470 FLORA OF NORTH AMERICAN FOREST REGION. 



reappears in the Crimea and the Caucasus, but is absent from Russia, 

 except in the western provinces. 



The flora of France passes by gradual changes to that of Kams- 

 chatka, which reproduces closely the plant life of Northern and 

 Central Europe. In Kamschatka the birch is dominant, and 

 there, as in Northern Scandinavia, there is a belt of fir and larch 

 in the middle of the peninsula, while the same species of berry- 

 bearing plants occur in the forests; and the marshes contain the same 

 dwarf willows. Thirty per cent, of European species of vascular 

 plants occurs in Siberia, while only 15 per cent, of the indigenous 

 plants of the N.E. of the United States are identical with those of 

 Europe. The northern limit of the birch nearly coincides with trees 

 with acicular leaves. In Siberia the larch advances beyond this limit, 

 for it begins to grow at a lower temperature than other leafy trees. 

 The growth of wheat coincides with limit of the oak, which forms 

 a large forest belt in Russia from the Gulf of Finland towards the 

 Steppes, but the Ural Mountains, low as they are, stop it from pene- 

 trating further. Grisebach thinks it doubtful whether the forest 

 areas of the Palsearctic region can be sub-divided into restricted natural 

 floras. 



North American Forest Region. According to Dr. Asa Gray, 1 

 the true divisions of the forest region are those formed by the 

 Atlantic, the Yabloni Mountains, the Pacific, and the Sierra 

 Nevada of North America. Of forest trees Europe has 7 genera 

 and 17 species Coniferous; Non-Coniferous, 26 genera and 68 

 species. But Europe wants the characteristic types of the great 

 Appalachian land, now forming the American Atlantic States. It 

 has no Magnolia, Liriodendron, Asimina, Negundo, or ^Esculus. 

 It wants the characteristic .leguminous trees known as locusts, 

 honey locusts, Gymnocladus and Cladrastis. It has no Nyssa, 

 or Liquidambar ; no tree referable to the Ericaceae ; no Bumelia, 

 Catalpa, Sassafras, Osage Orange, Hickory, or Walnut ; and no 

 ConifersB referable to the hemlock spruce, Arbor vitse, Taxodium, 

 or Torreya. Most of these types have lived in Europe in past 

 Tertiary periods of geological time. The Miocene flora, as Unger 

 demonstrated, has remarkable resemblances to that of North America. 

 This led him to argue that the sunken island of Atlantis of Plato 

 might have been a geological reality, and although we are not 

 pledged to this hypothesis when the elevation of land to the north of 

 Europe or between America and Asia offers more probable alternatives, 

 we still must admit that the existing forest vegetation of North 

 America is a survival of the Miocene forests. This American 

 flora occurs fossil round the North Pole, in Greenland, Iceland, 

 Spitzbergen, and includes with the Magnolias, Hickories, Sassafras, 

 and Southern Cypress, Californian trees like the Sequoias, and others, 

 now peculiar to Japan and China, like the Ginko trees, associated 

 with pines, maples, poplars, birches, and lindens, which Asa Gray 

 accepts as ancestors of the American temperate flora. The vegetation 

 1 Bull. U.S. Geol., and Geogr. Survey Territ., vol. vi. p. I. 



