49 



tinuation of the extremely dissected belt described as the western part of 

 the Ozark uplands. Deep loess deposits extend inland to an average of 

 nine miles from the bluffs. Sink-holes pit this region to a greater degree 

 than elsewhere in the state. For the first mile or two from the blufifs, 

 the forests are continuous ; farther inland the ridge tops and stream bot- 

 toms are cleared, and the forests are on the slopes. 



These stands consist of an uneven-aged mixture from which the 

 larger trees have been removed. The transition of species is in about 

 the following order : cucumber-tree and sweet gum do not grow in 

 these uplands north of the Big Muddy ; Mary's River is the upper limit 

 for beech and tulip while black gum goes to the Kaskaskia. Two varia- 

 tions from the mixed hardwood association usual to this region merit 

 mention. Piney Creek, a tributary of Mary's River, has cut a ravine 

 about seventy feet in depth ; and here, on the shallow soils of the slopes, 

 some thirty mature shortleaf pines represent the most northern out- 

 post of this species. (See Plate VIII.) On Rock Castle Creek, some 

 five miles north of Piney Creek, there were formerly specimens of this 

 tree. The shortleaf pine (Pinus cchinafa) is the yellow pine common 

 to the clay soils of the Gulf States but it extends up into southern Mis- 

 souri and southern Illinois. Its occurrence in Union and Randolph coun- 

 ties marks the extreme northern limit of the species. The Piney Creek 

 ravine is also probably the northern limit in the western part of the state 

 for tulip and beech. The second variation is found in the many sink- 

 holes which occur in the uplands near the blufifs. These are generally 

 circular depressions, having a diameter from thirty up to several hundred 

 feet, and a depth often of forty feet. Water may collect and remain 

 in these basins, but ordinarily it is drained ofif through underground 

 streams. Such formations are especially numerous in Monroe county 

 but occur in Randolph, Union, and Hardin counties. The soils, washed 

 in from near-by fields, are fertile. The slopes are often steep and wooded. 

 Tree growth is exceptionally rapid. Black and white oaks commonly 

 predominate, but sycamore, elm, river birch, cherry, and cottonwood are 

 frequent trees in this association. 



North of these Ozark uplands, of the upland belt extending along 

 the Wabash system to Vermilion county, and of the belt extending up 

 the Mississippi to the Kaskaskia, the mixed hardwood forests, in which 

 oak and hickory make up less than 90 per cent of the stand, are in the 

 belt of bluffs bordering the Mississippi and Illinois rivers ; on the unglaci- 

 ated areas of Calhoun and Jo Daviess counties ; on many of the moraines 

 throughout the glaciated area ; and occasionally on the inter-morainal 

 areas where well-drained fertile slopes are forested. 



Such southern species as red and black gums, tulip, cucumber-tree, 

 and beech* drop out, while big-toothed aspen is added in the northern 

 part. White and bur oaks, basswood, black walnut, ash, elm, cherry, and 

 hackberry have a higher percentage in these mixed stands in the north 

 than in the south, while hickory and black oak have a lower percentage 



* SmaH colonies of beech are reported in Lake and Ogle counties. 



