320 



General Botany 



Fig. 197. Oak-hickory forest in central Illinois. In this region the deciduous forest 

 formation and the prairies meet, the forests occupying the slopes and stream valleys, and 

 the prairies the flat uplands. 



forest, varying from 70 per cent in the east to 50 per cent at the 

 western edge, where the forest extends along the rivers into the 

 prairies and plains. 



Toward the north and on mountain slopes, northern conifers 

 like the white pine and hemlock occupy considerable areas, or 

 they may be mixed with the broadleafed species. Southward, 

 on cliffs, sandy plains, and shallow soils, many trees, like the 

 shortleafed pine, pitch pine, and scrub pine, occupy pioneer 

 habitats. On the Piedmont plateau region the shortleafed and 

 longleafed pine are mixed with oak-hickory forests. The uplands 

 immediately west of the Mississippi River were originally covered 

 by oak and hickory forests, shading into walnut, elm, and beech 

 of magnificent proportions on the more fertile soils. Here the 

 shortleafed pine was mixed with the oaks and hickories. In 



