THE EQUATORIAL ZONE. 289 



the highest mountains in Europe.* These immense pla- 

 teaux may be described as high valleys, connecting the 

 two lines of the Andes, which run like a double chain 

 from the northern extremity of South America to nearly 

 four degrees south of the equator, where the inner chain 

 ceases, and the plateau which united it to the coast 

 Andes becomes lower. Throughout these level regions we 

 may travel whole days and weeks without meeting with a 

 single tree growing spontaneously ; the nearest approach to 

 such a thing (and this only at immense intervals) is an oc- 

 casional miserable-looking shrub, called a Polylepis (one of 

 the Sanguisorb tribe) ; or, more rarely still, the stunted 

 trunk of another shrub, called a Biittneria, of the Natural 

 Order Calycantkacece, which in structure comes nearer to 

 the Rose tribe than to any other ; it has square stems, with 

 opposite simple leaves, and chocolate-colonred flowers of 

 aromatic fragrance. 



But even here our path may be sometimes said to be 

 strewed with flowers, for the ground is often covered like a 

 carpet with little Verbenas, in the same sort of way as the 



* One, which occurs between Pelechuco and the Lake of Titicaca, lies at 

 an elevation which is about 164 feet higher than the summit of Mont Blanc. 

 The thermometer there sometimes stands at 14 Fahr., even in the sunshine. 



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