182 LAKE SUPERIOR. 



and in the higher parts, CratiTSgus Chamgemespilus Z., Azalea pro- 

 cumbens i., Empetrum nigrum Z., Acer pseudoplatanus L. 



Above all these we meet already in the Jura the Rhododendrons 

 and the Salix herbacea, which belong ti-uly to the alpine flora char- 

 acterized by all those handsome plants covered with a light cotton 

 down, which we find along the margin of the glaciers in the Alps, 

 and as high as the uppermost limit where all vegetation ceases some- 

 what suddenly, at a level of about 8,000 feet above the level of the 

 sea. 



Trees of the Lake Superior Region. 



We may place at about 40° northern latitude the zone of vegeta- 

 tion, which in America corresponds to the upper limit of the cultiva- 

 tion of the vine, as we observe it on the banks of the Swiss lakes. 

 At about this latitude the family of the Magnoliacese dies out, though 

 we may still meet the Magnolia glauca in the swamps, as far as the 

 43° N. lat., and though the tulip tree still flourishes there. This is 

 also the northern limit of the Anonace^e, Melastomacege, Cactaceae, 

 Santalacese, and Liquidambar ; and though in Europe we have no 

 representatives of these families, it is easy to perceive, on reflecting 

 upon the examples just mentioned, that the limits of vegetation under 

 consideration are natural, and correspond to each other, though 

 characterized in the two continents by different plants. Again, the 

 numerous species of wild vines which America produces, although 

 they do not extend farther northwards than the cultivation of the 

 vine in Europe, yet prosper on tliis continent in a colder climate. 



The State of Massachusetts, with its long arm stretched into the 

 ocean eastwards, or rather the region extending westward under the 

 same parallel through the State of New York, forms a natural limit 

 between the vegetation of the warm temperate zone, and that of the 

 cold temperate zone, whose forests G. B. Emerson, Esq., has so well 

 described in his admirable Report upon the Trees and Shrubs of 

 Massachusetts. With this book, we may become well acquainted 

 with the arborescent vegetation of the zone which corresponds to the 

 horizon of oaks and shrubs in the Jura ; so that I need not enumer- 

 ate these characteristic species. Not only is this also the northern 

 limit of the culture of fruit trees, but this zone is equally remarkable 

 for the great variety of elegant shrubs which occur particularly 



