DISTRIBUTION OF PLANTS. 281 



rathrum^ Teucrium montanum, Poa alp'ma, and Stellera 

 Passer ina^ would soon diffuse themselves irom our calcareous 

 hills to the flat country, and even over our porphyry moun- 

 tains. 



It is true that mountain tracts commonly form the boun- 

 daries of Floras. But this happens, not because these moun- 

 tains are the birth-places of the vegetable world, but because 

 climate and temperature change with them. The Rhaetian 

 Alps separate Germany from Italy ; on their southern decli- 

 vities we observe Laurels, Pines, Beeches, Cypresses, Jas- 

 mins, and other similar plants, which do not grow on their 

 northern sides. But the temperature on the opposite sides 

 of these Alps is also completely different. 



It must also be added, that the limits of Floras are not defined 

 by mountain tracts alone, but that even in a great extent of le- 

 vel country the Floras have their proper boundaries. Andro- 

 pogon IschtEmum, Asperula cynaiwhica^ glauca^ M. B. Coh- 

 tunculus minimus^ Lycopsis pulla, Bupleurum rotundifolium, 

 Peucedanum officinale, Cnidium silaus, Silcne noct'iflora 

 and conoidea, and Centaurea calcitrapa, seem not to pass be- 

 yond the 52d degree North Lat. into central Germany. At 

 that point, Angelia Archangelica, Lonicera peridymejiuvi, 

 Andromeda polifblia, Arbutus uva ursi, and other forms 

 begin to appear. In completely level countries, the Acer 

 campestrCy Pseudoplatanus, Populus alba, nigia, and Sam- 

 bucus nigra, cease to grow at the 56th degree N. Lat. The 

 Myrtle, Mastick, Oak and Cork tree, the flowering Ash, 

 and the Caper tree, pass not beyond the 44th degree North 

 Lat., whether mountain tracts or level countries occur at this 

 limit. The heights of the Wolga, or Alaunian Mountains of 

 the ancients, are said to be the limit between the eastern and 

 western Floras ; but according to Pansner's recent examina- 

 tion, the entire Wolga heights are only alluvial land, covered 

 with sea sand. Besides, the eastern Flora is seen a great 

 way on this side of the Wolga heights, (Neue Geographische 

 Ephemeriden, b. v. s. 14L) The Weichscl on the north, 

 and the Oder on the south, seem better entitled to be con.^i- 

 dered as the limits of the western and eastern Flora. On the 



