24 NATURAL REGIONS OF ARGENTINA 



hand, the extent of the pasto dulce does not seem to 

 have altered appreciably. The expedition to the Salt 

 Lakes in 1778 found that there were already thistles 

 beyond the line of the ranches, and these are character- 

 istic of the pasto dulce in the Chivilcoy region on the 

 Salado, which was then abandoned to herds of wild 

 cattle. " There was thistle enough to cook," says the 

 journal of the expedition. The difference is connected 

 with the history of colonization in the province of 

 Buenos Aires, where ground was gained only toward 

 the south between 1800 and 1875. Since 1895 the 

 pasto duro has been eliminated by agriculture rather 

 than by the feet of the herds. Hence the advance of 

 the pasto dulce is no longer in a continuous line moving 

 toward the west. It is sporadic, depending upon the 

 construction of new railways which open up the plain 

 to the plough. 1 



Colonization does more than emphasize the indivi- 

 duality of each of the natural regions. It connects 

 together different features, and blends them in a com- 

 plex vital organism which goes on evolving and renewing 

 itself. 



The occupation of the whole of the soil of Argentina 

 by white colonists is quite a recent event. The second 

 half of the nineteenth century was characterized by 

 a rapid territorial expansion, and over more than half 

 the country the expression " new land " must be taken 

 literally. It is only one generation since it was taken 

 from the Indians. There can be no question here 

 of tracing the history of the relations between the 

 white population and the free Indians of the Chaco 

 and the Pampa. The most formidable of these were, 

 in the north, the Abipones and the Tobas. On the 

 Pampa, the foes of the colonists were Indians of Arau- 

 canian descent, Ranqueles, Pehuenches, etc., who 

 came down from the mountains and took to horses. 

 At the close of the eighteenth century the frontier 



' Diario de la expedition de 1778 a las Salinas (Coll. de Angelis, iv.). 



