various conditions such as parasitism and saprophytism. cf. 

 Obligate parasite. 



Fairy Ring 



A circle of mushrooms arising from underground mycelial 

 growth, usually accompanied by a luxuriant ring of vegeta- 

 tion, fairly common in grasslands. 



Fall Line 



A line connecting the points where rivers leave the 

 uplands for the lowlands, marked by an increased slope and 

 waterfalls, e.g., the Atlantic coastal plain adjoining the Ap- 

 palachian Mountains. 



Fallout 



The dropping to the earth from the air of solid material, 

 particularly the radioactive dust from atomic explosions. 



Fall Overturn 



See Spring overturn. 



Fallow 



Refers to cropland left idle except for tillage in order to 

 destroy weeds and accumulate water and nutrients for use 

 of a crop to be planted later, cf. Summer fallow. 



False Annual Ring 



More than one of the Growth rings that may be produced 

 in woody plants in a single season. 



Family 



In the classification of organisms a group of one or more 

 related genera, e.g., the rose family in which the roses, straw- 

 berries, etc., are classified. In ecology it has been used for a 

 community comprising individuals of a single species. 



Fasciation 



The condition in plants in which stems and branches 

 have grown together to form a malformed and flattened 

 structure. 



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