158 TRANSACTIONS OF THE ILLINOIS 



tion of the forests in this region, supposing that they ever existed, 

 €an not, with the present knowledge of the subject, be even guessed 

 at. It is, however, fair to assume that forests once existed in a re- 

 gion adapted by climate, rainfall and soil, to produce forests, and 

 that their absence under such conditions must be traced to accidental 

 causes. It is not difficult to understand that the forest, once de- 

 stroyed over such a vast area, could not easily regain possession of 

 the soil protected by an impenetrable covering of sod and subjected 

 to the annual burnings which have occurred down to the present 

 time; Avhile the force of wind, unchecked by any forest barrier, over 

 such an area would, even without the aid of fires, have made the 

 spread of forest growth slow and difficult. The assumption that 

 these eastern prairies may have once been covered with forests is 

 strengthened by the fact that since they have been devoted to agri- 

 culture, and the annual burning has been stopped, trees which were 

 formally confined to the river bottoms have gradually spread to the 

 uplands. Small prairies situated just within the western edge of the 

 forest have entirely disappeared within the memory of persons still 

 living: the oak openings — open forests of large oaks through which 

 the annual fires played without greatly injuring the full-grown 

 trees — once the characteristic feature of those prairies, have dis- 

 appeared. They are replaced by dense forests of oak, which only re- 

 quire protection from fire to spring into existence. In Western 

 Texas the mesquit, forced by annual burning to grow almost en- 

 tirely below the surface of the ground, is, now that the prairie fires 

 are less common and destructive, spreading over what a few years ago 

 was treeless prairie. The prairies then, or the eastern portions of 

 them, situated in the region of abundant rainfall, are fast losing 

 their treeless character, and the forest, protected from fire, is grad- 

 ually gaining in every direction; regions which fifty years ago were 

 treeless outside the river bottoms now contain forests covering ten 

 or even twenty per cent, of their area. These eastern, well-watered 

 prairies must not, however, be confounded with their dry western 

 rim adjoining the plains — the debatable ground between forest and 

 plain — or with the plains themselves. There is no gradual, con- 

 stant spread of forest growth upon the plains. They are treeless, on 

 account of insufficient moisture to develop forest growth; and while 

 trees may, perhaps, if planted, survive during a few years beyond the 

 western limits of the prairie as here laid down, the permanent estab- 

 lishment of forests there does not seem practicable." 



This long quotation tells us, probably as well as it can be told, 

 the reason, so far as known, why a portion of our state is a prairie, as 

 well as some points about the treeless plains that I want to use later. 

 While this does tell us the reason, it does not tell us some ])oints 

 that we want to know. While prairie fires and the tough prairie 

 sod may prevent the spread of oak forests, it is not a reason why 

 they are oak forests instead of forests -of beech_, chestnut, hard 



