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 be 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 
