IOWA ACADEMY OF SCIENCES. 41 



LIVING PLANTS AS GEOLOGICAL FACTORS* 



BY B. SHCMEK. 



The importance of water as a geological agent, both 

 constructive and destructive, is so great and its effects are 

 everywhere so patent, that by contrast the importance of 

 other agents is underestimated, or in large part over- 

 looked. Among these underestimated agents plants may 

 be classed so far as their modern work is concerned. 



It is not purposed here to discuss the geological value 

 of plants as exhibited in various deposits, such as graphite, 

 coal, limestone, diatomaceous earth, etc., but rather to 

 note the w^ork which is being done by living plants. 

 Beyond the disintegration of rock by their acid rootlets 

 and rhizoids, very little destructive influence is exerted 

 by plants. They gather up much soluble material from the 

 soils, but this is returned again upon the death and decay 

 of the plants, and assists in the formation of the fine 

 surface soils. 



Each individual plant takes up but little mineral mat- 

 ter, but the amount so transferred to the surface by all the 

 plants of a given area is worthy of consideration. 



In a large part of Iowa, notably within the Wisconsin 

 drift lobe, the soils are comparatively thin, and most 

 higher plants send their roots through them into the 

 underlying drift, from which they remove some of its 

 soluble constituents. These are finally returned to the 

 surface soil, but are then more or less distinctly separated 

 from the coarser drift material with which they were 

 formerly associated. In this manner plants have no doubt 

 assisted other agencies, such as water, wind, and burrow- 



*The subject is here discussed with special reference to Iowa and adjacent territory. 

 4 I AS 



