1008.] 



LIFE ZONES ARCTIC. 



51 



mota caligata)^ and lemmings of the genus Lemmus. The charac- 

 teristic birds inchide the white-tailed ptarmigan {Lagopus leucurus). 

 the jDipit (Antlms riihescens) and probably the rosy finch (Lea- 

 costicte tephrocotis) . 



HUDSONIAN ZONE. 



South of the Arctic zone lies the Hudsonian, a belt of more or 

 less stunted timber. In the Mackenzie region it has no strictly 

 characteristic mammals, though the range of a red-backed vole {E vo- 

 tomys dct'wsoni) is practically confined within its limits. Most of 

 the woodland mammals necessarily have their northern limit within 

 this zone. Such comprise the following: Rangifer caribou^ Alces, 

 Sciuropteims^ Sciurus^ Castor, E cotomys. Fiber ^ Erethizon^ Lepiis 

 americanxis^ Lynx^ Lutra^ Lntreola^ Mustela^ and others. Among 

 birds, the great gray owl {Scotiaptex nehulositm) ^ hawk owl {Siirnia 

 ulula caparocli) ^ pine grosbeak {Pinicola e. leucura), and tree spar- 

 row {SpizeUa monticola) breed principally within it. Its trees are 

 those of the Canadian zone, though the Banksian pine {Pimis dicari- 

 cata) and balsam poplar (Popidiis balsamifera) barely enter its 

 borders. Its shrubs are mainl}^ species that overlap from the ad- 

 joining zones. Among those which seem to reach their greatest per- 

 fection in the Hudsonian may be mentioned Empetrum nigrum. 

 Ledum palustre^ V accinium idiginosum^ Vitisidcea vitisidma^ Oxy- 

 cocciis oxycocciis^ and Betida nana. 



The northern limit of the Hudsonian, being the line dividing it 

 from the Arctic, has just been defined; its southern boundary remains 

 to be indicated. On the southwest shores of Hudson Bay- the zone 

 occupies a strip about 200 miles in width. Thence its southern 

 boundary extends inland, passing through Athabaska Lake, and then 

 bending northward crosses Great Slave Lake just east of the mouth 

 of Slave River. Practically all of the northern shore of Great Slave 

 Lake lies within its limits. Beyond here its lower boundary is very 

 uncertain. It is bounded by a strip of Canadian country, probably 

 only a few miles in width, extending northward along the Mackenzie. 

 This southern influence ceases to be effective near the mouth of Bear 

 River, and the southern limit of the Hudsonian may be considered to 

 cross the Mackenzie near latitude 65°. Thence it bends again south- 

 ward, following the western border of the Canadian strip. Here, as 

 on the eastern side, the position of the boundary is unknown, but 

 because of the great altitude of most of the country west of the 

 Mackenzie and north of the Liard the Canadian zone influence can not 

 extend far from the river and the Hudsonian must cover nearly the 



