23 
FLORA OF NORTH AMERICA. 
BOTANICAL GEOGRAPHY AND LOCALITIES. 
Botanical Geography has lately been much 
attended to since Wildenow, Decandole and 
Humboldt have written upon it. Dr. Picker- 
ing alone has specially written upon that of 
North America, and although I do not admit 
of all his conclusions, nor think his map quite 
correct, yet he has opened the way. 
The Earth is divided into botanical regions, 
where a peculiar growth of trees and plants are 
found ; these regions although sometimes well 
defined in Islands and Physical regions, must 
necessarily blend in large continents near their 
limits. 
Wildenow supposed that groups of moun- 
tains were tfre nucleus of these regions, and 
that the floras expanded 'around ; others think 
that mountains often divide the botanical as 
well as physical regions. In North America 
both seem to be partly the case. 
Decandole had only three botanical regions 
in North America, north of Mexico, the Atlan- 
lic or Apalachian extending to Florida and 
Missouri, 2d the Origonic or the Origon moun- 
tains and plains of the West. 3. the Boreal 
common to boreal Asia and Europe. Picker- 
ing has proved that following the level of the 
land, the Boreal or Canadian extends South 
over the Alleghany mountains, while the Mexi- 
can region extends North into Texas and Ark- 
ansas. 
