100 Prof. O. Heer on the last Discoveries 



laurels and the camphor-trees only went to the shore of the 

 Baltic ; the magnolias and evergreen oaks, the walnuts, and 

 the vine advanced in Greenland to the 70th degree ; and the 

 marsh-cypress, the thuias, the poplars, the planes, and the 

 limes reached in Spitzbergen to 78°. Although several spe- 

 cies traversed all these regions from Italy to Spitzbergen, the 

 character of the vegetation was nevertheless different accord- 

 ing to the zones, without being so strongly separated as at the 

 present day, when, however, some species, such as the birch 

 and the pine, are disseminated from the north of Norway to 

 Italy. The temperature decreased much less rapidly in ad- 

 vancing towards the north, so that Spitzbergen still had a 

 temperate climate. 



In order to explain this strange phenomenon, various hypo- 

 theses, which are now subjects of discussion among naturalists, 

 have been proposed. But I cannot speak of these here, and I 

 may pass over them in silence the more easily because I have 

 already expressed my opinion upon this subject in this very 

 review*. I may, however, be permitted to call attention to a 

 third point. 



The recent discoveries made in the extreme north fully 

 confirm the law deduced from the examination of European 

 plants, that the organization of plants becomes more and more 

 elevated with the progress of time. The ancient Carboniferous 

 flora of Bear Island only consists of Acotyledons, whilst the 

 much more recent flora of the Miocene of Spitzbergen consists 

 in great part of phanerogamous plants, the organization of 

 which is higher. Moreover we see the former extending over 

 a much vaster region than the latter ; so that the habitat of the 

 species has gone on becoming restricted in the course of centu- 

 ries. The first-named plants probably issued from a primitive 

 centre ; they have in general microscopic seeds, which could 

 fly readily in all directions. The second set, the plants of the 

 Miocene, have probably been propagated starting from several 

 centres ; but their diffusion on the surface of the globe must 

 have been slower, on account of the weight of their seeds, 

 which are generally larger. One of these centres of difusioti 

 was evidently in the i^olar zone, whence iilants and animals 

 have spread in radiating directions. 



We have already seen that Spitzbergen has several species 

 in common with Greenland, as also with the Mackenzie. 

 Quite recently I have received a very interesting fossil flora 



* "Les Regions polaires du Nord," Bibl. Univ. January 1867, p. 78 

 et seq. I have treated this subject in "rreater detail before iho Society 

 IIelv6tique des Sciences Naturellea at llheinielden in 1807, and iu "Flore 

 fossilo des Regions polaires," p. (Jl et seq. 



