372 PLANT SOCIOLOGY 



id') Ground layer mostly closed (very rarely absents 

 dominating the layer above, e.g., Spagnetalia, high 

 moor, 

 (ii) Several-layered communities; lower layers more or less 



influenced by upper. 



(a') Mostly three layered, often edaphic or biotic. Depend- 

 ent epiphyte communities lacking or feebly developed. 

 Shrub communities. 



(6') Mostly more than three layered, often as climax in 

 permanent equilibrium with the environment. Depend- 

 ent epiphyte communities mostly present, e.g., forest 

 communities. 



5. Classification of the Communities of Higher Plants of Bas 

 Languedoc, France. — The following table of the plant communities of 

 Bas Languedoc is offered as an example of the practical application of 

 the principles of classification elaborated above. The vegetation covers 

 a rather large area which has been intensively studied, and the table 

 comes as the culmination of more than fifteen years of investigation. 

 As a result of these studies, records exist of the analysis of many 

 typical stands (30 from certain associations) taken from different parts 

 of the area. The segregation of the associations into alliances, orders, 

 and classes is made on the principle of floristic affinities. 



Every unit, however, whether association, alliance, order, or class, 

 has its special ecology and represents a more or less definitely circum- 

 scribed ecologic unit. 



The arrangement of the higher units follows a sociological progres- 

 sion. It is, moreover, interesting to note that in the area under 

 consideration this arrangement brings out at the same time a synge- 

 netical scale which corresponds to the progressive succession. The 

 higher parts of the scale approach more and more closely to the climax. 



Attention may also be called to the fact that the groups at the 

 base of the classification have, in general, a wide geographic distribu- 

 tion; in the upper groups territorial localization is more and more 

 pronounced, so that the six final classes of shrubs and trees are almost 

 exclusively limited to the Mediterranean region. These final classes 

 are preeminently those which reveal the phytosociologic individuality 

 of this region and which characterize it so wonderfully as possessing a 

 highly specialized type of vegetation. 



