AND THE ADJOINING TERRITORY. 205 



a plateau region extending from the base of the Cordillera to 

 the Atlantic coast, the whole of which has been upraised within 

 a very recent geological period, and in which the rivers and 

 minor streams have excavated valleys varying much in depth and 

 breadth. The most remarkable feature in the flora of this region 

 is its extreme poverty. Its components include the plants 

 growing on the dry stony plateaux and those of the comparatively 

 moist and sheltered valleys ; but, putting together all that has 

 been collected and published in Europe, I doubt whether more 

 than 300 indigenous species can be said to be certainly known to 

 grew south of the Eio Colorado. No doubt this number will be 

 largely increased whenever naturalists are able to reach the 

 country at the eastern base of the Cordillera, where Lt. Musters 

 observed many plants not seen by him elsewhere. "With regard, 

 however, to the region now comparatively known, it is certain 

 that the extreme poverty of the flora of such an extensive con- 

 tinental area is a fact quite exceptional. If this be true as to 

 North Patagonia, the case is much stronger as to the southern 

 part of the territory. In the neighbourhood of Santa Cruz 

 Dr. C. Berg was able to collect only 60 species, including in that 

 number a few Cryptogams ; and he notes the rarity of grasses in 

 that district, while in M. Claraz's collection I find 24 species of 

 indigenous grasses, besides 6 others, probably introduced by man. 



The causes of the poverty of the Patagonian flora do not seem 

 to me to have been adequately explained. Prof. Lorentz * is 

 disposed to attach most importance to the uniformity and steri- 

 lity of the soil and the rudeness of the climate. The soil of 

 the plateau is no doubt both very uniform and very sterile, but 

 similar tracts in other parts of the world support a very varied 

 vegetation, and Engler has assigned good reasons for believing 

 that dry soils are in general favourable to the development of 

 new vegetable forms. Further, it may be remarked that the 

 soil of the valleys must exhibit a sufficient degree of variety of 

 moisture, of constituents, and of exposition to favour the develop- 

 ment of many species not yet established there. 



Still less can I admit the severity of the climate as an expla- 

 nation of the poverty of the flora. So far as I know, we have no 

 continuous observations from any place in Patagonia proper; 

 but we cannot suppose the climate of the northern districts to 



* See ' The Argentine Republic,' by Eichard Napp (Buenos Ayres, 1876), 

 Chapter vii. by the late Prof. Lorentz. 



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