This review compares new developmental models on flowering and other vascular plants with evolutionary hypotheses formulated by Agnes Arber (1879–1960) and like-minded botanists. Special emphasis is laid on philosophical basics such as perspectivism, pluralism about evolutionary modelling, continuum way of thinking, and fuzzy logic. Arber's perspective is best labelled as F uzzy A rberian M orphology (FAM Approach). Its proponents (‘FAMmers’) treat structural categories (e.g. ‘roots’, ‘shoots’, ‘stems’, ‘leaves’, ‘stipules’) in vascular plants as concepts with fuzzy borderlines allowing intermediates (including transitional forms, developmental mosaics). The FAM Approach complements Cla ssical Plant M orphology (ClaM Approach), which is the traditional approach in botany. ClaM proponents (‘ClaMmers’) postulate that the structural categories of vascular plants are regarded as concepts with clear-cut borderlines and without intermediates. However, during the evolution of vascular plants, the root-shoot distinction and the stem-leaf distinction have become blurred several times due to developmental changes, resulting in organs with unique combinations of features. This happened, for example, in the bladderworts ( Utricularia , Lentibulariaceae). When focusing on the ‘leaf’, the FAM Approach is identical to Arber's ‘partial-shoot theory of the leaf’ and Sinha's ‘leaf shoot continuum model’. A compound leaf can repeat the developmental pathway of the whole shoot, at least to some degree. For example, compound leaves of Chisocheton (Meliaceae) with indeterminate apical growth and three-dimensional branching may be seen as developmental mosaics sharing some growth processes with whole shoots! We focus here on the FAM Approach because this perspective is especially promising for developmental geneticists studying flowering and other vascular plants. Copyright 2001 Annals of Botany Company

Received: 6 November 2000 ; Returned for revision: 9 February 2001 . Accepted: 28 May 2001


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