OF PLANTS. 247 



Pine. A zone of Conifers shields us from the sun's rays 

 up to a height of 6,000 feet, then the vegetation suddenly 

 becomes low, from humble bushes it passes into a Flora 

 which bears all the characters of the Alpine plants, till 

 finally the naked rock sets a limit to all organic life, and 

 no snow and ice bedeck the summit of the mountain, 

 only because its height of 12,236 feet does not, in a 

 position so near the tropics, extend up to the region of 

 eternal snow. Counting by the limits of vegetation, we 

 have re-surveyed in a few hours' climb, the wide way from 

 Spitzbergen to the Canaries, an extent of more than fifty 

 degrees of latitude. 



In the whole way, downwards toward the south and 

 upwards toward the summit of Teyde, vegetation changed 

 conformably with the climatal conditions, and we can 

 almost account for the observed distribution of plants by 

 the mere increase and diminution of heat. If we extend 

 our researches farther, we can even name particular plants 

 which are peculiar to particular northern latitudes, and in 

 lower latitudes again regularly recur at particular heights 

 on the mountains. Nevertheless, this case is comparatively 

 of rare occurrence, and we are finally compelled to refer 

 instead to another influence, less or scarcely at all under- 

 stood. When we find places in the tropical mountains, 

 which, in reference to moisture and temperature, as well as 

 to the constitution of the soil, exactly correspond to certain 

 places in northern latitudes, and which in spite of this 

 support a vegetation, which is, indeed, similar in general 

 character, but wholly distinct in the genera and species, 

 nay, when we notice that the agreement between northern 

 latitudes and elevation above the level of the sea in 

 southern latitudes, can be superficially demonstrated only up 

 to a height of about 6,000 feet, we are thereby directed to 



