VII. HISTORY OF PLANTS. 
§ 346. 
By the history of Plants we mean, a comprehensive 
view of the influence of climate upon vegetation, of 
the changes which plants most probably have suf-. 
fered during the various revolutions this earth has 
undergone, of their dissemination over the globe, 
of their migrations, and lastly of the manner in 
which nature has provided for their preservation. 
§ 34:7. 
Geographers have divided our globe into different 
zones, circles and degrees. According to this di- 
vision they believe, that under the equator or the 
line, the hottest climate is to be found; under the 
tropics, a warm climate only ; and between the tro- 
pics and the polar circles, a moderate and cold cli- 
mate; that lastly, under the polar circle a frigid 
climate prevails. In general those divisions are 
Aa2 pretty 
