Form and Function in Angiosperm Pollen

n pollen morphology, as for other characters, the relation between origin, form, and function is basic for taxonomic interpretation.Physicochemical limitations to form development, structures into ep s transfer of function is знане ed, and two new evolutionary trends аге recognized.Peristasy involves reduction of colpate ectoapertures with retention of endoapertures, sphericity, and an exine structure distributing harmomegathic stresses equally over the pittance: Latistasy results in a latitudinally oriented harmomegathic stress pattern and has been achieved in different ways.The independent origin of such trends in unrelated taxa is stressed.In evaluating the significance of pollen characters, be it for taxonomic purposes or for interpretation of the fossil record, it is essential to consider the pollen grain as a functional unit.In the early days of pollen morphology, culminating in Wodehouse's classic Pollen Grains, which was published in 1935, exine morphology was generally studied in relation to intine development and behavior of the wall during changes in humidity of the environment and germination.With the introduction of acetolysis by Erdtman in 1934, attention became focussed more on the sporopollenin skeleton, revealed in intricate detail by removal of cytoplasm, intine, and outer fatty substances.The wealth of information which this method produced was first summarized in the monumental Pollen Morphology and Plant Taxonomy by Erdtman in 1952.While the introduction of scanningelectron microscopy led to an even greater emphasis on the intricate details of exine architecture, transmission electron microscopy, especially when applied to ontogeny, provided a new impetus to the study of the entire grain.Moreover, a renewed interest in the physiology of the living grain (Heslop-Harrison, 1971a, 1971b, 1976) has stimulated an integrated study of all characters, which should ultimately lead to a pollen ecology.When the present contribution, nevertheless, appears to concentrate mainly on the exine, this is because it incorporates a large number of taxonomically important characters which can be easily studied from herbarium specimens and also because, perforce, fossil pollen studies are entirely based on the exine skeleton.Its main purpose is to provide on this base a survey of certain widespread morphological phenomena, to consider their possible functional significance and thus to contribute to a better understanding both of their taxonomic significance and their value for interpreting the fossil record.!The author is much