as dry deserts, salt deserts, cold deserts, strand vegetation, 

 dune communities, and rock communities. 



Desert Grassland 



The extensive grassland in southwestern United States 

 and Mexico, characterized in part by several species of grama- 

 grass, three-awn grass, and curly mesquite. 



Desert Pavement 



The stony or pebbly surface of land after the fine ma- 

 terials have been removed by wind or water action. 



Desiccation 



See Siccation. 



Desilting Area 



An area occupied by vegetation such as grasses or shrubs 

 used solely for the deposition of silt and other debris from 

 flowing water, located above a reservoir, pond, or field which 



needs protection from accumulation of sediment. 



i 



Desilting Basin 



See Settling basin. 



Detention Dam 



A dam built for the purpose of storing streamflow or 

 surface runoff, and to control the release of such stored water. 



Deuterogenesis 



The development of adaptive characteristics in late stages 

 of the life-cycle, e. g., wings of insects, cf. Caenogenesis. 



Devonian 



A geological period in the Paleozoic era, which began 

 about 325 million years ago and lasted about 45 million 

 years. 



Dew-point 



The temperature at which a certain body of air is capable 

 of holding no additional water vapor, so that any decrease 



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