ALTERNATION 283 



series of minor mountain zones, forest, alpine grassland or desert, and 

 forest, to say nothing of the foot-hill and timber-line zones of thicket. 



There seems to be no good reason for distinguishing the zones of moun- 

 tains as regions. The term itself is inapplicable, as it has no reference to 

 zonation, and is used much more frequently as a term of general application. 

 Its use tends to obscure also the essential identity of the so-called vertical 

 zones of mountains with the major continental zones, an identity which can 

 not ha insisted upon too strongly. For the sake of clearness, it is important 

 to distinguish all belts of vegetation as zones, though it is evident that these 

 are not all of the same rank. The following division of the vegetation of 

 North America is based upon the fundamental principles of continental sym- 

 metry and the community of continental and mountain zones. 



I. Polar-niveal zone zona polari-nivalis 



II. Arctic-alpine zone zona arctici-alpina 

 Arctic province provincia arctica 

 Alpine province provincia alpina 



III. Boreal-subalpine zone zona boreali-subalpina 



Alaska province provincia alaskana 

 Cordilleran province provincia cordillerana 

 Ontario province provincia ontariensis 



IV. Temperate zone zona temperata 



Atlantic province provincia atlantica 

 Appalachian province provincia appalachiana 

 Nebraska province provincia nebraskensis 

 Utah province provincia utahensis 

 Coast province provincia litoralis 

 Pacific province provincia pacifica 



V. Subtropical zone zona subtropicalis 



Florida province provincia floridana 

 Mexican province provincia mexicana 



VI. Tropical zone zona tropicalis 



Antilles province provincia antilleana 

 Andean province provincia andeana 



ALTERNATION 



342. Concept. The term alternation is used to designate that phenom- 

 enon of vegetation, in which a formation recurs at different places in a 



