8 INTRODUCTION. 



interruption into the Alps, which throw off the import- 

 ant spur or rib of the Apennines ; thence it divides into 

 the Balkan and Carpathians. We trace the chain next 

 in the Caucasus and the mountains of Armenia with 

 the interruption of the Caspian Sea passing into the 

 Hindoo Coosh and the Himalaya mountains, from 

 whence the chain forks and takes a direction north and 

 south, enclosing like walls the whole delta of China, and 

 thence dips into the eastern ocean. In Africa also, at 

 its widest part, there is a similar back-bone, beginning 

 not far from Sierra Leone, and losing itself in the east 

 in the mountains of Abyssinia ; while in America the 

 mountain-spine trends north and south from the Hud- 

 son's Bay territories, through the Rocky Mountains, un- 

 interruptedly through the Isthmus of Panama, along the 

 Andes to the Straits of Magellan. These vast mountain- 

 systems, with their culminating regions in the Andes, 

 Alps, and Himalayas, and their subsidiary branches or 

 ribs in the Grampians, Doffrefels, Ural, and Atlantic 

 ranges, are clothed on their sides, summits, and elevated 

 plateaus, almost exclusively with cryptogamic vegetation, 

 and enable us to form some conception of the immense 

 altitudinal range of these plants. Then there are whole 

 islands in the Arctic and Antarctic Oceans whose vegeta- 

 tion also is almost entirely cellular. The northern por- 

 tion of Lapland, the continent of Greenland, the large 

 islands of Spitzbergen, Nova Zembla, and Iceland, the 

 extensive territories of the Hudson's Bay Company, the 

 enormous tracts of level land which border the Polar 

 Ocean from the North Cape to Behring's Straits, across 

 the north of Europe and Asia, and from Behring's Straits 



