.'502 BERRY— TERTIARY FLORAS OF THE [Apr.i ^i. 



portant elevation being that of the early Miocene which was followed 

 by a subsidence, which was, however, less in extent than those which 

 had preceded it. 



No part of the coastal plain is so favorably situated for the study 

 of the floras which preceded the present, extending backward to a 

 time which marks the first recorded appearance of angiosperms, as 

 that of the Gulf states. No single part of North America contains 

 so continuous a series of Tertiary deposits carrying fossil plants. 

 Here we find abundant floras in the lower and middle stages of the 

 Eocene, considerable floras in the Oligocene. some in the later Mio- 

 cene, and rather abundant fossil plants in the Pliocene. The Rocky 

 Mountain region is rich in Eocene fossil plants and there are some 

 Miocene floras, but no Oligocene or Pliocene floras are known. The 

 Pacific coast region likewise furnishes Eocene and Miocene fossil 

 plants but none of Oligocene age. The fossil floras of the coastal 

 plain are found in an area where it is possible to attain to some 

 measure of accuracy in predicating the general character and course 

 of ocean currents and winds and other physical features of the en- 

 vironment. On the other hand the western floras just mentioned 

 grew in areas where vulcanism was great at times ; in areas of great 

 orogenic activity, where changes in topography were numerous and 

 elevations of several thousands of feet are recorded ; areas in which 

 climatic conditions not only varied from place to place, but passed 

 through a large cycle of secular changes. All these factors greatly 

 complicate the floral history. 



The floras of the southern coastal plain are moreover checked 

 for the most part by very abundant marine faunas in intercalated 

 beds, or the plant-liearing beds which represent the coastal swamps 

 and the shallow water deposition of the old embayment merge 

 laterally with the contemporaneous limestones or marls which were 

 forming in more open waters along the coasts to the southward, so 

 that there is a considerable body of facts bearing on depth, character 

 of the bottom, and marine temperatures, with which to compare land 

 temperatures. These criteria have been admirably worked out for 

 the Florida area by Doctors Dall and Vaughan for the post-Eocene 

 and their results furnished a reliable datum plane for the deductions 

 to be derived from the studv of the fossil floras of these times. 



