The vegetation of the dry region of central Asia is remarkable for the great relative number of Chenopodiaceae, _Salicornia_ and other salt plants being common; Polygonaceae also are abundant, leafless forms being of frequent occurrence, which gives the vegetation a very remarkable aspect. Peculiar forms of Leguminosae also prevail, and these with many of the other plants of the southern and drier regions of Siberia, or of the colder regions of the desert tracts of Persia and Afghanistan, extend into Tibet, where the extreme drought and the hot (nearly vertical) sun combine to produce a summer climate not greatly differing from that of the plains of central Asia.
_Fauna._--The zoological provinces of Asia correspond very closely with the botanical. The northern portion of Asia, as far south as the Himalaya, is not zoologically distinct from Europe, and these two areas, with the strip of Africa north of the Atlas, constitute the Palaearctic region of Dr. Sclater, whose zoological primary divisions of the earth have met with the general approval of naturalists. The south-eastern portion of Asia with the adjacent islands of Sumatra, Java, Borneo and the Philippines, form his Indian region. The extreme south-west part of the continent constitutes a separate zoological district, comprising Arabia, Palestine and southern Persia, and reaching, like the hot desert botanical tract, to Baluchistan and Sind, it belongs to what Dr. Sclater calls the Ethiopian region, which extends over Africa, south of the Atlas. Celebes, Papua, and the other islands east of Java beyond Wallace's line fall within the Australian region.
Nearly all the mammals of Europe also occur in northern Asia, where however, the Palaearctic fauna is enriched by numerous additional species. The characteristic groups belong mostly to forms which are restricted to cold and temperate regions. Consequently the Quadrumana, or monkeys, are nearly unrepresented, a single species occurring in Japan, and one or two others in northern China and Tibet. Insectivorous bats are numerous, but the frugivorous division of this order is only represented by a single species in Japan. Carnivora are also numerous, particularly the frequenters of cold climates, such as bears, weasels, wolves and foxes. Of the Insectivora, numerous forms of moles, shrews and hedgehogs prevail. The Rodents are also well represented by various squirrels, mice, and hares. Characteristic forms ot this order in northern Asia are the marmots (_Arctomys_) and the pikas or tailless hares (_Lagomys_). The great order of Ungulata is represented by various forms of sheep, as many as ten or twelve wild species of _Ovis_ being met with in the mountain chains of Asia, and more sparingly by several peculiar forms of antelope, such as the saiga (_Saiga tatarica_) and the _Gazella gutturosa_, or yellow sheep. Coming to the deer, we also meet with characteristic forms in northern Asia, especially those belonging to the typical genus _Cervus_. The musk deer (_Moschus_) is also quite restricted to northern Asia, and is one of its most peculiar types.