IW IT, A NT \.\VK OK A I, A HAM A. 



mean trinjtcralun' (liiriiiLT :i l»rirt' jH-rind coxciiiij^" the lioltcst |»art ol 

 the ycai'. 



Tlu'Sf hoiindarics were IOiiikI (<» confonii with the liinils of dis- 

 t ril)ii(i(Hi ol" species as arrived al l»y lield olisei\at ioii>. 1 )in'ei'eiico.s 

 ill moisture, the factor next in importuiice to heat in the distril»ution 

 of life — on this continent most potent in its inlliience fi'om east to 

 west — detei'miiie the disti-iluition of animals and plants within dis- 

 tinct areas of tiiese life zones. 



Based on thesi> principles Dr. McM'i'iain recoefiii/es in the North 

 American continent three primary divisions or reeions Hoi'eal. Aus- 

 tral, and Tropical -and se\-en transcontinental zones. His (dassifica- 

 tion is as follows: 



I Arctic or Arctic- Allelic '/.(inc. 

 Hnil>i(»naii Zone. 

 CaiKidian Zone. 



Alloghcnian Area. 



' Transition Zone { A ri< 1 Transition A rca. 



Pacilic Coast Transition Area. 



AisTKAL Region. 



r. 1,1'/ /Carolinian Area. 



i nucr . iistnti Zone < ,t , , . 



'' \ Up])er Sonoran Area. 



r i 4 I V / Austrorii)arian Area. 



Lower A iixtral Zone % , ,,' . 



\ l.,o\ver .Sonoran Area. 



T, r, f Humid Tropical. 



lUOlMCAl. KE(iION < . • 1 rn • ^ 1 



\Arid Tropical. 



BOREAL REGION. 



This, as seen in th(> table, presents three ti(dts or natural suhdivi- 

 sions. 



AKCTie OK AKCTK-ALJ'INE ZONE. 



This division, the first of the three, extends from the limit of tree 

 growtli to the polar lands. The greatest portion is covered with eternal 

 snow and ic(>, and farther south it intdudes the sununits of the moun- 

 tains reaching- al)ove the line of arboreal growth, subject to the same 

 conditions. This zone is recognized by some writers as the hyper- 

 boreal region, and as the realm of mosses and saxifrages. 



nUDSONlAN ZONK. 



The second, namely, the Hudsonian or subarctic zone, embrac^es the 

 most northern part of the American forest. Its spruces, firs, and 

 most of its l)irches and aspens extend from the shores of La])rador to 

 Alaska. This zone is spoken of as the Northern Forest or Lacustrian 

 Forest of the North. 



CANADIAN' ZO.VE. 



This is the third sul)division, or the second of the northern belts 

 of cone-bearing trees. In this zone pines, spruces, firs, and hendocks 

 outnumber the deciduous forest growth. In the southern and warmer 

 parts of this belt the cultivation of the hardier cereals — oats, r3^e, 

 barley — is possible, and potatoes and other root crops succeed. 



