OP ARTS AND SCIENCES. 173 



evidence, which conspired to render it in the highest degree 

 probable, as he thought, that at least a considerable portion 

 of our temperate flora was in existence in the early post- 

 tertiary, and even in the later tertiary times. Also, that this 

 early temperate flora then ranged much farther north than 

 now. This he thought clear, both from the species identified 

 in these deposits, and especially from the character of the 

 land animals which in those days roamed over the plains of 

 the Nebraska, consisting of Camels, Horses, an Elephant, a 

 Mastodon, a Rhinoceros, &c. ; these herbivorous animals most 

 probably feeding in great part upon herbage like that of the 

 present period, since herbaceous plants and grasses are likely 

 to be more ancient than trees. And, since these animals 

 must have had a truly warm-temperate climate. Professor 

 Gray would positively infer that, in lat. 40° - 43°, they were 

 not living anywhere near the northern limit of the temperate 

 flora ; so that the temperate flora, which now crosses the six- 

 tieth parallel in Western Europe, must have then extended to 

 at least as high latitudes in Western North America ; and 

 this would make the temperate floras of North America and 

 of Northeastern Asia essentially conterminous, and therefore 

 commingle a certain number of species. 



Subsequently, the glacial epoch, coming slowly on, did 

 not destroy the species, or at least did not destroy those 

 species which Mr. Lesquereux has identified with existing 

 ones, so that the same may be inferred of similar species. 

 Those which did survive through a period which brought 

 an arctic climate down to the northern part of the Southern 

 United States, it appeared certain to Professor Gray, must 

 have been pushed on still farther south, and between them 

 and the ice there must have been a band of cold-temperate 

 and of arctic vegetation, perhaps as broad as that now inter- 

 posed between Live-Oaks, Chinquapin Chestnuts, or Pecan- 

 trees, and the present ice. The existence at that period of 

 an arctic flora, of species identical with*the present, was 

 demonstrated by the arctic species which, retreating up our 



