Throughout the whole country there were no extensive forests. There were a few tangled thickets among the mountains, where the wild beasts concealed themselves and made their lairs, but this was all. One reason why forests did not spring up was, as is supposed, the custom of the people to burn over the plains every spring, as the Indians were accustomed to do on the American prairies. In the spring the dead grass of the preceding year lay dry and withered, and sometimes closely matted together, on the ground, thus hindering, as the people thought, the fresh grass from growing up. So the people were accustomed, on some spring morning when there was a good breeze blowing, to set it on fire. The fire would run rapidly over the plains, burning up every thing in its way that was above the ground. But the roots of the grass, being below, were safe from it. Very soon afterward the new grass would spring up with great luxuriance. The people thought that the rich verdure which the new grass displayed, and its subsequent rapid growth, were owing simply to the fact that the old dead grass was out of the way. It is now known, however, that the burning of the old grass leaves an ash upon the ground which acts powerfully as a fertilizer, and that the richness of the fresh vegetation is due, in a great measure, to this cause. Such was the country which was inhabited by the wandering pastoral tribes that were now under the sway of Genghis Khan. His dominion had no settled boundaries, for it was a dominion over certain tribes rather than over a certain district of country. Nearly all the tribes composing both the Mongul and the Tartar nations had now submitted to him, though he still had some small wars to wage from time to time with some of the more distant tribes before his authority was fully and finally acknowledged. The history of some of these conflicts will be narrated in the next chapter. CHAPTER XIII. ADVENTURES OF PRINCE KUSHLUK. 1203-1208 Kushluk's escape.--Tukta Bey.--Kashin.--Temujin pursues Tukta Bey and Kushluk.--Retreat to Boyrak's country.----The various tribes submit.--Fall and destruction of Kashin.--Proclamation.--Temujin returns to Karakorom.--Boyrak's precautions.--Great battle.--Boyrak is taken and slain.--Flight of Kushluk and Tukta Bey.--Ardish.--River Irtish.--Tukta Bey's adherents.--Genghis Khan pursues them in winter.--Difficulties of the country.--Death of Tukta Bey.--Kushluk escapes again.--Turkestan.--He is received by Gurkhan.--Presentation of the _shongar_.--Urus Inal.