TRANSACTIONS OF WAGNER 



42 



THE LIFE FEATURES OF THE COASTAL PLAIN AND THE PIEDMONT 



These forms are now quite restricted to the above-mentioned regions. Re- 

 mains of more widely distributed types, as the plane tree (Platanus), the bass- 

 wood {Tilia), the persimmon (Diosyprus), besides several varieties of birch 

 {Betula), aspens (Populus), oaks (Quercus), and beeches (Fagus), have also 

 been discovered in Greenland, indicating the existence of a rich and varied 

 woodland not unlike that of the modern temperate zone forests of Eurasia and 

 North America.* 



As Professor Berry has pointed out, there is evidence that a rich tropical 

 vegetation flourished along the shores of the old Mississippi embayment three 

 million years ago, and it is probable that this circumpolar warm temperate type 

 was developed during the same time and continued throughout the succeeding 

 Miocene and Pliocene periods. Secular changes of cHmate occurred, as we 

 know, several times throughout the Pleistocene, covering vast periods of time, 

 and marked by four distinct glacial epochs. It is not unlikely that the present 

 conditions of cHmate and vegetation in the northern hemisphere may be of 

 inter-glacial character, similar in many respects to the inter-glacial epochs of 

 the Pleistocene. The lowering of temperature at the outset of glaciation un- 

 doubtedly had a marked effect on this circumpolar Tertiary forest, blotting it 

 out entirely in the more northern part of the area, while it still continued to 

 flourish farther to the south, the hardwoods acquiring a deciduous habit with 

 the rhythmic recurrences of seasonal cold that marks our present year. Dr. 

 John Harshberger, in a most suggestive paper on the "Origin of our Vernal 

 Flora, "t has shown that in all probability the present rhythm of vegetational 

 function in northern lands had its origin in the conditions of seasonal tempera- 

 ture during the last glacial period. 



Throughout the lapse of the Tertiary the slow upwarp of the continental 

 platform along the eastern and southern Atlantic border was gradually adding 

 new land, the sands and clays of the marginal sea-floor becoming a Coastal 

 Plain land surface. A forest would find favorable conditions on this new land 

 and would spread out from the lower southern portion of the Piedmont, the 

 various types developing in situations determined largely by the nature of soils. 

 Pines and scrub oaks would spring up and cover sand tracts, as we have seen; 

 other forms would find suitable rootage in the deep alluvial soils of stream 

 bottoms and the side slopes of mature valleys both on the Piedmont and the 



*"The Relations of North American to Northeast Asian and Tertiary Vegetation." Article 

 V in Darwiniana, by Asa Gray, 

 t" Science," [N. S.] 1895, i, q2. 



