PALEOBOTANICAL EVIDENCE 537 



these floras, known as the Renverian stage or flora, is Middle Pliocene in 

 age. It includes a flora, mainly of seeds and frnits, of nearly 300 species, 

 of which some^230 have been determined with a considerable degree of 

 certainty. This flora has very little relationship with the present flora 

 of Europe, the Caucasus, or the Mediterranean, but clearly finds close 

 affinity with the ^^living flora of the mountains of western China, and to 

 its allied geographical provinces — Japan, the Himalaya, Eastern Tibet, 

 and the Malay Peninsula." 



The Reids conclude that the Reuverian assemblage was a temperate 

 flora similar to that which belongs to the moist and temperate forest belt 

 found only on the Chinese mountains. The late Miocene and early Plio- 

 cene flora was originally essentially circumpolar in distribution, but in- 

 creasing cold forced it southward along at least three migration routes. 

 One path was along the mountains of Atlantic North America, a second 

 through eastern Asia, where both persist today, and which accounts, as 

 Asa Gray long ago pointed out, for the striking resemblance between 

 these two floras. The third route was through western Europe, as at- 

 tested by the remains found in the Reuverian flora ; but when increasing 

 cold forced this farther south, it was crushed out against the east-west 

 mountain ranges and disappeared. 



A slightly younger flora, and one very distinct from the Reuverian 

 flora, is the Upper Pliocene Teglian flora of Limburg. It includes about 

 133 forms, of a decidedly cool-temperate character, which bears a close 

 resemblance to the European flora of the present day. That is, all the 

 plants with Malayan and Australian affinity had disappeared, and al- 

 though a few distinctive Chinese and Japanese species still remained, by 

 Upper Pliocene time, as represented by the Cromerian from England, the 

 European facies had been fully established, the peculiar Chinese element 

 having disappeared, except for such species as still live in Europe. 



Part II. Origin and Differentiation of geologic Climates 



EARLY CLIMATES NON-ZONAL 



We have now passed somewhat hastily in review the salient facts relat- 

 ing to geologic climates as interpreted by and through fossil floras. This 

 has been supplemented and confirmed in many cases by an appeal to the 

 pronouncement of fossil faunas. It is perhaps not too much to say that 

 it has now been demonstrated beyond reasonable question that climatic 

 zoning such as we have had since the beginning of the Pleistocene did not 

 obtain in the geologic ages prior to the Pleistocene. I think this state- 

 ment of conditions is very generally accepted by geologists and paleon- 



