106 



THE FERN BULLETIN 



Brown, Monroe, Scott, Lawrence, Jackson, Washing- 

 ton, Clark and Floyd counties. As the name indicates, 

 the hills are knobs or rounded hills, frequently high and 

 steep but generally free from the perpendicular and 

 overhanging cliffs which characterize the Mansfield 

 plateau and limestone plateaus. The highest part of the 

 State is in the vicinity of the "Summit," in Randolph 

 County, about 1,885 feet above sea level. The next 

 highest portion is thought to be the Knob district in 

 Brown County, on the divide between the White and 

 the Ohio rivers. The lowest part of the State is in the 

 southwest part, at the junction of the Wabash and the 

 Ohio rivers. There is very little flood-plain area along 

 the Ohio River in Indiana. It is flanked by the deeply 

 dissected border of the upland plain through which it 

 has cut its deep valley. 



"The broad outcrop of the Mitchell-limestone , 



extending from the northwest central portion of the 

 State, east of south to the Ohio River, is characterized 

 best as having a sink-hole topography. It is a very 

 cavernous region, and the openings from the surface 

 into the caverns are basin-like or funnel-shaped de- 

 pressions known as sink-holes. The many scores of 

 the sink-holes give the area quite a pockmarked ap- 

 pearance." 



Each of these areas contributes to the diversity of 

 the flora. The drift-covered plains contain about 1,000 

 lakes, many marshes and Tamarack bogs, exhibiting 

 the northern bog type of flora. The northern part of 

 the State contains another type of topography not men- 

 tioned in the foregoing sketch, that of the sand dunes 

 around the southern end of Lake Michigan, which has 

 been shown to possess a xerophytic type of flora. In 

 the southern part of the State the Knobs exhibit floras 

 peculiar to both dry barren hills and deep wooded ra- 



