Structural and dynamic descriptions of the development of Utricularia foliosa and U. australis

Abstract

In this developmental investigation of Utricularia foliosa and U. australis by means of scanning electron microscopy we demonstrate the relativity of morphological facts and descriptions. We provide several descriptions in terms of the structural categories "stem" and '"leaf." These contrasting, if not contradictory, descriptions are complementary to each other, i.e., they present different aspects of the unusual complexity of these species. In addition to these structural descriptions, we provide a dynamic description in terms of process morphology. According to this dynamic approach, each form is seen as a process combination. Structural change during ontogeny and phylogeny is a change in process combinations. From this point of view, the unusual process combinations of the two Utricularia species do not pose a morphological problem, although they cannot be clearly assigned to mutually exclusive categories such as stem and leaf. In addition to the clarification of the developmental morphology of the two Utricularia species, this investigation illustrates process morphology as a general approach to the description and comparison of plant form. The relevance of this approach to other biological disciplines such as cladistics is briefly indicated. Key words: Utricularia, Lentibulariaceae, shoot development, leaf development, morphogenesis, process morphology.