(■) 



soil is still a pure santl. but since it is jn-otected by the trees 

 from the wind and from the lijiht and heat of the sun. it does 

 not dry out so rapidly. For the .same reasons the atmospheric 

 humidity is con.served. and the oxidization of orji'anic matter 



Other species: C/irysopsix cninportim. Ruilhcrkia hirta, Boutelona 

 hirsuta, Euphorhla Oeifcri. The trees were nor included. 



lyin>i on or near the surface of the sand is retarded. The an- 

 nual leaf-fall is of course much larger, and instead of being 

 blown about by the wind it is held by the den.se growths of 

 /i'//«.N- and rrr/rm. and forms a layer over the sand which in- 

 creases annually in thickness. This holds a portion of the 

 rain-water at the surface of the sand, and is eventually con- 



See p. 1.59. 



