A contrast is presented to this charming vegetation of the Asiatic plains by the dreary Salt Steppes, especially by that portion of the Barabinski Steppe which lies at the base of the Altai Mountains, between Barnaul and the Serpent Mountain, and by the country to the east of the Caspian. Here the social Chenopodiæ, species of Salsola, Atriplex, Salicorniæ, and Halimocnemis crassifolia[DU], cover the clayey soil with patches of verdure. Among the five hundred phanerogamic species which Claus and Göbel collected on the Steppes, Synanthereæ, Chenopodiæ, and Cruciferæ were more numerous than the grasses; the latter constituting only ¹⁄₁₁th of the whole, and the two former ⅐th and ⅑th. In Germany, owing to the alternation of hills and plains, the Glumaceæ (comprising the Gramineæ, Cyperaceæ, and Juncaceæ) constitute ⅐th, the Synanthereæ (Compositæ) ⅛th, and the Cruciferæ ¹⁄₁₈th of all the German Phanerogamic species. In the most northern part of the flat land of Siberia, the extreme limit of tree and shrub vegetation (_Coniferæ_ and _Amentaceæ_) is, according to Admiral Wrangell’s fine map, 67° 15′ north lat., in the districts contiguous to Behring’s Straits, while more to the west, towards the banks of the Lena, it is 71°, which is the parallel of the North Cape of Lapland. The plains bordering on the Polar Sea are the domain of Cryptogamic plants. They are called Tundra (Tuntur in Finnish), and are vast swampy districts, covered partly with a thick mantle of Sphagnum palustre and other Liverworts, and partly with a dry snowy-white carpet of Cenomyce rangiferina (Reindeer-moss), Stereocaulon paschale, and other lichens. “These _Tundra_,” says Admiral Wrangell, in his perilous expedition to the Islands of New Siberia, so rich in fossil wood, “accompanied me to the extremest Arctic coast. Their soil is composed of earth that has been frozen for thousands of years. In the dreary uniformity of the landscape, and surrounded by reindeer, the eye of the traveller rests with pleasure on the smallest patch of green turf that shows itself on a moist spot.” Footnote 18: p. 7.—“_A diversity of causes diminishes the dryness and heat of the New Continent._” I have endeavoured to compress the various causes of the humidity and lesser heat of America into one general category. It will of course be understood, that I can only have reference here to the _general_ hygroscopic condition of the atmosphere, and the temperature of the _whole_ continent; for in considering individual regions, as for instance, the island of Margarita, or the coasts of Cumana and Coro, it will be found that these exhibit an equal degree of dryness and heat with any portion of Africa.