IN DETAIL 299 



nite phenomena of alternation which can be found anywhere. The family 

 and the community, though the latter is less distinct in outline, are equally 

 valid structures, the proof of which anyone can obtain by thorough methods 

 of study. 



348. Nomenclature of the divisions. The suffix -ettim is used to desig- 

 nate a consocies of a formation, e. g., Picetum, Caricetiwi, etc. When two or 

 more species characterize the area, the most important, or more rarely, the 

 two are used. The termination used to designate a society is -He, as Asterile, 

 Sedile, Rosile. The suffix which denotes the community is -are, and for the 

 family, it is -on, viz., Giliare, Bromare, Bidenton, Helianthon, etc. Layers 

 are indicated by the affix -anitnt, as Opulasteranum, V erhesina-Rudhecki- 

 amim, etc. It is evident that these suffixes, like the terms to which they re- 

 fer, must be used always for the proper divisions if they are to have any 

 value at all. There has been a marked tendency, for example, to use -etum 

 in connection with the names of groups of very different rank. It is hardly 

 necessary to point out that such a practice does not promote clearness. The 

 following tabular statement will illustrate the application of both terms and 

 suffixes : 



Picea-Pseudotsuga-hylinm formation (-ium ) Paronychia-Silene-chalicium 



Picetum consocies (-etum) Paronychietum 



Opulaster-Ribesanum layer ( -anum) 



Opulasterile society (-t7^) Androsacile 



Thalictrare community (-ar^) Festucare 



Pirolon family (-on) Arenarion 



349. The investigation of a particular formation. A comprehensive and 

 thorough study of a formation should be based upon as many examples of it 

 as are accessible. The example which is at once the most typical and the 

 most accessible is made the base area. This plan saves time and energy, re- 

 duces the number of instruments that are absolutely necessary, and estab- 

 lishes a common basis for comparison. The inquiry should be made along 

 four lines, all fundamental to a proper knowledge of the formation. These 

 lines are: (i) the determination of the factors of the habitat, (2) a quadrat 

 and a transect study of the structure of the formation, (3) a similar inves- 

 tigation of development, (4) a floristic study of the contiguous formation^ 

 with special reference to migration. The sequence indicated has proven to 

 be the most satisfactory, and is to be regarded as all but absolutely essential. 

 Naturally, this applies only to the order in which the various lines are to be 

 taken up, as they are carried on together when the work is fully under way. 

 Since instrument and quadrat methods have already been given in detail, it 



