Page:Mongolia, the Tangut country, and the solitudes of northern Tibet vol 2 (1876).djvu/303

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VEGETATION DEPENDENT ON RAIN.

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Northwards the character of the desert exhibits a marked change. The bare sand-drifts which cover so vast an expanse of the Urute country soon terminate;[1] and in their place we find a clay soil covered with pebbles. But the topography continues the same; level or slightly undulating plains studded with low hills, now connected in low ridges, now standing in isolated groups, composed of silicious slate, gneiss, and some of the later igneous rocks. There is scarcely any vegetation, and indeed it is also scanty on the plains. Wherever the soil is saline the karmyk and budarhana appear, as in the former tract, and where it improves a little, scrub wormwood and onion are most conspicuous, the latter being characteristic of this region, together with the dirisun and a few more of the Gramineæ composing the flora of the desert. Vegetation, however, is in every part of the Gobi mainly dependent on rains; for no sooner have these fallen, and the sun's rays exerted their influence, than the young plants shoot up with a rapidity which compensates for their long period of inactivity. Green oases quickly manifest themselves where all was desert; the dzeren appears, the loud song of the Mongol lark is heard; the inhabitants remove hither, and the favoured spot teems with life in the midst of surrounding desolation. But how brief a time it lasts! The powerful sun gradually evaporates all

  1. I should mention, however, that sand-drifts occur sporadically in all parts of the Gobi, but are less continuous here than in Ala-shan and the conterminous Urute country.