CHAP. XXXV ASSOCIATIONS 145 



An association is a community of definite floristic composition within 

 a formation ; it is, so to speak, a floristic species of a formation which 

 is an oecological genus. 



Wliile the formations in different floras may be the same, associations 

 are dependent upon the character of the flora of the country concerned. 



Terminology. Associations may conveniently be denoted according to the plan 

 suggested by Schouw,' by the addition of the suffix -etum to the name of the 

 characteristic species or genus ; for instance, in the reed-formation there are 

 phragmiteta, scirpeta, typheta, and the like ; similarly there are saliceta, pineta, 

 and so on ; in order to indicate the species concerned the specific name has to 

 be added, thus, for example, scirpetum Scirpi lacustris, saUcetum Salicis albae, 

 pinetum Pini sylvestris, pinetum Pini montanae ; or more briefly, scirpetum lacustris, 

 salicetum albae, and the like.' This terminology corresponds somewhat to popular 

 usage, in which two words are combined and one of them indicates the species, as 

 is the case with the terms beech-forest, oak-forest, birch-forest, or Kerner's terms, 

 gold-beard ' meadow, feather-grass * meadow. 



When an association is composed, not of a single prominent species, but of 

 several in equal shares, it may be denoted by a compound term, for instance, scirpo- 

 phragmitetum, fago-quercetum, or in some other way for instance, by its popular 

 name.* 



In many cases associations are brought into existence within the 

 formation by minor distinctions in the soil, because different species 

 react in a shghtly different manner. In other cases accident seems 

 to decide the question : the species which first colonized the spot will 

 subsequently be able to maintain itself against others, as in the instance 

 of the reed-associations clothing the banks of rivers and lakes in north- 

 temperate Europe. 



Associations may occur irregularly as patches in the formation ; or 

 may exhibit a zonal arrangement. The latter is always the case when 

 the formation grows in water (in which case depth decides the matter), 

 or on the banks of rivers, lakes and pools, where subterranean water can 

 play its part ; with increasing height of soil above the water-table vegetation 

 y I displays a zonal change.^ Plants react to infinitely small differences 

 in the water-content of soil. In very many cases these belts of plants 

 at the same time represent developmental series, inasmuch as each 

 association is successively expelled by the next one. 



Associations may also be dependent upon shade and other oecological 

 factors. An alpine meadow has a different floristic composition accord- 

 ing as it clothes the northern or southern slope of a mountain, yet it 

 remains a typical meadow, and thus unchanged as a formation ; grassy 

 surfaces fining a railway differ floristically according to the aspect,' 

 )ut they are merely different species, or, in other words, different associa- 

 tions, of the same formation. 



D VARIETIES OF ASSOCIATION 



As in oecology a formation may be regarded as a genus, and an 

 issociation as a species, so we may also recognize oecological varieties 



' Schouw, 1822, who referred to ericeta, rhododendreta, arundineta, pineta, 

 'ageta, and the like. ' See Cajander, 1903. 



' [Chrysopogon Gryllus]. * [Stipa]. ' See C. Schroter und Kirchner, 1902. 

 See Raunkiar, 1889; Warming, 1890, 1906; MacMillan, 1896; Magnin. 



[893, 1894; Pieters, 1894; Clements, 1905; Shantz, 1905. 

 ^ Stebler und Volkart, 1904 ; Stcnstrom, 1905. 



WARMING 



