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. S. 

 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 PHYSIOGKAPHICAL FEATURES OF THE STATE. 

 TOPOGRAPHY AND GEOLOGY. 1 



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-fifth 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 b\ 7 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 sedimentar}^ 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 



1 Drawn chiefly from the Reports of the Geological Survey of Alabama, 1875 to 

 1896, by E. A. Smith, State Geologist. 



