242 TRANSACTIONS—PERTHSHIRE SOCIETY OF NATURAL SCIENCE. 
the hills to the mountains; one by one, the mountain citadels have 
fallen, the results rather of starvation within the walls than of assault 
from the enemies without, till here on the summit of Ben Lawers it 
takes its last stand in the final struggle. Along this ridge of moun¬ 
tains, many other alpine species are to be found, as Gentiaiia nivalis^ 
Salix herhacea^ Saussurea alpina^ Erigeroji alpinus^ Dry as octopetela; 
while on the Clova mountains we have many of the Breadalbane 
plants and others, which are confined to the Clova mountains alone, 
as Carex alpina^ Astragalus alpmus^ etc. 
Now, it is a remarkable fact that to the north and south of this 
ridge of mountains, stretching from Ben Lui to Canlochan, and upon 
which are found these rare alpine plants, we have other peaks rising 
to an equally high altitude, such as Ben Vorlich (3224 feet), 
Stuc-a-Chroin (3189 feet), Ben More (3843 feet). Am Binnein (3827 
feet), Ben Ledi (2875 Schiehallion (3547 feet), Ben-y-Ghloe, 
and others, which, though not absolutely destitute of alpine plants, 
are yet comparatively poor, both in species and individuals, so as to 
present a striking contrast to the alpine flora of the Breadalbane and 
Clova mountains, while in the latter regions the common plants 
grow both more luxuriantly and to greater dimensions, and on them 
grow these rarer species which we can find nowhere else in Britain. 
Out of a consideration of this problem there arise such questions 
as these:— 
How came these plants to be isolated upon the summits of our 
Highland hills ? 
Why should they be confined to this particular ridge of our 
Scottish Highlands ? 
Are they the remains of an alpine flora which at one time ex¬ 
tended over the whole of Scotland ? Or, 
Were they conveyed to the summits at a period in the geological 
^ history of Scotland when the main mass of our country 
lay buried beneath the sea ? 
These and other such questions which they invoke have been con¬ 
sidered again and again, both by geologists and botanists, but while 
on the one hand botanists are still sadly in ignorance of the laws 
which have governed the distribution of our British flora, so geologists 
on the other hand are equally ignorant of the exact physical changes 
which have taken place in our island during later geological times. We 
now turn to see how far the views of botanists and geologists, such 
as they have been set forth, offer a solution of the problem regarding 
the distribution of these plants. That they are not indigenous 
to our Perthshire mountains will be at once granted by all who 
have seen them there, the species being so few and the individuals 
so limited in numbers, while their isolated position on our Scottish 
