6 American Midland Naturalist Monograph No. 2 



tion within the state, including Primula riiistassinica, Ranunculus rhomboideus, 

 Anemone ludoviciana, and others. Much of the terrain is maturely dissected, 

 and consists of steep, forested slopes. The tops of the plateaus are treeless 

 or only sparsely forested. Along the cliffs of the larger streams there are several 

 northern species of trees, including Pinus strobus, Taxus canadensis, and 

 Betula papyrifera, as well as a number of herbaceous plants. 



MISSISSIPPI border 



The dry western-exposed bluffs of the Mississippi River and of the lower 

 Illinois River have intermittent areas of grassland vegetation containing west- 

 ern prairie species. Sand-prairies are present in the Hancock and Oquawka 

 areas. In a few places sand has been carried by the wind from the river valley 

 to the uplands. Along the northern and central river bluffs the terrain has 

 been deeply eroded, with resultant interruptions of the mantle of loess, and 

 are thus at present not continuously forested. The American beech, Fagus 

 grandifoha, and the tulip tree, Liriodendron tidipijcra, extend northward to 

 Randolph and Jackson counties. The common trees of the northern part of the 

 river bottoms of the Mississippi River are A^er saccharinum, Ulmus americana, 

 Betula nigra, Quercus palustns, and Fraxinus americana. In the southern part 

 of this area Liquidambar styraciflua and Quercus lyrata are common. 



southern division 



The Southern Division is the area of oldest Illinoian Drift. Later deposi- 

 tions of loess with subsequent weathering have complicated the soil profiles. 

 With the exception of the bottomlands, which have a vegetation similar to 

 that of the alluvial soils of the Mississippi Border, the soils throughout the 

 Southern Division are generally poor for plant growth on account of their 

 fine texture and impervious subsoil. Thus they prevent good drainage and 

 aeration, with the result that there is too much water in spring and early 

 summer, and too little in late summer. The principal upland species of woody 

 plants are Quercus palustns, Q. imbricaria, Q. stellata, and Gleditsia triacan- 

 thos. Sassafras albidum and Diospyros virginiana are of not infrequent 

 occurrence. 



WABASH BORDER 



This division includes the bottomlands and bluffs of the Wabash and 

 Ohio rivers, as well as the adjoining upland areas. A great variety of species 

 of ligneous plants is to be found in the forested areas, including Celt is laevi- 

 gata, Acer saccharum, Tilia americana, Quercus borealis, Nyssa aquatica, and 

 Liriodendron tulipijera. Three species of oak, Quercus rubra, Q. prinus, and 

 Q. shumardii, as well as Catalpa speciosa, are characteristic species of this part 

 of the state. The sweet gum, Liquidambar styraciflua, extends northward to 

 Crawford County, and the mistletoe, Phoradcndron flarescens, parasitic prin- 

 cipally on elm and other bottomland trees, is known to occur as far north as 

 Lawrence County. This bottomland vegetation extends many miles up the 

 tributari'es of the Wabash River. 



