The history of the flora of the Arctic American Archipelago. 
When :il)()i]t the middle of last century farseeing men of science — Darwin, 
J. I). IIooKKi;. and A.sa Gray — in the light of the new discoveries of the cliange- 
iihdity (.r specios and of the glaoial period and its influence, began to unravel the 
• iiiwiiuis ot (Mrcuni[)olar range and of broken areas and widely separated occurrences 
of the same spccies or alUed groups of plants, then the study of traces of glaciation 
^^'■"^ ""^ > :i<l\;>'!ced as to have clearly defined the range of the large -inland 
i( cs ol thf urcat ictMge ot the northern liemisphere. Enorraous icecaps were thought 
'•"^■^^'•^■•1 'il' ibe arctic lands of present time and to have extended far south 
nito the tenii)erate region of our days. Now we know that wide areas, with an 
arctic clnnate at the present time, do not show the faintest trace of a former gla- 
ciation, and, in some regions at least, unmistakeable signs of a postgladal period 
are iound. that cnjoyed a climate considerably warmer and more congenial to the 
devt'loi.nicnt ot vegetation than that we hve under. Moreover it bas been proved 
that (hstncTs fico from iee have existed far north of the borderline of glaciation, 
and. as already referred to, we have such an area in the Arctic Archipelago of 
America. 
The existence of such icefree areas has, indeed, made the question of post- 
glacical immigration considerably more intricate, and some phytogeographers, for 
mstanee \\ xuyusa ni Grönl. Veg. and in bis ensueing polemic with Nathorst, have 
laid much stress on their occurrence and looked upon them as having formed im- 
f)<)rtant pla.M-s ot shelter for plants from the preglacial vegetation of the area in 
qnestion. In (ireeiiland according to WARMnNo especially the high mountains of 
the sourhernmost part sliall have afforded such a centre of refuge, even if he is 
inchned to l(,ok for similar ones elsewliere also. Even if it be admitted that some 
s[»e( ies can have survived the maximum of glaciation in an especially favoured locality, 
the present Hora of the nunataks and other isolated areas of habitable ground 
liardly sj)enks m favour of looking upon the main of the Greenland flora as preser- 
v.mI Hl tliat way. The climate of such a locality naturally must be rather severe, 
and, as Wauming also admits, the species now peculiar to southern Greenland must 
have mnnigrated in postglacical time. Jn my opinion we will have to look for 
