21-4 THE MOUNTAIN. 



interesting forms within the tree-limit. Sometimes single 

 species occupy extensive surfaces, almost to the exclu- 

 sion of others, their groves stretching in dense and serried 

 ranks over large spaces. 



Again, a number of species grow together, — plants widely 

 separated in botanical affinities, — as, for example, the cone- 

 bearers and deciduous tribes, thus giving all the elements of 

 variety and graceful combination to this order of woods. 

 These mixed growths of trees are of surpassing beauty, 

 some of them exhibiting a grandeur and solemnity found 

 only in the dark recesses of the magnificent forests of the 

 temperate latitudes. They are the great woodlands, possess- 

 ing so much value as reservoirs of timber, for all purposes, 

 and whose importance to man, in every aspect, it is impossi- 

 ble to compute. 



The Alleghany Mountain, in Pennsylvania, in its botani- 

 cal developments through planetary affinities, falls, in its 

 general relationship to the world of vegetable-life, into this 

 belt or zone of geographic distribution of plants. 



The history of this life and its diversity of types, or the 

 " Flora" of the mountain, especially in the department of 

 trees, is one of extreme attraction. 



As the direct and necessary consequence of the geography 

 and geology, or soil and climate of a region, as already shown, 

 the vegetable world unfolds itself by its own fixed and un- 

 alterable laws. Next to topographic distribution of surface, 

 hill, valley, mountain, and stream, ''the vegetable clothing 

 makes the distinctive features of a country, the tree-world, 

 or arborescent vegetation, being especially concerned in im- 

 parting expression and character to surf aces. '^^'^ 



The mixed soils of the different tracts of the Alleghany 

 range, in Pennsylvania, and its mixed climate from elevation 

 above the level of the sea and the medium latitudinal geo- 

 graphic position in the temperate belt of the planet, marks the 

 meeting of separate vegetable classes, and gives great diver- 



* Schouw. 



