4 MB. J. BALL OK THE FLOBA 



4 



by the fact that the valley is to a great extent protected from 

 the influence of the southern currents of the air and ocean, 

 which cool, to an abnormal extent, the sea-board of Peru ; while 

 the increased effect of solar radiation probably makes the heat 

 by day greater than at Lima. In this part of the valley tree- 

 vegetation of a stunted aspect becomes more prominent. Besides 

 Salix Unmioltiana^ which follows the banks of the Eimac, ScJiinus 

 Molle^ and an Acacia (?) with thick trunk and stift' spreading 

 branches, but only 12 or 14 feet in height, are the most con- 

 spicuous forms. 



About 55 miles from Lima, and 7800 feet above the sea, stands 

 San Juan de Matucana, the chief place in the valley. Judging 

 from the fact that many of the characteristic species and even 

 genera of the lower zone disappear above this height, while 



numerous types characteristic of the Andean region are first seen 

 above Matucana, I have fixed on that place as the lower limit, in 

 the Eimac valley, of what I may call the middle ^one of the 

 western Andes. So far as I know, that region is not marked in 

 Peru by the predominance of any vegetable group, such as we 

 find in the Cinchona forests of Columbia. Its natural limits are 

 fixed by a temperate climate, with a very restricted range of the 

 thermometer, combined with occasional though scanty rainfall 

 throughout the year. In this valley its lower limit is marked by 

 that of Heliotropium peruvianum^ which appears to range from 

 about 8000 to 10,000 feet above the sea ; while its upper limit 

 may be indicated by that of the sufFrutescent Calceolarice and of 

 Lupinus paniculatus. 



The most positive conclusion to w^hich I was led by my visit to 

 Chicla was that, so far as regards this part of Peru, the limit of 

 alpine vegetation has been placed by writers on the subject far 

 too low. There can be no serious error as to the heights given in 

 this paper, which are based on the measurements of the railway 

 engineers ; and in departing for Chicla, 12,220 feet above the sea, 

 I fully expected to find myself in the alpine zone of the Andean 

 flora, which Grisebach, on the testimony of Tschudi and other 

 travellers, has placed for Peru and Bolivia between the level of 

 11,508 English feet and the line of perpetual snow. Following - 

 Humboldt, Grisebach places the inferior limit in the Andes of 

 Ecuador and Columbia at the still lower leveJ of 10,872 feet. In 



M 



Grisebach 



