P. MACNAIR ON THE ALPINE PLANTS OF PERTHSHIRE. 243 
mountains tends to show that we must seek elsewhere for evidence of 
their original centres of distribution. Accepting the view that they 
must have been propagated from some centre, the question then 
arises—Where is the centre of distribution? It is now believed by 
many of our botanists, zoologists, and geologists that in geological 
times the various faunas and floras of which evidence is found in 
the rocks have had a boreal origin and have migrated from the north 
southwards. Now, in the case of our alpine plants, it seems that they, 
following the same law of distribution as the more ancient faunas 
of geological times, have had a similar boreal origin. Thus many of 
the plants of Lapland and Norway are specifically identical with those 
found in our Perthshire mountains, and as we trace them towards 
more southern latitudes we find they become gradually scarcer and 
eventually disappear. 
In the year 1845, Prof. E. Forbes for the first time drew attention 
to a large amount of botanical, zoological, and geological evidence 
bearing upon the present distribution of the alpine fauna and flora of 
our islands. He recognised in the occurrence of these alpine plants 
upon our mountains evidence that, during the period when they 
migrated from their native habitat to the position which they occupy 
on our mountain summits, Scotland must have been in a much more 
arctic condition than it is now, so he fixed upon the glacial age 
as the period when these plants migrated into our country. He also 
recognised in the presence of such maritime plants as Attticvtci 
muTititnci^ Cochlcai'ici gv(Zfil<xndtcci^ Plcintago iiiuvitwKi^ etc., evidence 
that a considerable submergence of our country had taken place, as 
many of these maritime plants are now found at considerable altitudes 
upon our mountains. Thus the first plant in the three we have just 
mentioned, the common sea-pink of our shores, can be found in great 
numbers, at an elevation of from 3000 to 4000 feet, upon our High¬ 
land mountains, but we have to pass from that altitude to the sea shore 
before we again meet with it. As to the other two species which we 
have mentioned having a similar vertical distribution, it was concluded, 
by Forbes, that during the period these plants were introduced to our 
country the British Islands must have stood at a much lower level; in a 
word, the distribution of these plants upon our mountains indicates the 
old shore lines at which the present land surface must have stood. The 
whole evidence, he pointed out, tended to show that when these 
plants migrated to our country it stood at a much lower level, only 
the summits of the higher mountains appearing above the sea; that 
an intense cold existed, so that this sea was filled with icebergs con^ 
taining sand, mud, and stones floated from more northern latitudes, 
and that during this period our Alpine plants managed to establish a 
footing upon our Highland summits; that gradually, as the land rose. 
