Beginning with some fundamental considerations on the study of vegetation Kuoch describes and estimates accordingly the methods of several schools of plant sociology, both from the theoretical and the practical points of view, namely +) the belt/model system of E. Schmid, Zürich, +) the predominance-constancy system of Du Rietz, Upsala, +) the floristical-statistical system of Zürich-Montpellier, +) the series of development system of E. Aichinger, Vienna. Two of the conclusions may be pointed out: !. In the study of vegetation the examination of the structure of the associatiom comes first, followed ba the discussion of origin, development, history, extension, possibility of conservation and standing -place of the association. But the definition of the units has only to be made up of those characters. which permit to recognize the association on the spot, namely of the inventory of species and the characters of structure and growth of the association. 2. Amongst the different principles of workiing and systems of grouping applied by the schools of plant sociology, those of Zürich-Montpellier are considered to be espacially successfull. Moreover, this method and system are almost generally adopted by people dealing with forest plant sociology and study of site.
