VIcoriation 



The phenomenon of ecologically equivalent species, or 

 taxonomically corresponding species, replacing (or "substi- 

 tuting") each other in similar environments in different 

 geographic areas, e.g., caribou in North America and rein- 

 deer in Eurasia. 



Vicinism 



The condition of variation in a population or in an 

 individual resulting from growing in close proximity to 

 other organisms. 



Virgin (Forest, Community, Region, etc.) 



Refers to objects or aggregations, especially vegetation, 

 essentially uninfluenced by human activity. 



Virology 



The branch of biology dealing with viruses. 



Virus 



A submicroscopic parasite in organisms consisting of 

 nucleic acid and protein, incapable of increasing in number 

 outside of the host cell, causing various diseases in plants 

 and animals. 



Vitalism 



The doctrine that life processes are caused by some force 

 that cannot be measured, in addition to the operation of the 

 laws of chemistry and physics. 



Vitality 



The condition of vigor of organisms; the capacity to live 

 and complete the life cycle. Braun-Blanquet classified plants 

 according to states of vitality into four categories. 



Vitamins 



Organic substances required in minute quantities by 

 plants and animals in their metabolic processes, cf . Thiamine. 



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