60 Transactions of the Academy of Science of St. Louis 
The results of the analysis indicate that definite relation- 
ships exist between bed rock and the percentage composition of 
the associated forest?4, but most of these relationships appear to 
be indirect. Many species of trees occur throughout the area, 
the woods on dissimilar rock types differing chiefly in the relative 
abundance of the various species. The greatest differences in 
the forest composition exist between woods growing in unlike 
topographic situations rather than between woods similarly situ- 
ated but on different rocks. This strongly suggests that bed and 
mantle rock, while exerting some direct influence on the nature 
of the forest, especially on indicators, function as controls prin- 
cipally through the media of slope, drainage, and exposure to 
sunlight. 
Within the Ozarks there are some broad, gradual vegeta- 
tional transitions which bear no apparent relation to the bed and 
mantle rock. The diversity of the forest decreases from south- 
east to northwest, due to increasing climatic severity and to 
greater distance from the Gulf Coastal Plain, the source of many 
of the forest elements. In general, the Ozarks are forested with 
a dense growth of small trees averaging thirty feet in height, but 
including some larger trees remaining from a former open, grassy 
woodland. The small size of the timber is due primarily to the 
extremely slow growth of the most abundant species, the post 
oak, and to selective cutting of the larger and more desirable trees. 
The Mixed Forest Regions, the example chosen, includes 
several distinct vegetational assemblages, each of which is as- 
sociated with a definite bed rock type. On the Burlington-Boone 
caps Of the higher hills the forest is dominated by red, white. 
and black oaks which collectively constitute over 50 per cent of 
the timber. Southern pine is the indicator and locally is the 
most abundant species. The oak assemblage indicates soil fertil- 
24. Compare Figures 5 and 10. 
25. Figure 10. 
