334 A. Gray—North American Flora. 
skiéld that, anterior to the Glacial period, Europe was ‘ bounded 
on the south by an ocean extending from the Atlantic over the 
present deserts of Sahara and Central Asia to the Pacific,’ all 
chance of these American types having escaped from and 
reéntered Europe from the south and east seems excluded. 
Europe may thus be conceived to have been for a time some- 
what in the condition in which Greenland is now. . . . Green- 
land may be referred to as a country which, having undergone 
extreme glaciation, bears the marks of it in the extreme pov- 
erty of its flora, and in the absence of the plants to which its 
southern portion, extending six degrees below the arctic circle, 
might beentitled. It ought to have trees and it might support 
i iati way has 
been open for their return. Europe fared much better, but 
has suffered in its degree in a similar way.”* 
Turning to this country for a contrast, we find the continent 
on the eastern side unbroken and open from the arctic circle to 
the tropic, and the mountains running north and south. The 
vegetation when pressed on the north by on-coming refrigera- 
tion had only to move its southern border southward to enjoy 
its normal climate over a favorable region of great extent; and, 
upon the recession of glaciation to the present limit, or in the 
oscillations which intervened, there was no physical impediment 
to the adjustment. Then, too, the more southern latitude of this 
country gave great advantage over Europe. The line of ter- 
pleasant places,*and the goodly heritage remains essentially u2- 
im paired. 
The transverse direction and the massiveness of the moun 
tains of Europe, while they have in part determined the com 
parative poverty of its forest-vegetation, have preserved there 
a rich and widely distributed alpine flora. That of Atlantic 
or in cool ravines of moderate elevation; the maximum alti- 
tude is only about 6,000 feet in lat. 44°, on the White Moun- 
tains of New Hampshire, where no winter snow outlasts 
summer. T'he best alpine stations are within easy reach of 
Montreal. But as almost every species is common to Hurope 
and the mountains are not magnificent, they offer no great 
attraction to a Kuropean botanist. 
Farther south, the Appalachian Mountains are higher, 
* This Journal, |. ¢., 194. 
be- 
aa le gear ale EAM TAL 
