26 INTRODUCTION. 



aspect from the slender- twigged beeches and chest- 

 nuts of its temperate regions, or the laurels and fan- 

 palms of its southern shores. 



Viewed in relation to their productions, the gelid 

 regions of the globe are not confined to the circum- 

 polar zone, but extend along the summits of the 

 lofty mountains, following the line of perennial 

 snow, which rises from the level of the sea, in Green- 

 land and Spitzbergen, to the height of 14,000 feet 

 in the Andes. These steril tracts nourish only a few 

 species of plants, although the individuals belonging 

 to them are frequently numerous. In the valleys, 

 and on the southern slopes, no sooner has the return- 

 ing heat of summer melted the snow, than a beau- 

 tiful carpeting of verdure, diversified by flowers of va- 

 rious tints, spreads over the soil, displaying an asto- 

 nishing rapidity of development, while the rocks in 

 many places appear covered with cryptogamic plants. 

 Besides mosses, lichens, and other inferior tribes, mul- 

 titudes of ferns make their appearance. Grasses and 

 creeping dicotyledonous plants are fully matured; 

 and a rich pasturage affords, during the warm season, 

 abundant nourishment to herbivorous animals. Some 

 trees of small size also appear here and there, or even 

 form themselves into thickets and woods. But, in 

 general, the vegetation of these dreary regions, placed 

 on the limits of the habitable earth, is characterized 

 by a paucity of species and a stunted growth. 



Firs and pines, existing in vast numbers, and re- 

 taining a perpetual though gloomy verdure, cha- 

 racterize the transition from the frigid to the northern 

 temperate zone. This last extends from the parallels 

 of 50^ to 40° north latitude, and in its southern 

 borders;, the beech, the lime^ and the chestnut, mingle 



