150 



MISSOURI BOTANICAL GARDEN. 



of from one-half to one foot. Where 



been 



for cultivation, the humus contents soon leach out, forming 

 the unproductive 'Svhite lands." As llilgard* points out, 

 the light color means the scarcity or absence of both humus 



and ferric hydrate. 



At the base of the cliffs is a notable deposit of soil covering, 

 in marty places entirely, the talus, this especially where the 

 loess overlies the limestone. Here the soil is continually 

 being added to by the action of the rills and rivulets which 



and 



but 



unde 



talus. Such lower hillsides ordinarily possess 



a luxuriant vegetation. 



The bottoms on the Missouri 



from the deposition, by the Mississinp 



hea\^ loam mixed with sand 



nf eolluvial soil broudit dov 



• . • 



n from the uplands. This soil 

 is rich in lime and in the course of time has been covered by 

 a black humus. 



same 



immediately 



on the St. Clair county side and which frequently occur 



bank 



and 

 d CO 



recognized. In some places on these islands there are large 



accumulations of clay. 



Back of the stretches of sand lies an area the soil of which 



is composed of heavy loam. 



mixture 



deposits covered by the matter 



d down from ' 



Its soil is 



highly calcareous, sharply contrasting with that of^ the 

 sandy stretches. It is the Yazoo loamf typical of the Missis- 

 sippi bottoms and highly productive. 



The soil at the bottom of the bluffs is partly residual, re- 



* Hilgard, E. Soils. 285. New York. 1907. 



t Fippin, E. 0., and J. A. Drake. Soil Survey of the O'Fallon Area, 

 Missouri-Illinois. Kept. U. S. D. A., Bureau of Soils. G : 815. 1904. 



/ 



