34 SOUTH AMERICA— THE ANDES REGIONS. 



or the solar heat. Boussingault found a saxifrage growing at a height of 

 15,770 feet on Chiniborazo, while mosses and lichens have been gathered on the 

 same mountain at altitudes of 16,500, 17,000, and even 17,350 feet. 



On the slopes of the mountains and along the main ranges the different 

 floras follow in succession one above the other — at their base tropical plants, 

 hio-her np those of the temperate zone, and towards the summits an alj)ine or 

 glacial vegetation. Thus the Andes and the other South American highlands 

 contribute by their superimposed climates to the great variety of species 

 characteristic of this continent. In Europe, where most of the ranges are 

 disposed in the direction from east to west, the various vegetable forms spread 

 freely in the same direction from one end of the continent to the other. But not 

 so in South America, where the [)lants of the east are abruptly arrested by the 

 barrier of the Cordilleras, while on the opposite side, even under the same lati- 

 tude, other forms have been developed, analogous, but still distinct enough to 

 constitute an independent flora. 



Lastly, the oceanic archipelagoes of the Galapagos and Juan Fernandez 

 are distinguished amongst all marine lands for the original character of their 

 floras, forming in this respect little worlds apart. 



By keeping in view the chief contrasts between the floras diversely 

 intermingled at the points of transition from zone to zone. South America 

 may be divided into eight great botanical domains, to which must be added 

 the archipelagoes, as forming so many different provinces. The Falkland 

 Islands, however, resemble Tierra del Fuego in their herbaceous and scrubby 

 growths, and in the general aspect of their vegetation. 



According to 0. Drude* the eight divisions are as under : — 



Tropical Zone. — 1. Evergreen virgin forests; rains throughout the year, or 

 for not less than nine months. 



2. Forests and savannas intermingled ; dry season of over three months. 



3. Tropical flora of the uplands. 



Temperate Zone. — 4. Evergreen forests with palms and pines ; summer rains 

 from December to March. 



5. Evergreen shrubs ; few or no trees ; no palms ; winter rains. 



6. Evergreen trees, with deciduous leaves; bush; pine forests; no palms; 

 rains throughout the j^ear. 



7. Prairies, steppes, and deserts ; great variations of temperature ; slight 

 rainfall. 



Frigid Zone in the mtifh and on the uplands. — 8. Impoverished arborescent 

 vegetation. 



Thanks to its extremely diversified flora. South America has, during the last 

 four centuries, given to the civilised world more plants useful for alimentary, 

 medicinal, and industrial purposes than any other division of the globe. The 

 potato, which has become the staple food of so many millions of human beings, is 

 of South American origin, growing wild at various altitudes in the region of the 



* Berghaus's Physikalischer Atlas. 



