The homology concept in phytomorphology – some moot points

1. Various aspects of the homology concept are critically discussed, including (a) the difference between the scholastic or ‘classical’ basis of the concept and the neomorphological (phylogenetic) or ‘dynamic’ approach, (h) the requisite of a reciprocity of the relationships among homologous elements belonging to the same conventional (i.e., a static and intranscendent) organ category, (c) the relativity of the homology concept in phylogenetic botany, and (d) the necessity of recognising categories of ab initio inhomologous objects other than those distinguished in static morphylogy (i.e., essentially, the postulation of organa sui generis — already silently practised in traditional morphological thought — along different lines). 2. Irrespective of the question whether the neological, i.e., evolutionary and hence ‘dynamic’, approach to the problem of homology is conceptually and methodologically different from the conventional, i.e., typological and ‘static’, phytomorphology, the conclusion must be drawn that the two are, in several respects, incompatible, the reasons underlying the differences in some fundamental acceptances and the ensuing interpretations being (a) the different delimitations of the intranscendent categories of morphological units (organs, etc.), (b) the invariable and ‘all or none’ equivalence of morphological entities in static phytomorphology versus the relativity of the homology relation in the ‘dynamic’ (semophyletic) morphology, and (c) the restriction of the old tenets of homotopy and homodynamy (serial homology) in the New Morphology by the additional requisite of constancy of organogenetic and histogenetic induction during the ontogenetic or morphogenetic differentiation and development of the organs and other structures involved. 3. A consequent application of the neomorphological principles leads to the rejection of several mainstays of the conventional interpretative morphology, such as the ‘sporophyll’ (foliar carpel and phyllomic stamen) concept, and also to the emendation, or the dismissal, of several allegedly phylogenetic deductions and conclusions, especially of certain aspects of the Telome Theory (in the form developed by Zimmermann). 4. The application of the homology concept to organs belonging to the same individual, and to organs differentiating during diverse phases in the life cycle of an individual (such as the alternating gametophytic and sporophytic generations, or the vegetative shoot development and the state of flowering), also involving the concepts of homotopy and homodynamy, is discussed and the limitations in the application of the concept are outlined against the background of genetic potential, phenotypic expression, determination, induction and morphogenetic differentiation. 5. The comparatively insignificant contribution of teratology to interpretative morphology is explained.