13G JOURNAL OF THE ARNOLD AIIBORETLM [vol. ir 



Oak (Qucrnts imbricaria). Flowering Dogwood {Cornus florida), anJ 

 \Vhilc Asli {Fraxinus americana) are frequent; and in the more open 

 places several species of Red Haws, Crab Apples and Plums are found, 

 together with Sassafras, Persimmon, Blackberry, Climbing Rose and 

 Simimer Grape. Along the rocky margins and beds of some of the streams 

 grow the Silky Willow, Smooth Alder {Alnus rugom). Silky Dogwood 

 {Cornus amomum), Winterbcrry {Ilex verticillata), and Shrubby St. John's 

 Wort (Hypericum prollficum). The Ohio Buckeye {Acsculus glabra) grows 

 abundantly in rich alluvial ground along a branch of the Cache in John- 

 son County. 



On tlie western side, paralleling the Mississipj)! River and extending 

 through th<^ northern half of Alexander and across Union County, is a 

 mirrovv area of Devonian rocks, consisting of compact limestone with 

 considerable interbedded cliert. Near Thebes the bold bluffs of this for- 

 mation approach the river, but further north arc separated from it by a 

 wide bottom. The surface of the uplands here is in places strewn with 

 angular fragments of residual chert, and affords conditions more closely 

 resembling typical sections of the Ozarks in Missouri tlian any other part 

 of sontliern Illinois. In the vicinity of Alto Pass the country is quite 

 rugged, with Mississi])pian sandstone exposed in picturesque bluffs and 

 huge residual masses about the village. The -altitude at the M. & O. 

 depot is 74G feet, and hills in the vicinity must be considerably higlier, 

 A few miles to the southwest is a much broken area, locally known as 

 tiic *'Pine Hills." On the points of some of the highest ridges the Short- 

 leaved Pine (PhiiLs cchinaia) grows, though in no great abundance. It 

 is evidently an oul])ost of the large colonics of this species found on simi- 

 lar rocky ridges in sections of the Missouri Ozarks. The surface of the 

 ujdands in the Pine hills is tliickly covered with chert fragments; Oaks 



and 



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nafiTig. The aciJ cluiraclcr of Ihe soil and the Ozarkan lype of the flora 

 are also emphasized hy the presence of such Ericaccous plants as Rhudo- 

 dcndrun rnscum, Vacciniuin virgatum tencUum and V. arborcum, the 

 first of which, at least, has been found nowhere else in southern Illinois. 

 At the other extremity of the Ozark Ridge, bordering the Ohio River, 

 in Pope aiul Hardin Counties, limestone of the Mississippian series is 

 the prevailing country rock over a considerable area. The surface is 

 quite broken, and sink-holes and caves abound in many places. Iligl 



^■' 



picturesque bluffs appear along the Ohio and smaller streams, and out- 

 crops and bare ledges occur on the steep slopes and tops of some of the 

 hills. Fluorspar with ores of lead and zinc is mined from the St. Louis 

 limestt)ne, and is becoming the basis of an important industry. Tiie 

 flora here is not renuirkably different from that of the central sandstone 

 portion of the ridge, but In places on the limestone hills stunted Cedar 

 bushes and various species of Red Haws, Tlums and other small trees 

 and shrubs form extensive thickets, and the geuus Crataegus is reprc- 



