FLORA. 27 
baccata, and certain willows, together with other plants 
which occupy now an immense area in longitudinal extent, 
show no other cause for their present diffusion ; and their 
established presence, or at least that of their direct 
homologues, in the Arctic tertiary vegetation, is a happy 
confirmation of this view. It is thus that the studies of 
Professor Heer have brought to light the geological titles 
of many European and Asiatic species, which one would 
have been ready to believe Audoohthones, and which are in 
reality only colonists and strangers of whom circumstances 
in days of old have favoured the introduction.’ 
Much interesting information is given in regard to Arctic 
vegetation of the tertiary period, and in reference to 
remains obtained from various localities it is remarked :— 
‘The unity of this flora, considered as a whole, and the 
considerable proportion of species common to different 
regions, notwithstanding the distance by which they are 
separated, and the difference in their latitudes, testifies 
that this corresponds to one and the same period, during 
which, whatever duration it may have had elsewhere, the 
Arctic vegetation, and the climate to which that vegetation 
was subjected, have experienced but slight variations.’ 
Many of the same plants are found in the miocene strata 
in Europe, and in reference to plants of the same kind 
now confined to the southern parts of Europe and of North 
America, there is supplied the following table of successive 
links connecting the vegetation of the Polar cretaceous 
period with that of the present time :— 
