Ch. XV.] THEORY OF A MIOCENE ATLANTIS. 269 



If we consider not simply a mere list of species but those plants 

 which would constitute the mass of the vegetation, the European part 

 of the fossil flora is thrown still more in the background, and the fore- 

 ground is occupied by America with its numerous evergreen oaks, 

 maples, poplars, planes, Liquidambar, Robinia, Sequoia, Taxodium, 

 and ternate-leaved pines, and Japan with its many camphor trees and 

 glyptostrobus, the Atlantic Islands with their laurels, and Asia Minor 

 with its planera and Populus inutabilis.* During the Miocene period 

 in Europe, there was a singular coexistence of generic types of plants 

 which are now peculiar to America, or to Asia, or to Africa, or Aus- 

 tralia ; in a word, to parts of the globe extremely distant from each 

 other. This fusion of the characters now belonging? to distinct botan- 

 ical provinces becomes more marked as we go back to the Lower 

 Miocene formations, and will be found to be still more strikingly ex- 

 emplified in the antecedent Eocene and Cretaceous periods. In the 

 Lower Miocene formations of Central Europe the chmate seems to 

 have been not only hotter but more uniform and humid, and this 

 humidity would favor the formation of beds of lignite, such as con- 

 stitute the Brown Coal of Germany. 



The large number of American genera in the Miocene flora induced 

 Unger to suggest that the present basin of the Atlantic was occupied 

 by land, over which the Miocene plants could pass freely, and this hy- 

 pothesis has been enlarged and advocated with great ability by Heer. 

 It seems at the first glance to derive much support from the fact that 

 it is the eastern or Atlantic side of North America, or that which is 

 nearest to Europe, which presents the greatest number of vegetable 

 forms analogous to the Miocene flora. But Dr. Asa Gray, following 

 up a hint thrown out by Mr. Bentham, has argued with great force 

 that it is far more probable that the plants, instead of reaching Eu- 

 rope by the shortest route over an imaginary Atlantis, migrated in an 

 opposite direction, and took a course four times as long across Ameri- 

 ca and the whole of Asia. 



If the evidence in the botanical scale were equally balanced in favor 

 of these two opposite theories, a geologist would not hesitate to prefer 

 that of Dr. Asa Gray as demanding an incomparably smaller amount of 

 change in physical geography since the close of the Miocene period. 

 It is true that since the beginning of that era there have been vast 

 alterations in the level of the Alps and contiguous regions, as we 

 have seen, p. 260, and in the Mediterranean, especially the Egean 

 Sea, p. 247. And there was perhaps, as the late Edward Forbes 

 contended, an extension westward of European and North African 

 land even in the Pliocene period. f If, instead of assigning an 

 almost historical date to a continental condition of the area between 

 Africa and the Southern States of North America, such as might 



* Heer and Gaudin, p. 59. 



| See Map, vol. i. pi. 7. Memoirs of Geol. Survey, &c., 1846. 



