The boreal is cold, the austral warm, and the tropical affords conditions of heat and moisture to which the vegetation of the others would be intolerant.
Of these 40 are boreal, 22 austral and 69 tropical.
In the Old World the boreal zone is almost sharply cut off and afforded no means of escape for the Miocene vegetation when the climate became more severe.
He further found that there was an element which he termed boreal in a more intense degree, which amounted to about a fifteenth of the whole flora.
Gray), but till we reach California these are boreal in type.
This takes account of - (I) the ArcticAlpine zone, including all the vegetation of the region bordering on perpetual snow; (2) the Boreal zone, including the temperate lands of North America, Europe and Asia, all of which are substantially alike in botanical character; (3) the Tropical zone, divided sharply into (a) the tropical zone of the New World, and (b) the tropical zone of the Old World, the forms of which differ in a significant degree; (4) the Austral zone, comprising all continental land south of the equator, and sharply divided into three regions the floras of which are strikingly distinct - (a) South American, (b) South African and (c) Australian; (5) the Oceanic, comprising all oceanic islands, the flora of which consists exclusively of forms whose seeds could be drifted undestroyed by ocean currents or carried by birds.
Dr Hart Merriam takes the broad point of view " that the whole of extratropical North America consists of but two primary life regions, a Boreal region, which is circumpolar,;and a Sonoran or Mexican tableland region which is unique."
A remarkable &c, expedition by Baron Toll in 1892 through the regions watered by the Lena, resulted in the collection of material which Afghan- will greatly help to elucidate some of the problems which beset the geological history of the world, proving inter alia the primeval existence of a boreal zone of the Jurassic sea round the North Pole.
Or Boreal branch of the yellow or Mongolic race.
As in European Russia, so in Siberia, three principal zones - the arctic, the boreal and the middle - may be distinguished, and these may be subdivided into several sub-regions.
On the whole, we may say that the arctic and boreal faunas of Europe extend over Siberia, with a few additional species in the Ural and Baraba region - a number of new species also appearing in East Siberia, some spreading along the high plateau and others along the lower plateau from the steppes of the Gobi.
The boreal fauna is, of course, much more abundant; but here also the great bulk of the species, both mammals and birds, are common to Europe and Asia.
Pygmaeus), two bats (the long-eared and the boreal), three species of Vespertilio (V.
North-western corner of the state, which lies in the Boreal zone.
With this animal diet everywhere vegetable substances were mixed, even in the boreal regions.
Except in the boreal areas the breech-clout was nearly universal with men, and the cincture or short petticoat with women.
Fauna.Differences of temperature have produced in North America seven transcontinental life-zones or areas characterized by relative uniformity of both fauna and flora; they are the Arctic, Hudsonian and Canadian, which are divisions of the Boreal Region; the Transition, Upper Austral and Lower Austral, which are divisions of the Austral Region, and the Tropical.
The Transition zone, in which the extreme southern limit of several boreal species overlaps the extreme northern.
In the forest regions north of the lakes the vegetation on the shores of Lake Erie requires a high winter temperature, while the east and north shores of Lake Superior have a boreal vegetation that shows the summer temperature of this enormous water-stretch to be quite low.
California embraces areas of every life-zone of North America: of the boreal, the Hudsonian and Canadian subzones; of the transition, the humid Pacific subzone; of the upper austral, the arid or upper Sonoran subzone; of the lower austral, the arid or lower Sonoran; of the tropical, the " dilute arid " subzone.
The boreal embraces the highest mountain altitudes; the transition belts it on both sides of the continental divide; the upper Sonoran takes in about the eastern half of the plains region east of the mountains, and is represented further by two small valley penetrations from Utah.
There are firs and spruces on the mountains, characteristic of the Boreal zone; pines characteristic of the Transition zone; pinon juniper, greasewood and the universally conspicuous sage-brush, characteristic of the Upper Sonoran zone.