When we carefully examine the present range of Arctic plants in the British Islands, a curious fact presents itself which no doubt has frequently been noted by botanists, viz., that some of the most characteristically Arctic species, and some which are often quoted by glacialists in support of their theories, flourish at the present moment in very mild situations. I have already referred to the fact that the Mountain Avens (_Dryas octopetala_) abounds in the west of Ireland (County Galway) down to sea-level. Now it is well known that the mean winter temperature of that part of Ireland resembles that of Southern Europe, being no less than 12° F. (=7° Cent.) above freezing point. The plant, of course, is here a native, and not introduced. This instance shows clearly, that as long as more vigorous competitors are absent, and as long as it is not exposed to severe frost or undue dryness, this and allied species do just as well in a mild climate as in their native Arctic home. In his interesting essay on the distribution of the Arctic plants in Europe during the Glacial period, Professor Nathorst adduces the fact that all the localities but one, in which remains of such plants have been discovered, lie either within or close to the limits of the maximum extension of the supposed northern ice-sheet, or within those of the former Alpine glaciers. Whether we look upon the boulder-clay as a marine or a terrestrial product, it is quite conceivable that, in many instances, the remains of the Arctic plants may have been carried by ice to great distances from where they grew. The probability, however, is in favour of most of them having lived where their remains are now found. Now, it is a remarkable fact, that the single instance in Europe of a deposit of Arctic plants having been found far removed from the maximum extension of the northern ice-sheet is the one quoted above, viz., at Bovey Tracey, in Devonshire. Even up to recent times Arctic plants may have persisted at Bovey Tracey just as they do in Galway under the influence of a mild coast climate. Similar circumstances may have led to their survival along the shores of the sea which deposited the North European boulder-clay, while they moved northward from the Alps along with the glaciers, which always supplied them with an abundance of moisture. Alpine plants probably became exterminated in the plain of Central Europe at a much earlier period. SUMMARY OF CHAPTER V.