1 14 ROBERT SMITH [February 



-etum, e.g. Callunctum, Pinetum, etc. Celakovsky (1869) called by the 

 same term, " formation," groups of species of similar habit, station, and 

 distribution, which could be regarded as having migrated together into 

 the country ; he thus gave the word " formation " a meaning in floristic 

 plant geography. Drude (1889) attempted to compromise by dis- 

 tinguishing the smaller " formations " as " Bestande," and Weber 

 (1892) similarly classified them as primary and secondary 

 " formations." The original definition of the term by Grisebach as a 

 division of the landscape had lost its force from the newer biological 

 way of regarding the "formation." It was now no longer strictly 

 comparable to a geological formation, and could only in an indirect 

 way be regarded as something " formed." 



From the nature of the object sharp definition is impossible. 

 Warming (1896) has recommended the disuse of the term; in its 

 wide sense he says that its meaning can be quite well expressed by 

 the word " Vegetation," and for groups of plants associated together 

 by common habits he employs the term " Pflanzenverein " (in Danish 

 " Plantesamfund "). In English we have named these unions or 

 communities " Plant Associations," as expressing the nature of the 

 relationship of the plants to each other. This expression is employed 

 in a similar sense in papers by Flahault (1897 a), Schroeter (1894), 

 Schneider (1897), etc. 1 



An association may be as narrow as that between two symbions, 

 or as wide as the entire vegetation of the globe. In the description 

 of the vegetation of any region it depends entirely upon how detailed 

 a survey is intended, how many associations it may be subdivided into ; 

 if only a general survey, then only the chief and conspicuous associa- 

 tions in the landscape may be treated of, if a complete survey, then all 

 down to the very smallest subdivisions await research. The complete 

 knowledge of the " Vegetation " of any country demands such a 

 complete survey. The methods organised for the study of " formations " 

 apply equally well to " associations," since the " formations " selected 

 are always particular instances of association. 



These methods for the description of the " Vegetation " of a country 

 can now be summarised. We require to know : — 



(a) The chief associations into which it may be divided. 



(b) The particular conditions of heat, light, moisture, and food 



distinguishing each association. 



(c) The particular adaptations or life-forms of the species of each 



association. 



(d) The relations between the species — 



(1) Dominant social forms. 



] One must point out, however, that the word " Pflanzenassociation " has sometimes been 

 used by Loew (1879), Hock (1895), and some other authors with a special meaning in 

 floristic plant geography, similar to the application of the term " formation " by Celakovsky 

 as mentioned above. 



