Chap. II] 



REGIONS OF VEGETATION 



703 



tions, which, although of the greatest importance in relation to plant-life, have 

 hitherto not been sufficiently determined ; in the second place, because the climate 

 of these belts so far as temperature is concerned undergoes fundamental changes 

 as the distance from the equator increases. 



The temperature-belts of mountains in high latitudes, owing to the increasing 

 differences in seasons as we approach the poles, cannot be equated with the cool 

 and cold belts of tropical mountains. Such a comparison is permissible only when 

 there is not too great a difference in latitude, and has been carried too far by the 

 earlier geographical botanists. 



The connexion between hemispheres and mountains, zones of latitude 

 and zones of altitude, was founded climatically by Humboldt and was 

 extended by him to the whole earth, but Tournefort and Gundelsheimer had 

 previously shown that Ararat exhibits successively from its base upwards 

 an Armenian, a South-European, a French, a Scandinavian, and an Arctic 

 floristic zone. 



The following regions of vegetation were drawn up by Humboldt for 

 the equatorial district of the Andes: — 



HUMBOLDT'S REGIONS OF VEGETATION IN EQUATORIAL MOUNTAINS. 



Height above 

 Sea-level 

 in meters. 



Above 4800 



Mean Temperature 

 for the correspond- 

 ing Altitude 

 (Centigrade^ 



27-5 



24 



19 



16 



13 



4-5 



i-5 



Latitudes with an 

 identical Tempera- 

 ture at Sea-level 



(degrees of 



latitude). 



0-15 



Characteristic Plants. 



Palms and bananas 



15-23 



23-34 

 34-45 



5-58 



58-66 



66- 72 



72-82 



52 -90 



Tree-ferns and figs 



Myrtles and laurels 



Evergreen broad-leaved trees 



Summer-green broad-leaved trees 



Conifers 



Rhododendrons 



Alpine herbs 



Cryptogams (perpetual snow) 



The sagacious conceptions of Humboldt have proved tenable only to 

 a partial extent. His sequence of belts of vegetation in equatorial moun- 

 tains is hardly ever completely represented. For instance, in the tropics the 

 belt of summer-green trees occurs only in certain transitional districts, and 

 that of conifers, if present at all, is usually confused by an admixture of many 

 broad-leaved trees. Finally, the altitude of the limit of trees varies, and is, 

 for instance, much lower on isolated mountains than on mountain chains. 



