The great variety of productions is to be ascribed essentially to the climate of the countries bordering the Oxus and Yaxartes. It is neither harsh, nor could it exactly be termed mild. On the average it corresponds to the climate of Central Europe, though it must be remarked, that the winter is far more severe on the shores of the Sea of Aral and in the mountainous parts of Khokand, and the summer, on the contrary, much warmer in those districts that lie to the south, and often almost tropical in the immediate neighbourhood of the great sandy deserts. The Oxus is frozen over every winter, from Kerki and Tchardshuy to its mouth; in Kungrad, Khodja Ili, and on the right bank, where the Karakalpaks dwell, the winter is generally very severe; the snow lies often for weeks on the ground, and tempestuous north winds (Ayamudjiz) are not unfrequent. Under such conditions there can be no question of a mild climate, and yet in Khiva I have found the heat unbearable as early as the beginning of June, while in August, near Kerki and Belkh, it was more sultry and oppressive, even in the shade, than is the case in really tropical countries. This great variation in the climate produces corresponding local differences in the vegetation of even a small extent of country. Thus, for instance, the cotton of Yengi Üergendj is far better than that in the more northern districts, and the silk of Hezaresp is considered throughout the Khanat of Khiva to be of first-rate quality. Görlen produces the finest rice, and the finest fruit is found in the environs of Khiva, which lies farther south. In Bokhara and in Khokand we see the same effects produced by the climate, and hence the reason why each of the three Khanats contains, on a comparatively small area, such various and manifold productions, as are usually met with only in larger countries, which lie between several zones.[22] [22] The difference in the harvest time in Turkestan best illustrates the above remark. In Belkh, for instance, and in the neighbourhood of Andkhuj, the harvest is at the beginning of June; in Hezaresp, Khiva, and Karaköl, towards the end of June; in the oasis-countries, in July; in Kungrat, and in the north of Khokand, not before the beginning of August.