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 the 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. 



