404 GEOGRAPHICAL BOTANY. 



valleys expanded into small plains, and numerous alpine 

 lakes, and is bounded by glaciers and perpetual snow. 

 Catting, ice-cold winds from the east and south-east 

 prevail constantly. Mean temp, of the day in summer 

 = +ll-25, of the night = 7-l; in winter, i. e. 

 during the rainy season, of the day =+ 7'5, of the 

 night ==+ 2 0< 6. The vegetation extends to 15,500', 

 and consists of low Cacti and alpine plants. 



2. Eastern declivity (two regions containing no forests, 

 two wooded). 



a. Puna region (11, 000' 14,000'), or the large un- 

 dulating plateau between the two Cordilleras, and which 

 attains a mean altitude of 12,000'. Sparingly over- 

 grown flats alternate with extensive marshes, lakes, and 

 alpine rivulets. Cold west and south-west winds blow 

 throughout the year, most violently from September to 

 May, with fearful thunderstorms, which occur almost 

 daily during these months. Thus the rainy season com- 

 mences in the opposite half of the year to any one travel- 

 ling from the coast to the interior. The sky is clear from 

 May to September, and the nights very cold ; the tem- 

 perature is altogether very variable ; it frequently varies 

 within twenty-four hours 22 or 25 degrees; not unfre- 

 quently, on these cold heights, we suddenly encounter 

 warm currents of air from the S.S.E., which at times are 

 only from two to three paces in breadth, while in other 

 cases as much as several hundred feet, and which rapidly 

 recur (p. xxiv). Tschudi gives, as approximative mean 

 values of the temperature : Summer (November to April, 

 which period is there incorrectly called the winter), 

 of the night =-f-l-5, of noon=8'75; winter (May 

 to October, there incorrectly called summer), of the night 

 = 6 0< 25, of noon=12 0< l. The vegetation of Puna is 

 poor; Stipa Ichu is abundant; Synantheraceae, Malpi- 

 ghaceae, Leguminosse, Verbenacese, Scrophulariacae, and 

 Solaneae are mentioned. Barley does not ripen at 

 13,050'. 



b. Eastern Sierra (11,000' 8000'), consists of broad, 



