44 



PLANT SUCCESSION AND CROP PRODUCTION 



than the Ohio River. The plateau is better drained than the plain, 

 except near the edge where the drainage is rather poor and there 

 are a number of small lakes, swamps, and prairies. The narrow 

 belt of the Erie Plain along the lake shore is also well drained, 



)etrc 



t^ 



^ 



M I CHIGAN 



Toledo^ 



Sandusky- 



rcievela 





/^' 



\ 



</ 



'X 



3US 



-C 



^' 



Scale 

 10 20 30 40 so Miles 



Fig. 7. Outline map of Ohio showing the physioeraphic divisions. From the geologic Atlas, 

 Columbufl Folio 197. 



but in the broad, nearly level area of the northwestern part, the 

 drainage is somewhat obstructed by glacial deposits. (Fig. 8). 

 These were formerly lakes and swamps. Later, they became prai- 

 rie areas. In recent years, however, drainage and cultivation have 

 effaced these except for the rich humus soil and a few relict plants 

 in undisturbed patches. 



