FLORA. 225 
us now into the tertiary formations. The Arctic flora of 
this epoch, which saw the Polar lands gradually cool down, 
become covered with ice, and finally extirpate all fruit- 
hearing vegetation, is the most rich in record of all those 
of which Professor Heer has published the plants found. We 
are far from being astonished at this profusion. We must 
bear in mind that in the north, as well as on the flank of 
mountains, no type of plants is represented in any degree 
by the most beautiful or magnificent individuals in 
approaching the limit marking the point of definitive 
arrest. The beech in Denmark, the pedunculated oak in 
the neighbourhood of Stockholm, the white birch in Dale- 
carlia and on to Altenfiord, the fir of the Alps, the pine 
of Norway, all supply strikiig proofs of this truth. It 
was the same of old in the Polar regions, where the ancient 
vegetation, after having been subjected from period to 
period, as everywhere else, to a gradual progress, after 
having acquired new types, and lost previous types, or 
seen the aspect of them changed and more or less modified, 
reached at length an age in which the heat began to 
decrease, in which the seasons began to show clearly their 
differences, and the hibernal night made them feel the 
effect of its long darkness, This age evidently coincides 
with the tertiary age ; but before leaving the field to the 
ice masses and giving up the extreme north to devastation 
and solitude, the Arctic climate passed through many 
phases. : 
‘ We have seen that towards the close of the chalk period 
the reduction of temperature was as yet but little felt, 
but difference of latitude tended to show itself, and to do 
so ever more strongly. 
‘We have no evidence that the palms and the dodder- 
laurels with persistent leaves, the hibernal flowering of 
which required the presence of light in the cold season, 
have ever had their habitation within the Polar Circle. 
‘From the eocene to the epoch in which these plants 
spread themselves in Europe, and advanced at least to the 
55° of latitude, the Arctic regions regions presented doubt- 
Q 
