The so-called " pampas-grass " (Gynerium argenteum) is not found at all on the dry lands, but in the wet grounds of the south and south-west.
The plains are covered by a formation similar to that of the Argentine pampas and by the alluvial deposits of the present rivers.
Paspalum, is a large tropical genus, most abundant in America, especially on the pampas and campos; many species are good forage plants, and the grain is sometimes used for food.
Evidence of this is to be found in the altitudes of the stations on the Buenos Aires and Pacific railway running a little north of west across the pampas to Mendoza.
The apparently uniform level of the pampas is much broken along its southern margin by the Tandil and Ventana sierras, and by ranges of hills and low mountains in the southern and western parts of the territory of La Pampa.