CHAPTER XX 

 PLANTS FROM AN ECONOMIC STANDPOINT 



The Value of Trees. Trees are valuable to mankind 

 in many ways. They form a protective covering for a 

 part of the earth's surface ; they prevent erosion by 



Forest Service, Washington, D. C. 

 FIG. 297. Erosion of Unwisely Cleared Slope, Western North Carolina. 



surface water; they help to retain the moisture in the 

 soil by keeping the soil loose and lessening evaporation ; 

 they furnish valuable commercial and food products 



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