PRACTICAL STUDY OF PLANT FORMATIONS. 639 



World-realms. Region in North America. 

 B. Tropical old-world Realm. 



(1) Mexican highland region. 



(2) Tropical American region. 



(These parts of North America 



C. South American Realm. 



are considered as belonging to 

 the Southern Realm.) 

 D. Old Oceanic Realm. 



2. PROVINCES IN NORTH AMERICA. 



(1) Arctic Region, not subdivided. 



(2) Subarctic, or Conifer Region (only those in North America given). 



(c) North American Lake Province (unites on the north with the 

 arctic region and on the south with the Pacific and Atlantic regions 

 of North America). 



The regions of the North American continent come under two realms, 

 as is noted above. Mexican highlands and Central America botanically 

 belong rather with South than with North America. (Three zones are 

 recognized: I, the Algonquin zone, lying between Hudson Bay, Newfound- 

 land and Lake Superior, characterized by Thuja occidentalis and Taxus 

 canadensis; II, Athabasca zone, bounded on the south by a line from 

 Hudson Bay to the Rocky Mountains and characterized by Pinus banksiana, 

 Abies balsamea, Picea nigra, Larix pendula, Picea alba; III, Canadian 

 zone, not clearly delimited, lying southward of the other two and between 

 them, including Manitoba, western Ontario, northern Minnesota, Wiscon- 

 sin and Michigan, characterized by Pinus strobus, Pinus resinosa, and 

 Abies canadensis.) 



(3) Pacific North American Region. (Reaching from the sea to the 

 foot of the Rocky Mountains, and south to the Mexican highlands.) 



(a) Californian coast province (between the Coast Range, and the 

 sea. Characteristic conifers, Sequoia sempervirens, Pinus insignis, 

 Pinus muricata, Pinus tuberculata, Pinus coulteri, Picea bracteata, 

 Torreya calif ornica, Cupressus macnabiana, Cupressus macrocarpa). 



(6) Oregon province. (Including area west of Cascade Mountains.) 

 Four zones are recognized: I, Kaloschen zone, to 52 north latitude, 

 characterized by Thujopsis borealis; II, Douglas zone, to 43 north 

 latitude, characterized by Abies douglasii; III, Umpqua zone, between 

 42 or 43 north latitude, characterized by Cupressus fragrans; IV, 

 Sierra zone, characterized by Pinus lambertiana and Sequoia gigantea 

 (=S. washingtoniana). 



(c) Rocky Mountain province. (Characterized by Pinus flexilis, 

 Pinus monophylla, Larix occidentalis, etc.) 



(d) Colorado province. (Reaching from Cascade to Rocky Moun- 

 tains, open country). 



