RYDBERG: VEGETATIVE LIFE ZONES OF ROCKY MOUNTAINS 497 



12. That the Boreal or Montane Zone is characterized by a pine 

 forest in all three divisions in North America, as well as in Eu- 

 rope, where, however, there are also steppe-lands, especially in 

 Russia. 



13. That the woods of the Subboreal Zone (Transition Zone of 

 Merriam) in all three divisions as well as in Europe are charac- 

 terized by deciduous trees, mainly oaks and other nut-bearing 

 trees, and that this zone is but poorly developed in the Rockies, 

 consisting mostly of chaparrals of scrub oaks, Amelanchier, 

 Cercocarpus, etc. 



14. That the woods of the Upper Austral zones (in the West 

 called Upper Sonoran) in all three divisions in America are mostly 

 made up of evergreens, partly of broad-leaved trees and shrubs, 

 principally live oaks, partly of conifers, as, for instance, pines, 

 junipers, and cypresses. The same is the case in Europe. 



15. That the Lower Sonoran Zone, characterized further south 

 in the middle and the western divisions by the mesquite, creosote 

 bush, giant cactuses, and tree yuccas, is poorly represented in the 

 Rockies, and there only in the caiions and valleys of the Colorado 

 of the West and its tributaries. It corresponds to the Austro- 

 Riparian district of the East with pines, magnolias, cypresses, 

 and live oaks, and to the region of oranges and date palms of 

 the Mediterranean. 



16. That going north or up the mountains we find no sharp lines 

 between the parallel zones, or going east and west between grass- 

 lands or desert and forest, but everywhere we find transition belts 

 or zones of strife between neighboring floras. 



17. That the original Subalpine or Timber Line Zone of Dr. 

 Merriam, which he has abolished, is merely such a transition belt 

 or zone of strife between the Alpine Zone and what I have called 

 the Subalpine Zone, or Dr. Merriam's Hudsonian Zone. 



18. That the Subalpine Zone, or so-called Hudsonian, gradually 

 emerges into the Montane or Canadian Zone. As both contain 

 coniferous woods, the transition is gradual and no distinct transi- 

 tion belt is evident. 



19. That Dr. Merriam's original Transition Zone as designated 

 in his survey of the San Francisco Mountains does not in my 

 opinion correspond to his Transition Zone of the East, viz., the 

 Alleghanian Zone of hardwood forest. The open woods of Pinus 



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