Land-bridge from Northern Europe to North America. 31 
maintains that a land-connexion between Greenland, Iceland, the 
Farodes, and Scotland, must have existed, because the plants could 
only have migrated from Europe over a land surface,! but to him the 
idea of a survival of plants during the Ice Age in Greenland is 
inconceivable. He therefore argues that the land-bridge could only 
have existed in Post-Glacial times. Hence the Glacial period and its 
supposed adverse influence upon the flora of Northern Europe has now 
become the mainspring of most speculations as to the former presence 
or absence of a northern land-bridge. 
The question of the supposed survival of plants through the Ice Age 
in Greenland largely depends on the problem whether or no the glaciers 
of that country had a vastly greater extension formerly than they have 
at present, and covered the whole of the land now free from ice. That 
the latter has never been entirely invaded by ice has been clearly 
demonstrated by the leader of the German Greenland Expedition, 
Dr. E. von Drygalski. The greater extension of ice in former times 
no doubt can be proved, he remarks; yet glaciers certainly never 
reached the cliffs and rock-pinnacles which abound on all parts of the 
coast-lands of Greenland.” No reason, therefore, can be adduced why 
the flora of Greenland should not have survived the Ice Age in that 
country, particularly as we have some grounds for the supposition that 
the land in the Arctic regions then stood higher than it does now. 
It would be wrong to suppose that plant migration to the Farves 
and Iceland has proceeded altogether from Europe. A stream has 
likewise advanced from the opposite direction. ‘hus in the Farées 
we find at least seven plants unrepresented in the British Islands. 
These came from Greenland and Arctic America. 
A small group of plants is of particular interest to Irish botanists, 
as being almost exclusively confined to the West of Ireland and North 
America. According to Messrs. Colgan & Scully,? the plants in 
Ireland which belong to this group include Spiranthes Romanzoviana, 
LErtocaulon septangulare, and Naias flexilis. All of these plants are 
indigenous and discontinuously distributed. An interval of more than 
200 miles separates the northern and southern stations in Ireland of 
the rare orchid S. Romanzoviana. The water plants L. septangulare 
and JV. flexilis inhabit not only some of the western Irish lakes, they 
occur also in Scotland. 
Messrs. Colgan & Scully do not explain the presence in Ireland of 
these plants as being due to any such accidental transport. They 
believe them to have reached Europe by means of an ancient northern 
land-connexion. Mr. Praeger likewise comes to a similar conclusion 
with regard to the origin of the American plant group in Ireland. 
He does not favour the theory of accidental dispersal. A land surface, 
long since destroyed, of Pre-Glacial age, appeals to him as a more 
likely explanation of the presence of the American plants.‘ 
The number of plants common to Europe and North America is 
really far greater than we imagine, though very few, as we have seen, 
' James Geikie, Prehistoric Hwrope, 1881, p. 520. 
2 EK. von Drygalski, Grénland Expedition, 1897, vol. i, p. 335. 
3 N. Colgan & R. W. Scully, Cybele Hibernica, 1898, 2nd ed., p. 71. 
4 R. Lil. Praeger, Irish Topographical Botany, 1901, p. 23. 
