444 PRACTICAL BOTANY 



are many kinds of soil-holding plants which, if properly placed, 

 will prevent erosion in its earliest stages, and these should be 

 used. In open, 'hilly fields which are exposed to erosion, grass 

 and meadow crops are desirable, since their roots help to hold 

 the soil throughout the whole year. In such cases the roots 

 and stems help to prevent the rapid run-off of the surface 

 water. The very things that need to be done in the cultiva- 

 tion of plants increase the danger of loss of soil where rapid 

 flow of the surface water cannot be prevented. In hilly fields 



FIG. 345. A Mississippi hillside farm, newly cleared 



It is plowed and planted in rows around the hill to retard erosion. In such regions 

 the soil when plowed washes away rapidly. Photograph furnished by W. N. Logan 



it is often difficult, sometimes impossible, to prevent erosion. 

 In some localities the rows of growing plants are arranged 

 across the slope of the hill (Fig. 345), thus assisting some- 

 what in retarding the surface flow of water. If cultivation is 

 continued in such places, the soil soon erodes, and it is with 

 extreme difficulty that any plants gain a foothold (Fig. 346). 

 In some foreign countries hillsides have been saved for cultiva- 

 tion by a process of terracing. The terraces are constructed in 

 such a way that the soil upon each is level or slopes toward 

 the hill, thus retarding or preventing erosion (Fig. 347). 



