THE NORTHERN VEGETATION COMPARED, ETC. 149 



vegetation stretching over a widely-expanded horizon. So that not- 

 withstanding the correspondence of species, we have in the first case, 

 in the Alps, a rapid succession of highly-diversified vegetation, whilst 

 in the other case, in northern latitudes, we have a monotonous uni- 

 formity over extensive tracts of land, although the elements of the 

 picture are the same. But it is a picture seen in a different perspec- 

 tive : in one case we have a simple vertical profile, which in the 

 other case is drawn out into disproportionate horizontal dimensions ; 

 like the far-reaching shade of a steeple cast under the light of the 

 setting sun, which may change all proportions, and destroy all resem- 

 blance between the shade and the object itself, simply because it is 

 so much elongated. Fantastic images presented at various distances 

 before a light falling at various angles, may prepare us to understand 

 these different aspects of the landscape, be it a wooded plain 

 along a gentle slope, or a forest along a more abrupt mountain chain. 



There is another feature in the geographical distribution of organ- 

 ized beings which deserves to be particularly noticed, and which con- 

 tributes to increase the diversity of aspect of vegetation in any given 

 part of the world. There are in all continents remarkable differ- 

 ences between the vegetation of the shores of a continent, east 

 and west, within the same latitude or the same isothermal line. The 

 forests of the Atlantic and Pacific coasts of temperate America 

 are not altogether composed of the same plants ; we remark that in 

 the East there will be a tendency in the different families to develop 

 in different proportions, and perhaps with the addition or disappear- 

 ance of one or two peculiar types ; for instance, the walnut family 

 contains several more representatives on the eastern side of the con- 

 tinent than on the western, and they prosper here in latitudes where 

 in Europe there is only one introduced species of that family growing 

 wild. Again, we find Liquidambar on the American side of the 

 Atlantic, which has no representative either on the Pacific coast, 

 or in Europe. This comparison might be traced farther, and we 

 should see the same correlation even among the shrubs. 



But these indications will be sufficient for my object, which is to 

 show that, although there is an intimate correlation between climate 

 and vegetation, the temperature and other influences which consti- 

 tute climate do not reveal the whole amount of causes which produce 



