582 A TEXTBOOK OF BOTANY [Ch. XIV 



the totality of associates which tend to go with a given domi- 

 nant form, are called associations, or sometimes societies, 

 though this latter word has often been used for formations 

 and associations without distinction. Thus an association 

 is the particular assemblage of vegetation forms which ac- 

 company a given dominant or combination of dominants. 

 Defined in another way, an association is the aggregation of 

 forms which live together on the same area of ground. In 

 case a formation has but one dominant vegetation form, it 

 has ordinarily only a single association, but where two or 

 more dominant forms occur, there will be different associa- 

 tions. Other groups, subordinate to the associations, have 

 been recognized by investigators, just as varieties are recog- 

 nized among species, but the matter is recondite and little 

 understood. In these minor groups, those features of species 

 which are not connected with their vegetation forms come also 

 into play, complicating the combinations. 



In the description of associations, it is easy and convenient 

 to designate the species which are represented in the vegeta- 

 tion forms, and in this way the connection is made between 

 the vegetation and the flora. Indeed, associations are often 

 named scientifically by using the stem of the name of the 

 dominant form with the termination -etum, e.g. Pinetum, 

 Quercetum, etc., which terms should now be self-explanatory 

 to the student. No scientific system for naming the forma- 

 tions has yet come into use. 



The relations of these groups may be summarized by say- 

 ing that the species of a country tend to collect in the habitats 

 which their vegetation forms happen most nearly to fit; 

 the vegetation forms tend to collect into associations accord- 

 ing to the most natural manner of interlocking around the 

 dominant forms of a habitat ; the associations tend to collect, 

 according to the similar habits of thef.r dominants, into 

 formations; the formations are linked in areas and zones 

 with the habitats ; and collectively the formations make up 

 the vegetation of a country. 



