RECOGNITION OF THE CHARACTER OF SOILS. 515 



linden, the wild cherry and the ash ; the latter two also usually 

 appear in the bottoms of the streams and on the slopes ad- 

 jacent, together with the walnut and butternut, and in the 

 lowest ground the sycamore. 



The tree growth of the Loess belt bordering the Ohio and 

 Mississippi, so far as climatic differences permit, agrees almost 

 precisely with that described in the corresponding portions of 

 Mississippi and Tennessee. The change from the oak and 

 hickory growth covering the yellow-loam uplands toward the 

 more calcareous area is evidenced by the appearance of large 

 sturdy trees of sassafras, together with the linden and sugar 

 maple. Descending from the " bluff " toward the rich bottom- 

 prairie with its black, heavy soil, we at once encounter the 

 familiar indices of the more highly calcareous land, viz., the 

 honey locust, clumps of crab apple and red haw, with hack- 

 berry, Kentucky coffee tree and mulberry on the lower ground ; 

 In late summer and during autumn, a tall growth of the iron 

 weed (I 7 ernonia), several Eupatoriwns (E. pcrfoliatum and 

 pur pur cum, the white and the purple boneset) and of the blue- 

 spiked Verbena are very characteristic, as are also several spe- 

 cies of Cassia (Carolina coffee, etc.,) and the swamp rose-mal- 

 low. 



Upland and Lowland ]*cgctation in tlic Arid and Humid 

 Regions. In the humid countries there is commonly a marked 

 difference between the vegetation of the uplands and lowlands, 

 arising not merely from the difference in the moisture supply, 

 but evidently of a specific nature. When we discuss the char- 

 acteristic plants in detail, it becomes obvious that it is lime 

 vegetation that, in most cases, forms the characteristic dif- 

 ferences l>etween upland and lowland forest growth ; a nat- 

 ural consequence of the leach ing-down of the lime from the 

 higher land to the lower levels. By way of counter-proof we 

 find that when the uplands themselves are of a calcareous 

 nature, a part at least of the lowland flora ascends into 

 them. As prominent examples may be mentioned the Tulip 

 tree (Liriodcndron), black walnut, ash, Kentucky coffee tree, 

 Hercules' club, etc., which are lowland trees over the greater 

 part of their area of occurrence; but in the loess or Cane hills 

 bordering the Mississippi and its larger tributaries, as well as 

 in the limestone regions of the southwestern and western states, 



