THE UNITS OF VEGETATION. 119 



from one formation to another, and the succession of associations within one 

 and the same formation; and Moss enimciated a statement of the formation 

 from the latter point of view." 



As indicated above, Moss's intention was to base formations primarily upon 

 habitat. Since he regarded the latter chiefly in the Ught of soil relations, it 

 was inevitable that he should group together in the same formation the serai 

 associations, such as forest, scrub, and grassland, which are due to efficient 

 differences of light and water-content. As a consequence, Moss's concept of 

 the formation was only incidentally developmental, and his actual formation 

 is a different thing from the cUmax formation. While the latter is the out- 

 come of development, it consists of two or more related climax associations, 

 and not of a climax association plus two or three antecedent developmental 

 associations. The views of Moss in regard to the formation were adopted by 

 Moss, Rankin, and Tansley (1910) and by Tansley (1911). 



Schroter's concept. — Schroter (1902 : 68) has traced the outlines of a topo- 

 graphic-physiognomic system of formation groups. The unit of this system 

 is the local association, which characterizes a definite locality of uniform 

 habitat. The diagnosis of the formation unit comprises (1) locahty, (2) habi- 

 tat, and (3) plant-cover, (a) physiognomy, (6) life-forms, (c) list of species. 

 A formation comprises all the association types of the entire earth, which 

 agree in their physiognomy and ecological character, while the floristic is 

 immaterial. The series of units is as follows: 



I. Type Vegetation type Grassland. 



fFormation group Meadow. 



II. Formation. . . < Formation Dry meadow. 



[ Subformation Alpine dry meadow. 



I Association type Nardetum. 



Subtype Nardetum with Trifolium. 



Facies Nardetum (Nardus dominant). 



Local association . Nardetum at Gotthard. 



In contrast to Schroter's topographic-physiognomic concept, Brockmann- 

 Jerosch (1907 : 237) considers the first task in the study of plant communities 

 to be their limitation and description upon a physiognomic-floristic basis. 

 The author expressly refrains from defining his concept of formation and asso- 

 ciation, but the essence of it is readily gained from the argument. In spite 

 of the difference of emphasis upon habitat and floristic, the viewpoints of 

 Schroter and Brockmann are very similar. They both accept the "pigeon- 

 hole" concept of the formation proposed by Warming and justly criticized 

 by Moss. 



Gradmann's concept. — Gradmann (1909 : 97) has also emphasized the impor- 

 tance of floristic at the expense of other criteria: 



"Since the physiognomic and ecological viewpoints have been shown inade- 

 quate for a botanical distinction, there remains the sole possibility of ground- 

 ing formations upon their floristic composition. In fact, the floristic method is 

 the only one which can be completely carried out in a monographic treatment 

 of formations. Many a well-marked and natural formation can be dis- 

 tinguished in no other way than by its floristic composition. On the other 

 hand, every formation determined by physiognomic characters can be circum- 

 scribed just as well floristically. At the most one thereby obtains somewhat 



