VEGETATION OF THE INTERIOR VALLEYS (ANDES OF THE 



NORTH-WEST) . 



Descent of Tafi del Voile, going to Santa Maria. The ravine is excavated out of the mass 

 of coarse deposits which forms a fringe between the mountain and the valley. On this permeable 

 soil the vegetation is particularly thin. Cactus. Photograph by the Author. 



FOREST ON THE OUTER SLOPE OF THE SUB-ANDEAN CHAINS. 

 Sierra de San Antonio (Salta province). Perennial foliage, creepers, ferns. 



Photograph by the Author. 

 PLATE IV. To face p. 48. 



