128 STRUCTURE AND UNITS OF VEGETATION. 



(1913), and Rubel (1915) have proposed a physiognomic system based upon 

 Latin. The physiognomic basis seems much less satisfactory, and the use of 

 Latin compounds certainly leaves much to be desired in the matter of uni- 

 formity, brevity, and euphony. While Clements and Diels use the trans- 

 Hterated form of the suffix, as in hylium, helium, etc., Moss objects to this 

 because of the fear that it would lead to confusion with neuter generic and 

 specific names. Such confusion would be impossible it the formationaJ terms 

 are not capitalized, as was originally intended. Since uniformity is more 

 desirable than any other feature of terminology, the modification of the term 

 by Moss is accepted here, as it has become more or less current in British 

 pubUcations. Since climax formations are clearly dependent upon the flora, 

 it seems impossible to ignore this fact in the name. Moss objects to the use 

 of the names of dominant genera, as in "Eriophorum-Scirpus oxodion," 

 because it is not really definitive, as no indication is given of the species of 

 Eriophorum or Sdrpus. Further objection is raised because the oxodion com- 

 prises not merely the two associations designated, but probably at least two 

 dozen. These objections disappear in the developmental treatment of forma- 

 tions, since there are rarely more than two associations in a formation. If 

 Bvlbilis-Bouteloua-poiori is thought too long for the name of the short-grass 

 climax of the Great Plains, it can be called simply Bouteloua-poion, just as a 

 similar climax elsewhere might be the Stipa-poion. The greater definiteness 

 both as to floristic and region seems to render such formational names prefer- 

 able to Moss's a-oxodion, ^-oxodion, etc. 



CLIMAX UNITS. 



Associatioii. — ^The association has had as varied a history as the formation. 

 Not only has the one been used for the other, but even when they have been 

 employed in the proper relation the units to which they have been applied 

 have varied greatly. As has been already indicated, the association as usually 

 understood becomes what is here termed the consociation, in so far as it is a 

 climax community. This is the association with a single dominant. While 

 many associations of two or more dominants have been recognized, these are 

 practically all what Moss (1910 : 38) terms subordinate associations, that is, 

 successional communities or associes (plate 35, a, b). 



The association as here conceived bears the accepted relation to the forma- 

 tion. The term is restricted, however, to those climax communities which are 

 associated regionally to constitute the formation. The associations agree 

 with their formation in physiognomy and development, but differ in floristic 

 and to a certain though unknown degree in habitat. Hence they are recog- 

 nized chiefly by floristic differences. Associations are marked primarily 

 by differences of species, less often by differences of genera. At the same 

 time, their organic relation to each other in the climax unit or formation 

 rests upon floristic identity to the extent of one or more dominants, as well as 

 upon the fundamental development and the life-forms. For example, the 

 Bouteloua-poion contains two associations,' the Bulbilis-Bouteloua-association, 

 and the Aristida-Bouteloua-association. While the species of Bovteloua and 

 Aristida are mostly different in the two, one or more species of both genera 



'See note, p. 180. 



