702 ZONES AND REGIONS [Pt. Ill, Sect. IV 



assumes a peculiar character, termed alpine, which, as it is caused by charac- 

 teristic qualities of tlie mountain climate, has no analogy in lowlands. In 

 mountains we can accordingly distinguish three stages or regions of vegeta- 

 tion, namely : — 



i. The basal region. Vegetation more hygrophilous, but quite as thermo- 

 philous as in the neighbouring lowlands, and like that of moist stations in 

 these lowlands. 



2. The montane region. Vegetation more hygrophilous and less thermo- 

 philous than in the neighbouring lowlands, resembling that of the lowlands 

 in higher latitudes. 



3. The alpine region. Vegetation influenced by the general mountain 

 climate, and without analogy in the lowlands. 



A plant belonging to the basal region will remain unmodified in the low- 

 lands, if the moisture be equivalent to that of its native habitat ; so likewise 

 will a plant from the montane region if in addition the temperature is equiva- 

 lent. An alpine plant does not thrive in the lowlands, or, if it grow there, 

 it partially gives up its alpine habit. 



The regions of vegetation of mountains are not sharply marked off from 

 one another, but, like zones of vegetation, pass gradually one into the other. 

 The lines limiting them must therefore be to a certain extent arbitrary. 

 They also vary according to the mountain in question, because other climatic 

 factors sometimes reinforce the action of the mountain climate, as they do 

 in high latitudes, sometimes weaken it, as they do in lower latitudes. Never- 

 theless all three regions can always be distinguished with certainty, most 

 readily within the tropics, with greatest difficulty in circumpolar districts. 



As the earliest geographical botanists considered temperature alone, they regarded 

 the changes that the vegetation undergoes with increasing altitude as due solely to 

 its fall. Hence they concluded that an equatorial mountain with its summit covered 

 by perpetual snow was, as it were, climatically equivalent to a hemisphere of the 

 earth in miniature, and that it must exhibit corresponding floristic belts. The summit 

 of the mountain clad in ice and snow was to them analogous to one of the poles. 



More recent investigations have proved that the earlier ideas regarding the 

 influence of temperature on the geographical distribution of plants were much too 

 exclusive. Nevertheless the subdivision of mountains in botanical geography into 

 temperature-belts cannot be neglected, as it retains its fundamental significance in 

 regard to many problems concerning the geographical distribution of systematic 

 types. 



Tropical mountains exhibit the following belts of temperature : — 



1. Warm belt with a tropical climate. 



2. Temperate belt. Average temperature about i5°-20°, never below o" C. 



3. Cool belt. Temperature sometimes below o° C. 



4. Cold belt. Temperature usually below o° C. 



I believe it is better to abstain from any general statements regarding the tempera- 

 tures of the highest two belts ; in the first place, because they exhibit great fluctua- 



