1890. j 
169 
[Upham. 
differentiation toward each end, accords with the testimony of the 
raised beaches of Labrador, Greenland and Grinnell Land, with re- 
cent marine shells 1,000 to 2,000 feet above the sea, which show 
that during the Glacial period the Baffin bay region, after having 
stood much higher than now, as is known by its fiords, sank far be- 
low its present level, and during the postglacial epoch has been again 
uplifted. But the derivation of the plants of the Faeroes, Iceland 
and Greenland from Europe could not have taken place through the 
agency of sea currents nor winds, which would the rather favor 
their coming from America ; and therefore botany seems to contrib- 
ute to geology the proof that the great preglacial elevation of the 
northeastern Atlantic region, unlike that of western Greenland and 
Labrador, continued through the Ice Age, the spaces which are now 
sea between Greenland and the British Isles having become sub- 
merged, as pointed out by James Geikie, during the recent epoch, 
after affording a land passage for the European flora. 
The entire basin of the Red river of the North was covered by 
the ice-sheet, which also extended south to Saint Louis and south- 
westward beyond the Missouri river at the time of its maximum 
area in the early part of the Glacial period, and to Des Moines, 
Yankton, the Coteaudu Missouri, and the Elbow of the South Sas- 
katchewan at the time of its later great incursion, when it formed 
the terminal moraines that stretch across the upper Mississippi and 
upper Missouri regions, western Manitoba, and Assiniboia. Arctic 
and boreal plants were driven south during these epochs to the cen- 
tral part of the United States, and at the close of the Ice Age they 
followed the receding ice-sheet and again took possession of the 
great northern region from which they had been expelled. With 
the restoration of a temperate climate throughout the northern 
United States and southern Canada, the Arctic species found them- 
selves no longer able to survive there, excepting on the cool heights 
of mountains, notably the White Mountains and the Adirondacks, 
and, in the case of a few species, on the cool high northern shores 
of lake Superior and on the adjacent Isle Roy ale. These stations 
of Arctic plants are divided by several hundreds of miles from their 
general northern range. We may also class with these the isolated 
southern stations of northern species observed in Minnesota and 
adjoining states, as the white pine and balsam fir, Adoxa Moschat- 
ellina, L., Mertensia paniculata, Don, and Phegopteris calcarea, 
Fee, which, with other northern species, are found on bleak river- 
