﻿ON THE BOTANY OF JAPAN. 447 



days ; indeed the temperate flora, which now in Western Europe touches the Arctic 

 Circle, must then have reached equally high latitudes in Central or Western North 

 America. In other words, the temperate floras of America and Asia must then have 

 been conterminous (with small oceanic separation), and therefore have commingled, 

 as conterminous floras of similar climate everywhere do. __y 



At length, as the post-tertiary opened, the glacier epoch came slowly on, — an extraor- 

 dinary refrigeration of the northern hemisphere, in the course of ages carrying glacial 

 ice and arctic climate 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 feUows, or such as survive, 

 must have been pushed on to lower latitudes as the cold advanced, just as they now 

 would be if the temperature were to be agam lowered ; and between them and the 

 ice there was doubtless a band of subarctic and arctic vegetation, — portions of which, 

 retreating up the mountains as the climate ameliorated and the ice receded, still scantily 

 survive upon our highest Alleghanies, and more abundantly upon the colder summits 

 of the mountains of New York and New England : — demonstrating the existence of 

 the present arctic-alpine vegetation during the glacial era ; and that the change of cli- 

 mate at its close was so gradual that it was not destructive to vegetable species. 



As the temperature rose, and the ice gradually retreated, the surviving temperate 

 flora must have returned northward -pari passu, and — which is an important point — 

 must have advanced much farther northward, and especially northwestward, than it now 

 does; so far, indeed, that the temperate floras of North America and of Eastern Asia, 

 after having been for long ages most widely separated, must have become a second time 

 conterminous. Whatever doubts may be entertained respecting the existence of our 

 present vegetation generally before the glacial era, its existence immediately after that 

 period will hardly be questioned. Here, therefore, may be adduced the direct evidence 

 recently brought to light by ^Ir. Lesquereux, who has identified our Live Oak ( Quercus 

 virens). Pecan {Carya olivceformis), Chinquapin (Castanea jiumila), Planer-tree (Planera 

 Gmelini), Honey-Locust (Gleditschia triacanthos), Prinos coriaceus, and Acorus Calamus, 

 — besides an Elm and a Ceanothns doubtfully referable to existing species, — on the 

 Mississippi, near Columbus, Kentucky, in beds which Mr. Lesquereux regards as an- 

 terior to the drift. Professor D. D. Owen has indicated their position "as about 120 

 feet lower than the ferrugineous sand in which the bones of the Megalonya; Jeffersonii 

 were found." So that they belong to the period immediately succeeding the drift, if 

 not to that immediately preceding it. All the vegetable remains of this deposit, which 

 have been obtained in a determinable condition, have been referred, either positively or 



