756 FLORA OF THE PLIOCENE EPOCH. 



latitude the mean temperature has fallen 0°'9 P. From this it fol- 

 lows that at Spitzbergen, at. 78° N. lat., the mean temperature was 

 41°-9 Fahr ; in Greenland, at 70°, it was 49°-l Fahr. ; and in Iceland 

 and on the Mackenzie, in lat. 65°, it was 52°-7 Fahr. At the 

 Miocene epoch the temperature was much more uniform, and the 

 mean heat diminished much more gradually in proportion as the 

 pole was approached. The isothermal line of 32° Fahr. fell upon 

 the Pole, while now it is situated under 58° N. 



In speaking of the Polar flora of former epochs, Heer says, " Every 

 plant executes a slow and continuous migration. These migrations, 

 the starting-point of which is the distant past, are recorded in the 

 rocks ; and the interweaving of the carpets of flowers which adorn our 

 present creation retraces them for us in its turn. For the vegetation 

 of the present day is closely connected with that of preceding- epochs; 

 and throughout all these vegetable creations reigns one thought, which 

 not only reveals itself around us by thousands upon thousands of 

 images, but strikes us everywhere in the icy regions of the extreme 

 north. Organic nature may become impoverished there, and even 

 disappear when a cold mantle of ice extends over the whole earth ; 

 but where the flowers die the stones speak, and relate the marvels of 

 creation ; they tell us that even in the most distant countries, and in 

 the remotest parts, nature was governed by the same laws and the 

 same harmony as immediately around us." 



The flora of the Pliocene epoch has a great analogy to that of 

 the temperate regions of Europe, North America, and Japan.' We 

 meet with Coniferse, Amentiferse, Kosacese, Leguminosse, Rhamnacese, 

 Aceracese, Aquifoliacese, Ericace», and many other orders. There is 

 a smaU number of Dicotyledons with gamopetalous corollas. The 

 twenty species with such corollas recognised by Brongniart are referred 

 to the Hypogynous Gamopetalous group of Exogens, which in the 

 general organisation of the flowers approach nearest to Dialypetalse. 

 In this flora there is the predominance of Dicotyledons in number and 

 variety ; there are few Monocotyledons and no Palms. No species 

 appear to be identical, at least with the plants which now grow in 

 Europe. Thus the flora of Europe, even at the most recent geological 

 epoch of the Tertiary period, was very difierent from the European 

 flora of the present day. 



Taking the natural orders, which have at least four represent- 

 atives, Eaulin gives the following statement as to the Tertiary flora 

 of Central Europe. The Eocene flora of Europe is composed of 128 

 species, of which 115 belong to Algse, Characese, Pandanacese, Palmse, 

 Naiadacese, Malvaceae, Sapindacese, Proteacese, Papilionacese, and 

 Oupressinese. The Miocene flora has 112 species, of which 69 be- 

 long to Algse, Palmee, Naiadacese, Apocynaceas, Aceracese, Lauracese, 

 Papilionacese, Platanacese, Quercinese, Mjricaceas, and Abietinese. 



