286 POPULAR GEOGRAPHY OF PLANTS. 



America. In kicking off the prickly coat, these animals 

 often injure themselves so much that they can no longer 

 move about, and at last die. At times when there is a 

 want of water, travellers usually open these juicy plants, 

 which have been called the springs of the desert, with their 

 knives, and thus enable the animals to enjoy the sap with- 

 out danger." 



One more species must be mentioned, which is found on 

 the plateau of Southern Peru, near the limit of vegetation. 

 "On this plateau there are seen mounds a foot or afoot 

 and a half high, of a reddish-yellow colour, which are often 

 mistaken from a distance for crouching deer." The red- 

 dish-yellow tint is produced " by thorns of that colour, two 

 or three inches in length, which colour the whole surface 

 of the mound." 



These varieties of the Cactus have been mentioned more 

 particularly, as being amongst the most peculiar features of 

 the face of Nature on this side of the Andes ; but as we 

 have gradually advanced from the coast towards the interior, 

 the increasing elevation of the mountains, and consequent 

 diminution of heat, are indicated by corresponding changes 

 in the vegetation, from tropical to that of the temperate 

 zones, succeeded next by alpine plants. 



