150 SOUTH AMERICA 



evergreen. Tree ferns are always present in the gullies. 

 On the more porous soils the forest is reduced to a tall 

 and crowded deciduous jungle, among which is found 

 the yerba-mate', somewhat resembling a broad-leaved 

 laurel. 



With the decrease of precipitation towards the west, 

 the forest, without changing its density and character, 



FIG. 49. Paraguayan Forest near Guayra Falls. 



remains limited to the rises and undulations. Tall 

 grassy campos, sometimes studded with palms or 

 scattered thickets, intermingle more and more with it, 

 finally predominating on the lower alluvial levels which 

 gradually lead to the marginal swamps of the river Para- 

 guay. Each of the numerous rivers throws up at flood 

 time a double high bank clad with a varied and thick 



