22 



BULLETIN 117, UNITED STATES NATIONAL MUSEUM. 



exactly on the parting of the great forest of the Amazonian Basin and the grassland of 

 the Andean pampa region. The forest at this place stops as abruptly as if cut by a 



knife, quite as sharply as a hedge row on the borders 

 of a lawn; long tongues of forests in places, however, 

 follow up the creek margins or ascend favorite slopes 

 to a thousand feet beyond the general forest limits. 

 There is no dwarfing of trees or diminution in their 

 numbers on the borders. A variety of trees gi-ew at the 

 timber-line edge. There were shaggy barked Acaena 

 ochreata trees with drooping masses of gray-green foli- 

 age, small, erect Gynoxys trees with their dome-shaped 

 crowns adorned by golden composite blossoms, a white- 

 barked Melastomataceous tree of the genus Miconia 

 towered above all with its spidery branches spreading 

 in every direction. A small, stout-trunked fern, an 

 arborescent Lomaria, was a constant feature of the 

 forest edge. Bamboo grass {Chusqnea quila) in some 

 places intertwined its light green stalks with the 

 trees, but it was chiefly along the borders of streams 

 and on swampy soil that it flourished. Mosses and 

 lichens of many colors and sorts smothered the tree 

 trunks and branches, making them in appearance 

 many times their actual size. The gray-beard lichen 

 was the prevalent one on the terminal parts of the 

 branches, and another, a deep black species, confined 

 its affections to the trunks and larger branches. Be- 

 yond the forest a luxiu-iant growth of grass covered the 

 mountain slopes, mingled with which, but in close 

 proximity, were small huckleberry bushes, Baccharis 

 bushes and a few tall herbs. Cedrobamba climati- 

 cally was damp and cold. It was at the edge of a 

 more or less permanent fog bank, the limits of which 

 seemed to coincide with that of the forest. 



Rain in great quatities apparently does not fall here, 

 but the region is constantly bathed in cold mists. 

 The nights are cold but seldom bitter, the daily ex- 

 tremes of temperature being considerably less than 

 in the drier region farther inland of equal elevation. 



Heller Expedition, May 23-June 15, 1915; 

 54 specimens of 30 species. 



Santa Ana (altitude 3,480 feet, arid Tropi- 

 cal Zone). — The valley of Santa Ana is a 

 semi-arid tropical pocket shut off from the 

 heavy rainfall of the true Amazonian region 

 by the rang-e of the Andes which lies to the 

 eastward of it. Bowman ® presents a dia- 

 gram (here reproduced) of the climate of 

 the eastern slope of the Andes and writing 

 of Santa Ana says : 



It will be seen that the front range of the mountains 

 is high enough to shut off a great deal of rainfall. The 



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» The Andes ol Southern Peru, p. 79. 



