25 
Fundamental Units of Vegetation. 
dependent species. For example, it is difficult to believe that 
British beechwoods on the Chalk belong to the same association as 
those on the Greensand. 
W. G. Smith (1904 : 620) held that the “ nomenclature of 
ecological plant geography, in spite of attempts to systematize, is at 
present too chaotic to attempt an exact definition of the terms 
used. For the present, it is safer to designate associations 
by prefixing the names of the dominant plants. The smaller 
associations may be designated by plant names, e.g., Juncetum, 
Caricetum, Psammetum, etc., or by prefixing generic and (in some 
cases) specific names, e.g., Molinia association, f uncus squarrosus 
association, etc.” 
Pethybridge and Praeger (1905) based their work on the 
recognition of associations, which they arranged into “zones.” In 
the moorland “zone,” they described, among others, associations of 
Calluna vulgaris , of Vaccinium Myrtillus, of Scirpus ccespitosus, and 
of Eriophortim angustifolium. 
Olsson-Seffer (1905) stated that a formation may be sub¬ 
classified into associations and these again into “communities,” 
the latter being indicated by the termination -etum. 
Clements (1905: 295-6), on very unconvincing grounds, used a 
new term “ consociation, or better consocies,” for the concept of the 
plant association. There is, however, no doubt as to his meaning ; 
for he stated that his “consocies, under the term association. 
have been recognized for several years.” There appears no likeli¬ 
hood that Clements’ new term will come into general use ; but it 
must be stated that Clements’ concepts of the formation and its 
primary subdivisions were perfectly well-defined, and in thorough 
accord with modern usage. 
Hardy (1905: 45) accepted the definition of the association 
given by Pavillard (1905), who was quoted to the following effect:— 
“ Une association vegetale est un groupement spontane, un peuple- 
ment naturel ou les unites specifiques, generalement etrangeres les 
unes aux autres, vivent cote a cote, avec le profit exclusif de chacune 
pour objet, mais ou des formes biologiques tres differentes peuvent 
etre juxtaposees et meme subordonnees entre elles, suivant la 
diversite des exigences satisfaites par les conditions du milieu modifie 
ou non par les organisimes conccurants.” This definition, from the 
standpoint of the modern subdivision of the formation into associa¬ 
tions, is rather vague. 
Brockmann-Jerosch (1907 : 248-9, etc.) divided his formations 
