166 
have a wider distribution, and the last probably is a late arrival and cannot live in the 
far north. Against these the southwestern islands can muster the whole group 
SW, 35 species, all of whieh most probably are låter immigrants, dating back to a time 
when the amelioration of the elimate had proceeded soraewhat farther than in early 
postglacial time, perhaps even they may have arrived 'there first during the warmer 
period and are more or less retreating now. Generally they are pronounced americnn 
types. even if some of them reach Asia and even Europé, but as table V shows 
only very few of them are represented in Greenland. 
Considerably låter, when icefree land had appeared between the remnant oF 
the Keewatin icesheet and that of Labrador, plantmigration could begin to take 
place northward along the western side of Hudson Bay. Some species of the 
groups E and E 2 may perhaps be immigrants which have used that way, espe- 
cially such as are spread also some distance to the west, for instance to Boothia 
Felix, bnt it is hardly possible to discern them from those which have passed over 
Labrador and Hudson Strait after the retreat of the Labrador icesheet, the more 
so as the Hudson Strait glacier disappeared so late. The plants we have first to 
look to as innnigrants from eastern America over Labrador must be the 11 species 
of group E, and as nine of them still live along the coast or in the raountains of 
the eastern United States and Canada, this indeed confirms the assumption so as 
hardly to leave any doubt about the way they have taken. Two of them Dryop. 
teris fragrans and Woodsia glahella, show a distribution in Greenland similar to 
that of the western species (see table VI), and the others have arrived in North 
Devon or Ellesmereland, but their Greenland area is of variable description, so as 
to make other lines of immigration thither at least equally plausible. Finally two, 
Arenaria ciliatn and Sagina intermeåin, are not found to the south in eastern 
America. They may not have reached any alpine stations, or also they are over- 
looked and may still be found to grow in the mountains of the east. 
The plants of group E 2 are more difficult to account for. I have placed 
them under this heading in table V principally because they are not found in the 
southwestern islands, but it is hardly probable that more than two or three, Carex 
capillarw and G. glareosa, and perhaps Atropis distans, actually have wandered 
along the eastern way to Ellesmereland. All the others have a more or less deci- 
dedly western distribution on the Continent, and I cannot but think that they will 
some time be found spread over the western part of the Archipelago. Thus they 
would make the dominance of the western element still more prominent. In Green- 
land these species are rather uniformbly spread. Some of the ubiquituous species 
may have arrived along the eastern way besides from the west. Of the 18 species 
of group S three are already considered, the 15 others most probably are to be 
looked upon as immigrants from the west which have spread along the coast and 
in the southern islands, but which have not been able to reach northward. As far 
as Greenland is concerned they represent rather differeiit cases, four are entirely 
absent, naraely, AstragnJus alpinus, Chrysnnthemum integrifolium, Hierochhé paucijtora, 
