Pollen terminology. An illustrated handbook

Abstract

The great micromorphological diversity of pollen grains amongst the seed plants is not only a marvel of nature but also a significant tool for plant biologists, especially taxonomists and ecologists. However, with the staggering diversity comes the problem of setting up a consistent and useful terminology to cope with classifying such morphological features. As the authors of this book state, although such categorization is rather artificial it is essential for defining the range of morphological diversity and generating systematic order. The remit of this illustrated handbook of pollen terminology is to provide a collection of the most useful and important terms in palynology and illustrate them by light and electron microscope micrographs. Essentially, this handbook is an updated and beautifully illustrated version of the web-accessible ‘Glossary of pollen and spore terminology’ (Punt et al., 2007). The largest proportion of the handbook is devoted to an illustrated glossary of pollen-related terms, which is usefully split into several parts. These cover the terminology of pollen units, pollen class, shape and size, apertures, ornamentation, the pollen wall and a miscellany of other terms. This glossary section has been produced to high standards, with an excellent lay-out and organization. Every term is exceptionally illustrated, not by just one but by several micrographs, with light, SEM and TEM figures used where appropriate. Usefully, an alphabetical text version of the glossary is included at the back, making it even easier to track down and define palynological terms. Although the glossary alone is comprehensive, copiously illustrated and user-friendly enough to recommend this volume in its own right, the value of this work is enhanced by a series of short, general chapters that cover palynology and its history, an introduction to pollen morphology, a discussion of why categorization is required and an overview of pollen development. From a more practical perspective, the chapters that cover pollen features that can be misinterpreted, controversial or fuzzy terms and methods are particularly valuable. Whilst this volume will be an essential addition to reference libraries, there is no doubt that it will make a regularly consulted addition to the shelves of individuals involved in studying pollen, from those working in palaeobiology, ecology, entomology and plant systematics through to forensic scientists. Using this volume will simplify the procedure of describing pollen morphology from samples under study. Indeed, this volume would have great value in practical classes for students where pollen, pollen morphology and pollination biology is the subject of investigation. Although the authors clearly state that this handbook is not meant to be an exhaustive treatment of the subject, one or two additions would have further enhanced this attractive and practical book. In a few places, notably in the glossary of miscellaneous terms, the labelling in the illustrations of the feature being defined is inadequate, confusing or absent. For example, for tapetum in the glossary (p. 216) the TEM micrographs do not actually label the tapetal layers. The chapter on pollen development could be improved, with a diagram to explain the sporophytic lineage of cells in anther development leading to pollen formation via meiosis. The statement that ‘gametogenesis starts with formation of a central vacuole within the uninucleate microspore’ is both confusing and inaccurate. Strictly, gametogenesis is associated with the second pollen mitosis of the generative cell. Perhaps the most significant omission in this volume is a focused discussion concerning the use of pollen micromorphology in plant systematics. It would have been interesting and informative to discuss particular morphological and developmental features from a phylogenetic perspective. For instance, for each morphological feature an outline of the known pattern of distribution amongst seed plants would have been useful. There is also almost no mention of whether these strikingly different microscopic features are associated with biologically important phenomena, such as the mode of pollen dispersal, the type of stigmatic surface or manner of pollen germination. This kind of discussion would allow a much greater appreciation of which features of the pollen grain are of adaptive value and which have minimal selective value. Without so much as a limited comment of this kind, even if speculative in nature, the diversity of morphological features that are so well illustrated in this handbook become rather abstract and meaningless. Although there are a few shortcomings, this handbook is not only of practical use but also exceptionally well-crafted and a delight to the eye. In the age of online resources, it emphatically demonstrates that well-produced reference books can be superior to web-based material. I have no doubt that this will become an indispensable standard reference work for all scientists studying pollen.