318^ 



PLANT SOCIOLOGY 



Prunus, an Agrostis alba, a Brachypodium pinnatum stage, designated 

 by dominance of the species named. One and the same species may 

 take part and form stages in various (not homologous) developmental 

 series. Thus, B. pinnatum is constructive in the growing Xerobrome- 

 tum of the limestone hills of the upper Rhine (Issler), while Tansley 

 (1925) considers it destructive for the Bromus eredus-Festuca ovina 



Fig. 160. — Cyperus capitatus, initial stage stabilizing a dune near Agadir. {Photo by 



Maire.) 



association of southern England, and Scherrer (1922) and Koch (1926) 

 point out its decidedly destructive activity in the Molinietum of 

 northern Switzerland. The arctic-alpine creeping shrub Dryas 

 odopetala is of great constructive importance not only in the north but 

 also in countless alpine turf communities in the Carpathian, Pyrenees, 

 and Rocky Mountains. In Alaska it is replaced by the related D. 

 drummondn, a pioneer of the porous morainal soils in the neighborhood 



