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night between 10° and 12°. At the hospital of 

 St. Gothard, situate nearly on the superior limit 

 of the rhododendron of the Alps, the maximum 

 of heat, in the month of August, at noon, in the 

 shade, is usually 12° or 13° ; in the night, at the 

 same season, the air is cooled by the radiation of 

 the soil down to + 1° or — 1*5°. Under the same 

 barometric pressure, consequently at the same 

 height, but thirty degrees of latitude nearer the 

 equator, the befaria of the Silla is often, at 

 noon, in the sun, exposed to a heat of 23° or 

 24°. The greatest nocturnal refrigeration pro- 

 bably never exceeds 7°. We have carefully 

 compared the climate, under the influence of 

 which, at different latitudes, two groups of 

 plants of the same family vegetate at equal dis- 

 tances from the level of the sea ; the results 

 would have been far different, had we compared 

 zones equally distant, either from the perpetual 

 snows, or from the isothermal line of 0° * 



In the little wood of the Pejual, near the 

 purple-flowered befaria grows a heath-leaved 

 hedyotis, eight feet high ; the caparosa ^ which 



* The stratum of air, the mean temperature of which is 

 6°, and which scarcely coincides with the superior limit of 

 perpetual snow, is found in the parallel of the rhododendrons 

 of Switzerland at nine hundred toises ; in the parallel of the 

 befarias of Caraccas, at two thousand seven hundred toises 

 of elevation. 



f Vismia caporosa, (a loranthus clings to this plant, and 

 appropriates to itself the yellow juice of the vismia ;) davallia 



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