46 



NATURE STUDY REVIEW 



-Feb., 19 J 3 



Figure 4. — Roots growing from the trunks of cottonwood trees and 

 exposed by migration of the dune. (Fuller.) 



and steep leeward slopes. Since the lee slope is protected from 

 the wind it will be just as steep as loose sand can stand. This 

 shape is represented in miniature by the wind ripples frequently 

 seen on a sandy surface (Fig. 3). 



If a dune acquires a protective covering of vegetation it 

 will stop traveling and become stable. But when for any reason 

 plant life ceases to protect it, or man carelessly cuts into it, the 

 wind soon attacks the exposed part and dune-destruction and 



