VEGETATION OF THE INTERIOR VALLEYS (ANDES OF THE 



NORTH-WEST). 



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

 of coarse aeposits which forms a hinge between tht mountain and the VcUey. Un thif pzrmeable 

 soil the Vegetation is pariiculorly thir. 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 I\'. 



To face p. 4^. 



