Systematic, phylogenetic, and ecological wood anatomy — History and perspectives

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Following an account of the early beginnings of wood anatomy in the seventeenth century, with special emphasis on the often neglected role of Antoni van Leeuwenhoek, history and achievements of systematic, phylogenetic, and ecological wood anatomy are reviewed. Most current concepts in systematic wood anatomy had been formulated towards the end of the nineteenth century. A discussion is given of the major trends in xylem evolution (the ‘Baileyan trends’), and of possibilities of reversions of these trends, especially in vessel element (or cambial initial) length. Recently surveyed data on the fossil pollen record of angiosperm families (by Muller) are compared with the occurrence of primitive or advanced wood anatomical characters in extant representatives of these families. Families of Cretaceous origin (as deduced from fossil pollen records) show a much higher incidence of primitive vessel, fibre and parenchyma features, but in families of Tertiary origin the same degree of specialisation occurs as in the extant world flora. For ray type and storied structure no such trend exists. In a discussion of the achievements of ecological wood anatomy, some general trends on vessel element and fibre dimensions, and vessel perforation type as related to temperature and drought are reviewed. Tentative trends for ray histology, parenchyma abundance and fibre type are explored. Rigid adaptionist interpretations are criticised: in addition to adaptive ecological trends, functionless trends imposed by correlative restraints and ‘patio ludens’ variation (sensu Van Steenis) are advocated. Priorities for future research, in order to promote further integration of the various aspects of comparative wood anatomy, are listed. These are of equal significance in pure and applied research.