AX CECOLOOICAL PROBLEM. 227 



impossible to define it, although the tree remains in our bogs 

 show conclusively that at one period of our country's history it 

 was as distinctly marked as it is at the present time in Scandin- 

 avia. In Norway we find appearances of the same change, for 

 at the base of its mountains, whose tops are covered with perpetual 

 snow, Taraxacum Dens-leonis and Mulgedmm alpinum grow side 

 by side, showing that even there it is possible for what we may 

 consider littoral plants to grow and reproduce their species at 

 high altitudes while we never find the converse. There is no 

 doubt that some plants are washed down the mountains with the 

 torrents and appear to flourish, as on the shores of Loch Tay, but 

 they never seem to survive an open winter. In early spring 

 these plants start into life, but as soon as they are confronted by 

 the cold winds of March and April, they quickly become 

 exhausted, and, having already spent most of their available 

 energy, are unable to continue their precarious existence ; yet we 

 see in some halophytic plants that very little protection is required. 

 The salt-laden atmosphere in the case of the sea-pink or scurvy 

 grass can be compensated under the zerophytic conditions of an 

 alpine situation by the presence of the snow, or even shelter from 

 the easterly winds in our gardens. In the case of the arctic 

 plants, for protection the flowers expand as the stem rises above 

 the leaves, and seems to go on rising until the seed is ripe or 

 growth stopped. The plant may even flower one year and ripen 

 its seed the next. In all plants the same thing is seen, but not 

 to such a marked extent with us. This peculiarity may be 

 observed in the Coltsfoot {Tussilago Far/ara), its early flowering 

 causing it to act during the arctic weather exactly as if it were 

 an arctic plant, which I have no doubt it really is. 



Suppose we take Ben Lawers as a basis for the observation of 

 these arctic-alpine plants. We find that of the above list 

 thirteen are found on its sides. If we refer to the geological map 

 we discover that the rocks, on which the majority of these plants 

 are found, are termed phylite schists, and, if we run our eye 

 along this formation as shaded on the map, we find that on many 

 of the mountains in Olen Lochay and Glen Dochart up to Beinn 

 Laoigh, this is the rock which forms the substratum for these 

 plants whenever they occur in the district, in fact, so much do 

 they seem to be confined to this formation, that one would be 



