With its vast extent and varied climate, Siberia naturally embraces several vegetable zones, differing more from each other even than those of Europe. The southern Steppes have a characteristic and well-marked flora, forming a continuation of that of the Aral, Caspian and Volga plains. The treeless northern _tundras_ also constitute a vegetable domain as sharply defined as the desert itself, while between these two zones of Steppe and _tundra_ the forest region of Europe stretches, with many subdivisions, west and east right across the continent. Of these subdivisions the chief are those of the Ob, Yenisei, Lena, and Amur basins. Beyond the northern _tundras_ and southern Steppes by far the greatest space is occupied by the forest zone. From the Urals to Kamchatka the dense _taiga_, or woodlands are interrupted only by the streams, a few natural glades and some tracts under cultivation. The term _taiga_ is used in a general way for all lands under timber, but east of the Altai it is applied more especially to the moist and spongy region overgrown with tangled roots and thickets, where the _mari_, or peat bogs, and marshes alternate with the _padi_, or narrow ravines. The miners call by this name the wooded mountains where they go in search of auriferous sands. But everywhere the _taiga_ is the same dreary forest, without grass, birds, or insects, gloomy and lifeless, and noiseless but for the soughing of the wind and crackling of the branches. The most common tree in the _taiga_ is the larch, which best resists the winter frost and summer chills. But the Siberian woodlands also include most of the trees common to temperate Europe--the linden, alder, juniper, service, willow, aspen, poplar, birch, cherry, apricot--whose areas are regulated according to the nature of the soil, the elevation or aspect of the land. Towards the south-east, on the Chinese frontier, the birch is encroaching on the indigenous species, and the natives regard this as a sure prognostic of the approaching rule of the "White Tsar." Conflagrations are very frequent in the Siberian forests, caused either by lightning, the woodmen, or hunters, and sometimes spreading over vast spaces till arrested by rivers, lakes or morasses. One of the pleasures of Siberian travelling is the faint odour of the woods burning in the distance. The native flora is extremely rich in berries of every kind, supplying food for men and animals.