Comparing the Asiatic Steppes with the Pampas of South America, Humboldt does not hesitate to declare that the former are far the richer. "In that part of the Steppes, inhabited by the Kirghiz and the Kalmucks, which I have traversed," he says, "that is to say, from the Don, the Caspian Sea, and the Oural (Jaïk), to the Obi and the Upper Irtysh, near Lake Dsaisang, over a space of forty degrees of longitude, one can never discover, even at the most distant limit, a phenomenon frequent in the Llanos, the Pampas, and the Prairies of America; that horizon vague and boundless as the sea, which seems to support the vault of heaven. Seldom in Asia was the spectacle offered me of even a single side of the horizon. The Steppes are traversed by numerous chains of hills, or covered with forests of conifers. The vegetation of Asia, even in the richest pasturage, is nowhere confined to the families of the _Cyperaceæ_. A great variety prevails there of herbaceous or frutescent plants. In the spring season, small rosaceæ and amygdalaceæ, with rosy or snow-white blossoms--Spiræa, cratægus, prunus spinosa, amygdalus nana--present a graceful appearance. I have elsewhere spoken," he adds, "of the vigorous growth of Synanthers, such as _Suassurea amara_ and _salsa_, the _artemisias_ and blue _centaureas_, which grow profusely in these deserts, and the leguminosæ, which are there represented by different species of astragal, cytisus, and _caragana_. The fritillaria ruthenica, meleagroides, cypripedium, and tulip, delight the eye with the brilliance of their colours."[20] This almost exclusively herbaceous, but abundant and various, vegetation of which Humboldt speaks, is conspicuous in the spring, in the least favoured Steppes, after the rainy season. But it is there of a brief life. In the month of June the heat grows intense, and the dryness excessive. Then every herb perishes, cut down by the sun's keen-smiting rays, like the Greeks before Troy by the arrows of Apollo. "Bent was his bow, the Grecian hearts to wound; Fierce as he moved, his silver shafts resound."[21] The dust is whirled off the ground by the wind, and swept about in revolving tornados. The Steppes situated in a comparatively low latitude thus alternately assume the most discordant aspects. In winter the heavy rains inundate them, and transform them into impracticable marshes; spring clothes them with a thick carpet of grasses and other herbaceous plants, so that they reveal to the eye leagues upon leagues of delightful sward cropped by numerous flocks. In summer they undergo a third metamorphosis, and are converted into parched and sun-scathed deserts like those of Nubia or Arabia.