A CHAT ABOUT PLANTS. 149 



the greatest size combined with the greatest variety, the 

 most graceful proportions by the side of the most gro- 

 tesque forms, decked with every possible combination of 

 brilliant coloring. Here also and here alone are found 

 truly primeval forests, impenetrable to man and beast, 

 from the luxuriance of thickly interwoven creepers above 

 and the density of a ligneous undergrowth, through which 

 not a ray of light can penetrate. 



As the distribution of plants in zones depends almost 

 exclusively on the amount of heat which they require for 

 their development, we find that the succession of plants 

 from the foot of mountains upwards to their summit, is 

 nearly the same as that from the middle latitudes to the 

 poles. For heat decreases in the same proportion by 

 height above the level of the sea as by latitude ; and 

 the horizontal zones on a mountain's side present the same 

 variety of plants, as the great zones mentioned, only in 

 a much smaller space, as we feel the temperature of the 

 atmosphere diminish more rapidly in ascending a lofty 

 mountain, than in travelling from the tropics to the poles. 

 Hence the same peculiar plants are found in the arctic 

 zone, and on the highest mountains which reach the line 

 of perpetual snow ; the same humble but beautiful flowers 

 blossom in Spitzbergen, or on the icy shores of Victoria 

 Land, and on the desolate cliffs of the Andes, the Alps 

 and the snow-covered heights of the Himalaya. Even un- 

 der the tropics, the evergreens of the north appear again : 

 the most elevated regions of Peru, and the lofty plains 

 of Asiatic mountains are covered with superb forests of 

 that noble tree of which the poet says : 



