Lewis, Walter H., Prathibha Vinay, and Vincent E. Zenger, 1983

Reviewed by Alwynne B. Beaudoin, Department of Geography
University of Western Ontario, London, Ontario, Canada in CAP Newsletter 8(2):16-17, 1985.

The publication of a new book related to pollen is a welcome event and Airborne and Allergenic Pollen of North America is certainly a valuable addition to the literature. Although "written primarily for allergists and others in the medical profession and for aerobiologists" (p. ix), the book contains much material hat should also prove useful to Holocene palynologists. The authors point out that "because there is no comprehensive North American flora ... basic botanical data involving species distribution, flowering times, and taxonomy are not readily available" (p. ix). This book represents a commendable attempt to remedy this deficiency by bringing "together a large amount of divergent, yet relevant, information" concerning plants "whose pollen becomes airborne" (p. xi). This is accomplished by emphasizing visual presentation, mainly photographs, photomicrographs, and maps, "thereby allowing the user an opportunity to assimilate rapidly botanical facts on plant morphology, geography, phenology, and palynology" (p. ix).

Following an introduction, the major part of the book is organized into three chapters: Chapter 1 deals with trees and shrubs, Chapter 2 is concerned with grasses and grass-like plants, while Chapter 3 covers weeds and herbs. Many plant families are discussed: Chapter 1 comprises 52 families of trees and shrubs, Chapter 2 deals with 7 families, and Chapter 3 covers 16 families. Generally, within each chapter, the entries are arranged in alphabetical order by family. Some entries also include discussions at the genus level; these are also arranged alphabetically. However, in Chapter 1, Gymnosperms and Angiosperms are arranged separately; in Chapter 2, Poaceae is the first entry, followed by other grass-like plants, while in Chapter 3, Pteridophytes are discussed first, followed by other weeds and herbs.

For each family, the entry consists of a description of the main botanical features of the family, a list of the main genera, a discussion of flowering and pollen production, a description of the pollen morphology and a discussion of allergenicity. In addition, most entries are accompanied by photograph(s) of one or more species within the family, usually illustrating the flowers or staminate cones. Some of these are also illustrated in colour plates in a separate section near the beginning of the book. In some cases, the entries include maps showing the distribution of numbers of species within a selected genus. The entries also contain both light-microscope and scanning electron microscope photomicrographs of some representative pollen types. These photographs and photomicrographs in particular are one of the best features of this book. Generally, the images are large and very clear. The photomicrographs obtained by light microscopy are most impressive.

The volume contains two appendices. Appendix 2 consists of notes on the preparation of samples and on photographic techniques and equipment. Appendix 1 comprises 735 maps showing "generalized distributions of important wind-dispersed species indigenous to North America" (p. 177). The authors point out that many of these maps are original contributions. For grasses and grass-like plants, the distributions of introduced species are also mapped. For other plants, introduced species are simply listed, together with their "zone of hardiness", which gives and indication of how far north and/or west the species might flourish. The scale of the maps (c. 1:96,000,000) is such that great detail in the distributions cannot be displayed. Nevertheless, this sections does comprise a valuable compendium of distribution data.

Despite the tremendous scope of this book, I have some doubts about how it might be employed. Near the beginning of the book, there is a four page section containing 136 colour photomicrographs described as a "visual key to major pollen types" (p. 5). The quality of these images is not as good as those throughout the rest of the book; many of these photomicrographs seem rather fuzzy. Although the idea of having pollen types illustrated adjacent to one another for comparison is a good one, many of these images are too small to show morphological features clearly. The book lacks a descriptive key to supplement the photomicrographs and the descriptions in the text. Therefore, it would probably not be very helpful in the laboratory for the identification of pollen types while counting. Hence, initial identification of pollen would still have to be undertaken using other sources, such as pollen keys and/or reference material. However, once the pollen is identified, this book contains a large amount of supplementary information that might be beneficial in the interpretation of pollen assemblages. In particular, for many taxa, details of flowering times and modes of pollination are discussed. This kind of data is often difficult to obtain.

One drawback does arise from the authors’ attempt to be thorough and wide-ranging, namely, that little attention can be paid to the subtleties of pollen variation within each taxon. For example, less than two pages is devoted to a discussion of the Pinaceae. No attention is paid to the distinction of pollen of the Pinaceae below genus level. Since pollen from Pinaceae is apparently not a major allergen, this discussion is presumably detailed enough for the book’s targeted readers. For other major allergens, the presentation is more detailed. For example, about 14.5 pages is devoted to a discussion of the Asteraceae. From the point of view of the Holocene palynologist, this lack of detailed discussion within some taxa may be a limitation.

As a minor quibble, the book claims to be North American in scope, but most of the maps extend only as far as c. 60°N (about the latitude of Churchill, Manitoba). Does this reflect a lack of suitable information for the Arctic flora?

On the positive side, the production of the book is excellent. It is printed on a high-quality, glossy paper, and therefore the text is easy to read and the black and white photographs and photomicrographs are clear and crisp. In conclusion, I would say that this book would be a good supplement to a palynologist’s library, since it does contain useful information and illustrative material which is not so readily available and accessible elsewhere.