292 cook: vegetation in southern peru 



where reforestation has advanced so far that ample deposits of 

 humus have accumulated. Humus-inhabiting insects of other 

 orders, including the Thysanura and Collembola, are also few. 



absence of palms in tropical forests 



The flora of the valley between San Miguel at 6000 feet and 

 Santa Ana at 3000 feet is distinctly tropical, and large areas are 

 forested, but not with original or virgin growth. That reforesta- 

 tion is still far from complete is shown by the general scarcity 

 and often complete absence of palms. Instead of a normal 

 palm flora, no locality in the Urubamba Valley was found to 

 have more than two species, a large Geonoma and a small 

 Chamaedorea. 



This deficiency seems the more significant because the natural 

 conditions are extremely favorable and the palm flora of the 

 adjacent regions of South America is one of the richest in the 

 world. The original palm flora of this district can not be esti- 

 mated at less than a dozen species, and may have included two 

 or three times that number. But denudation would involve 

 a complete extermination of the palms, and these plants are 

 very slow to return, even after forest conditions have been re- 

 established. 



RECONSTRUCTION OF THE FLORA AND FAUNA 



In view of these indications of prolonged interference with 

 the original conditions of plant and animal life it does not seem 

 reasonable to ascribe the present distribution of the native 

 vegetation entirely to differences of soil, temperature, altitude, 

 or rainfall. An ecological account of the Peruvian flora that 

 ignores the factor of human activity, as in the treatise by Weber- 

 bauer, does not convince. To present an adequate conception 

 of the native flora and its relations with the external conditions 

 would require a process of reconstruction, a careful collecting 

 and piecing together of the parts of the flora and fauna that 

 are left. Then there would need to be a careful comparison 

 with the floras and faunas of neighboring regions that were not 

 occupied and denuded by the ancient civilizations, if such re- 

 gions can be found. This would give a better appreciation of 



