FLORA. 225 



us DOW 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- 

 bearing 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 striking 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 



