70 A TEXT-BOOK OF GRASSES 



has been reclaimed. In the United States there are several 

 areas of sand-dunes, the most important being on Cape 

 Cod near Provincetown, Cape Henry, Virginia, along the 

 south end and east side of Lake Michigan, and along the 

 Columbia River, Oregon, in the semi-arid region. Sand- 

 dunes are formed by the wind blowing the dry sand. 

 Dunes that are bare of vegetation shift gradually as the 

 prevailing wind blows the sand over the crest. When 

 vegetation becomes established the wind is unable to 

 move the sand and the dunes become fixed. 



Moving dunes may do much damage when formed in 

 the vicinity of the works of man by covering up buildings 

 or railroad tracks, or, when formed near streams or 

 harbors, by diverting the course of the one or filling the 

 other, or when formed near a forest which they may over- 

 whelm. Sand-dunes are formed along the sandy shores 

 of the ocean or of large lakes when the prevailing winds 

 are from the water. The waves are constantly throwing 

 up sand w^hich, when dry, is blown upon the beach, form- 

 ing hills. The same often occurs along rivers in dry regions, 

 as along the Columbia above the Dallas, and along the 

 Arkansas in western Kansas. 



92. Reclaiming sand-dunes. — Moving dunes are 

 worthless for agricultural purposes and may be a menace 

 to property. The first step in reclaiming such dunes is 

 to fix the sand by applying a covering to prevent its being 

 shifted by the wind. Interior dunes have been success- 

 fully fixed in Europe by covering wdth cut heather, a 

 common plant in sandy wastes. In other places brush or 

 rows of sticks thrust into the sand have served the pur- 

 pose. One of the most successful methods has been the 

 planting of beach-grass. After the shifting of the sand 

 has been prevented l\y any of these methods, trees are 



