronticrs, to two distinct members of this 
mountain system. Their differences in topographical and stratigraph- 
ical conditions affect visibly the distribution and localization of species 
in the sections traversed by them. 
RANGES OF HILLS OF THE METAMORPHIC AND OLDER PALEOZOIC STRATA. 
Physiographical features and climate.—The spurs which enter the 
State at its eastern boundary are the continuation of the most easterly 
of the Alleghenian ranges, and are composed of metamorphic crystal- 
line rocks skirted by the oldest sedimentary strata. They extend from 
the Coosa River to the Tallapoosa and include the most elevated parts of 
the State. The valleys reach an extreme elevation of about 1,000 feet 
above sea level, and the highest summits of the ridges reach an alti- 
tude of from 2,000 to 2,400 feet above the Gulf of Mexico. These 
ridges rise abruptly from the valleys and above the lower hills; their 
steep flanks are covered with the sharp-edged fragments of the sili- 
ceous rocks which crown their crests with bold cliffs. 
The locality of Talladega (altitude 860 feet) coincides nearly with 
the center of this subdivision. The records of daily meteorological 
observations made at this town for only two successive years are at 
hand, which are embodied in the following table: 
Date of temperature (degrees I.) and precipitation (inches) at Talladega for two years. 
Annual. | Winter. | Spring. | Summer. | Fall. 
Mean temperature. sceccc cece saceceencasae eseceecss 63.7 43.7 64 80 64.1 
Absolute maximum -. at wigigepuafosacnce 100: (eevossamsttevieesss|sueeciesesc|sieasccis 
Absolute MINIMUM .4.caveseecvaresuseezeveres cease rs 1D: Vageenss eet leeueiceces acecse aeeealeeee apes 
Mean PreciPltUOMwc0sossssaveensse dt: vasdonaee dean 49 18 11.6 10 9.98 
This mean annual precipitation can be considered ax representing 
that of the whole subdivision, with the exception of Lee County, on 
its southern border, where it rises to 54.4 inches. 
