18 PLANT LIFE OF ALABAMA, 
in his honor by Gray, which is confined to a single locality on the 
banks of the Alabama River. 
More recently our knowledge of the flora of Alabama has been 
greatly enriched by the extensive collections made by Profs. F. 5. 
Earle and L. M. Underwood in 1896, and also by those made the fol- 
lowing spring and summer by Professors Earle and Carl F. Baker. 
GENERAL PHYSIOGRAPHICAL FEATURES OF THE STATE. 
TOPOGRAPHY AND GEOLOGY.' 
Alabama, extending from the shores of the Gulf of Mexico in lati- 
tude 30° 31’ to the rim of the highlands of Tennessee under the 
thirty-tifth parallel of latitude, presents two well-marked divisions 
which nearly coincide with the northern and southern halves of the 
State, and which are readily distinguished by climatic differences, 
topographical features, and geological structure, and by the aspect of 
the vegetation corresponding with these conditions. The upper or 
northern division embraces the mountainous region of the State, which 
offers great complexity in its geological formation, almost every 
stratum of the various geological epochs being here represented. This 
gives rise to greater diversity of topography and soil than exists in 
any other of the Gulf States, thus producing that variety of resources 
which gives Alabama such a prominent position among her sister 
States. 
The lower division, which occupies the southern half of the State, 
can be considered as a vast plain of great uniformity in its general 
features; gently undulating where the loose sedimentary strata of the 
Post-Tertiary formations prevail, and broken where the cherty ridges 
of the Tertiary and Cretaceous rocks offered greater resistance to 
erosion by water. 
* 
THE COASTAL PLAIN. 
The sedimentary strata forming the Coastal plain cover three-fifths 
of the area of the State. In the lower part, in Mobile and Baldwin 
counties, this plain rises in gentle swells to 300 feet above the tide- 
water region, reaching at its northern limit an average elevation of 
about 500 feet above the sea. For a distance of from 80 to 100 miles 
from the seashore this plain is almost entirely covered with the man- 
tle of sands and gravels of the Lafayette formation, the oldest of the 
Post-Tertiary strata, which give rise to soils varying from almost 
pure sand to loamy sand and generous sandy loams, and support a 
rather uniform but magnificent vegetation of coniferous trees. To 
the north of these terrains appear the limestones and marls of the 
‘Drawn chiefly from the Reports of the Geological Survey of Alabama, 1875 to 
1896, by E. A. Smith, State Geologist. 
