ECOLOGICAL CROSS SECTION OF THE MISSISSIPPI. 



251 



S O U R I 



















ILLINOIS 













Bluff 



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Lowland 





River 1 Lowland 





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16 



17 



5 



18 



19 



11 



12 



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20 



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23 



26 



25 



14 



1 



11 



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1 

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rf^ 



suffic 



A laree number 



must be 



taken into consideration and under such conditions it 



frequently becomes a matter 

 knowledge in a chosen field w 



ponderat 



bed. Wh 



his 



Ecology 



theory, he was able to combine 



in one great whole, since physiographic forces, in their 

 widest sense, acting upon the surface of the globe, determine 

 not only the physical and chemical nature of the soil and 

 the topography, but by influencing the local distribution of 



character 



received 



the temperature. The term 



forces in their widest sense " is used, for it is clear that while 

 they acted 



very 



the latter has governed the extent of their influence which 

 was and is less far reaching where they act upon igneous 

 rock than where Ume or sandstones are concerned. 



Again, 



more 



others, and the position of the strata is an important factor. 



from similar initial conditions it would seem 



physiography is 



most 



consideration 



This 

 For 



determined the chemical 



of 



