in its relations to that of North America. ) 197 
Separation), and therefore have commingled, as conterminous 
ere do. 
At length, as the post-tertiary opened, the glacier epoch came 
_ Slowly on,—an extraordinary refrigeration of the northern hem- 
- isphere, in the course of ages carrying glacial ice and arctic cli- 
mate down nearly to the latitude of the Ohio. The change was 
evidently so gradual that it did not destroy the temperate flora, 
at least not those enumerated above as existing species. ‘These 
and their fellows, or such as survive, must have been pushed on 
to lower latitudes as the cold advanced, just as they now would 
if the temperature were to be again lowered; and between 
them and the ice there was doubtless a band of subarctic and 
sone = HeTIOd 
"therefore, may be adduced the 
light by Mr. Lesquereux, who has 
recently brou ht to_ : 
i meen ? , virens), Pecan (Carya olive-for- 
identified our liv 
wish, Channon (neaaees umala), Planer-tree (Planera Gme- 
