cook: vegetation in southern peru 285 



La Ray a, at an elevation of 14,000 feet, down to Santa Ana, at 

 an elevation of 3000 feet, including a visit to the Panticalla 

 Pass and the Lucumayo Valley. The region includes Cuzco, 

 Pisac, Ollantaytambo, and Machu Picchu, the chief centers of 

 the Inca and pre-Inca or Megalithic civilizations, and is of great 

 agricultural and ethnological interest as the original home or 

 place of domestication of numerous species of cultivated plants. 

 In this part of Peru, as in Central America, it apears that 

 the present distribution of the principal types of vegetation is 

 not a natural effect of altitudes, climates, or soils, but an artificial 

 result of an intensive agricultural occupation of the land, extend- 

 ing through a long period of time. If we wish to think of an 

 original condition, a biological background, so to speak, of the 

 primitive agricultural civilization that occupied this region, 

 we must imagine a country well covered with forests. The 

 destruction of forests appears to have been carried much further 

 than in Central America, in many localities to the complete 

 extermination of all forms of arboreal vegetation. The chief 

 considerations that seem to support these conclusions are stated 

 in the following paragraphs. 



BIOLOGICAL CONDITIONS FAVORABLE TO FOREST GROWTH 



Though many districts are now entirely treeless and true 

 forests are found in only a few localities, there appear to be no 

 natural conditions that are definitely unfavorable to arboreal 

 vegetation. Light, heat, and moisture are sufficient to sup- 

 port the growth of trees and there is ample fertility of soil, at 

 the higher elevations as well as in the lower and more tropical 

 valleys. In other words, there seems to be no climatic or biologi- 

 cal factor to preclude the growth of trees on any part of the 

 land surface except the bare rocks and snow fields at the summits 

 of the high cordilleras. 



From the positions of the moraine deposits and the lack of 

 soil accumulations above them it may be inferred that the 

 glaciers have receded in comparatively recent times, perhaps 

 following the destruction of the forests. Some of the moraines 



