THE NORTHERN VEGETATION COMPARED, ETC. 147 



in the warmer climates of the temperate zone they alternate more 

 frequently with shrubs or grazing grounds, with smaller plants grow- 

 ing among them. Whatever may be the peculiarities which we 

 observe in the details of this arrangement, there is, nevertheless, a 

 remarkable coincidence between the vegetation of the plains from 

 the middle latitudes northwards, and the vegetation of mountainous 

 districts, especially in the Alps, as we ascend from the plains towards 

 their snowy summits ; the same variety of Amentaceae, Fraxineee, 

 Juglandeae, Acerinae, Pomacese, interspersed with corresponding 

 shrubs, occur in the lower regions, while in the higher the Coniferse 

 come in more extensively, to the almost entire exclusion of the 

 others. 



The correspondence between this ascending forest vegetation, and 

 the distribution of trees over the whole extent of the temperate 

 zone, is so great, that it may be considered as a most positive and 

 universal law. The Juglandeae and various forms of Amentaceae, 

 especially those which produce eatable fruit, as the chestnuts, occur 

 in the lower latitudes under the influence of a more genial climate, 

 and disappear entirely below the parallels where agriculture ceases. 

 So also we find them in the lower regions of mountainous countries. 

 Farther north we have a variety of poplars, oaks, willows, maples, 

 ashes, etc., interspread with pines, which begin to form more 

 continuous forests, till they make room northwards for the almost 

 uniform pine and birch forest, which covers in unbroken continuity 

 the northern countries as far as tree vegetation extends ; and again 

 in a similar succession we observe Amentaceae, Acerinae, &c., &c.,in 

 ascending higher and higher on the slopes of mountains, the conifer- 

 ous trees gaining gradually the ascendency over those with deciduous 

 leaves, until these disappear below the limit of perpetual snow. A 

 more detailed comparison of this resemblance between northern and 

 Alpine vegetation, will show that they agree in almost every respect, 

 and that there are corresponding species under similar circumstances 

 in different parts of the Old and New Worlds, following each other 

 in the same succession from south to north, or from the plains to the 

 mountain summits, modified only by those influences which constitute 

 the contrasting peculiarities of the eastern and western shores of 

 America, Europe and Asia ; but in the main agreeing most extensively 



