Duckfoot 



An implement with horizontally spreading V-shaped 

 blades which provide shallow cultivation without turning 

 over the surface soil or entirely burying crop residues. 



Ductless Glands 



See Endocrine gland. 



Duff 



A general term for vegetal material in forests, including 

 the fresh litter and well decomposed organic material and 

 humus. See A horizon. 



Dune 



A mound or ridge of sand piled up by the winds, com- 

 monly found where sand is abundant as along lake shores, 

 sea shores, and in desert and semi-desert areas. 



Dune Sand 



(1) An area of sand accumulated by wind action into 

 dunes or hummocks, usually free from vegetation or sparsely 

 vegetated and undergoing erosion and redeposition by the 

 wind. (2) Refers to sand that has texture size of 0.1 to 0.4 

 mm. in diameter which has been piled up by the wind. 



Duriherbosa 



Vegetation consisting of herbaceous plants whose above- 

 ground parts die during winter, e. g., grasslands. 



Durilignosa 



Vegetation consisting of broad, hard-leaved Sclerophyll 

 trees or shrubs, e. g. chaparral, (q. v.). 



Dust Mulch 



A shallow layer of loose surface soil. 



Dust Whirl (Dust Devil) 



A small, intense, vortical disturbance, usually only a few 

 yards in diameter, in which large volumes of dust and debris 



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