82 EASY LESSONS IN VEGE TABLE BIOLOGY. 



twenty-four regions of vegetation or natural floras. 

 Each of these is subdivided into zones, and the char- 

 acter of each zone is determined by its elevation 

 above sea-level. A succession of zones is thus ob- 

 tained until the line of perpetual snow sets a limit to 

 vegetable life, We do not find in nature such defi- 

 niteness as our classifications and theories imply, yet 

 there is a general similarity between the flora of any 

 part of the earth and that of a mountain-zone of cor- 

 responding temperature. Thus, similar and often 

 identical plants occur in the lower zones of the mount- 

 ain and in the districts (north or south) having an 

 increase of latitude, and this principle continues until 

 the floras of the snow-line and of the arctic regions 

 generally correspond. Yet, notwithstanding simi- 

 larities, the floras of mountain and of arctic regions 

 show considerable differences. 



7. The base of the mountains near the equator, 

 from the sea-level to about 2,000 feet high, forms the 

 zone of palms and bananas. From this to the height 

 of 4,500 feet is the zone of tree-ferns and figs. In 

 India these are covered by many kinds of peppers, 

 and orchids. In the islands of the Southern Ocean 

 the figs are replaced by tree-like Tfrticacece, and 

 the valuable cinchona-trees characterize the South 

 American region. The zone of myrtles and laurels 

 comes next, extending to 6,000 feet. The predomi- 

 nant trees are those with thick, shining leaves, as 



