342 HARPER 



the names that Linnaeus gave them, and also illustrates the 

 great activity of the nomenclature reformers in the last two 

 decades. (The differences between two such curves are probably 

 less for this region than they would be for almost any of the 

 older-settled and more densely populated parts of the civilized 

 world.) 



Conclusions. 



The most important points brought out in the foregoing 

 pages seem to be the following: 



The most satisfactory system of geographical classification of 

 the vegetation of temperate Eastern North America is one based 

 on geology. 



The coastal plain, which is defined on strictly geological 

 grounds, is probably the most distinct natural subdivision of 

 temperate Eastern North America, differing notably from all 

 other subdivisions in soil, topography, and geological history, 

 and to a corresponding extent in its flora. 



The Altamaha Grit region of Georgia is a centrally located 

 and otherwise fairly typical portion of the coastal plain, in many 

 respects homogenous and in some respects unique. Its bound- 

 aries are fairly well defined, and its flora differs perceptibly 

 from that of adjacent regions. 



The comparatively recent submergence of this region, which 

 has been demonstrated by purely geological evidence, is borne 

 out bv the phytogeographical evidence herein set forth. 



Owing to the comparative newness of the. soil, and other 

 considerations, open pine forests which give little shade are 

 eminently characteristic of the region. With this state of affairs 

 are correlated marked adaptations for reduction of transpiration 

 in most of the plants inhabiting the region. 



Similar types of soil and topography recur in all parts of the 

 region, the climate is essentially uniform throughout, and the 

 final details of plant distribution seem to be governed mainly 

 by the amount of water in the soil — which in turn depends on 

 topography — and by variations in the thickness of the mantle of 

 Columbia sand. 



All natural features of this region seem remarkably stable. 



