Plant -assoGiatians and their Characters 11 



The highest type of association within a formation 

 (often woodland), to which development 

 SbordS^ tends, is called the chief association of the 



associations. formation. In the absence of disturbing 

 factors, such as the interference of man, 

 landslips, and so on, the chief association will ultimately 

 occupy the natural formation-area to the exclusion of the 

 other associations, which may be collectively designated 

 subordinate associations^. But other associations may attain 

 to a considerable degree of stabiHty as the result of an 

 interference with the normal course of development, even 

 apart from continuous human interference. 



In some cases smaller differences of habitat, of scarcely 



sufficient importance to warrant the recog- 



. nition of distinct associations, may never- 



and facies. theless bring about certain changes in the 



vegetation. Conununities thus differentiated 



may be called sub-associations. In other cases where 



there is no definite segregation of distinct communities, 



but the vegetation varies in character, we may speak of 



different facies of the association. 



A plant-association, especially a chief or other stable 

 association, is generally dominated by a single social 

 species (e.g. in many woodland associations), or by several 

 social species of the same or similar plant form, as in 

 grassland. These dominant species determine the physio- 

 gnomy of the association and largely also (by their habit 

 and mode of growth, by the protection they afford, the 

 shade they cast, and so on) the associated species found 

 among or beneath them'. 



1 Moss, " The Fundamental Units of Vegetation," Xtw Pkyt. Vol. ix. 

 p. 38. 



- The technical name of an association is formed by the addition of 

 the sufiix -etum to the stem of the generic name of the dominant species, 

 followed by the specific name in the genitive. Thus a wood dominated 

 by the pedunculate oak is a Quercetum BoMiris, a name which is really an 



