THE ALTAMAHA GRIT REGION OF GEORGIA 13 



The conclusion is almost irresistible that nearly all these 

 endemic forms (whether species or groups of higher or lower 

 rank) in the coastal plain must be of very recent origin. For 

 they could not have existed in their present habitats in Pleisto- 

 cene times, when the coastal plain was nearly all submerged, 

 and if at that time they grew farther inland they have left no 

 trace of the fact. The considerable number of species which 

 are not quite confined to the coastal plain but grow also at 

 a few isolated localities in adjoining regions are perhaps of 

 equally recent origin, though the evidence is not so conclusive 

 in such cases. 



The Coastal Plain of Georgia in Particular. 



There is no more typical portion of the whole coastal plain 

 than the 35,000 square miles of it included in Georgia, where 

 it constitutes the southern three-fifths of the state. This area 

 (popularly known as South Georgia) is about equally divided 

 between the Atlantic and Gulf slopes. It is equally distant 

 from Long Island and southern New England, where the coastal 

 plain formations are mostly buried beneath the glacial drift, 

 and southern Texas, where the aridity of the climate causes an 

 equally profound modification of the coastal-plain flora. 1 The 

 fact that it is also midway between the highest mountains of 

 Eastern North America, which have presumably been continu- 

 ously covered with vegetation since before the coastal plain 

 existed, and subtropical Florida, where most of our representa- 

 tives of tropical species and genera probably first entered this 

 country, has doubtless had a marked influence on the present 

 composition of the vegetation of south Georgia. 



Almost all divisions of the coastal plain strata are represented 

 in Georgia, and each is usually recognizable by its characteristic 

 topography and flora. In general the oldest strata come to the 

 surface (disregarding for the present the overlying Lafayette and 

 Columbia formations) farthest inland and at the highest altitude. 

 The strata are believed to have an average seaward slope of 30 or 

 40 feet to the mile, and their outcropping areas form elongated 



1 See Bray, U. S. Bureau of Forestry, Bull. 47: 15, 29. 1904 



