In order to place phytogeographical regions on a world basis, it is necessary to invoke the zone concept. For example, a botanist who studies the flora of some parts of the USSR, Alaska, Quebec, and Scandinavia recognizes many similarities, if not analogous floras: before considering the local differentiations which distinguish regional floras, he recognizes on first sight the "arctic" aspect. The tendency of phytogeographers, foresters, and biologists in general is to overlook the zonal division of the world from the arctic zone to the tropical zone and consider the regional aspects only. In a zonal division of Quebec, there are thetemperate zone, grossly south of the 50° lat. N.; the subarctic zone, between the 50° and the 55° approximately; thehemiarctic zone, between the 55° and the absolute limit of trees; and finally thearctic zone, north of the 58°. Thehemiarctic zone, described herein, and consisting principally of the habitat commonly called forest–tundra, is not formed of transitional habitats between those of the subarctic zone and those of the arctic zone, but made up of purely arctic patches (from 60 to 90% of the surface) imprisoned in a net of subarctic forest strips. The hemiarctic zone instead of being merely a mixture of arctic and subarctic plants, may be compared then to an "emulsion" of arctic and subarctic habitats. This "mixed" zone, highly convenient for phytogeographical purposes, finds its justification in biological and ciimatological data. For the distinction of the zones, we must not consider only the arborescent flora but all other expressions of life as well. From tentative studies, it is quite evident that a distinction of the zones based on limited floristic aspects,—the aquatic flora for example,—will lead to the same conclusion.