70 THE TASMANIAN NATURALIST BOOK REVIEW Freshwater Algae in Australia: A guide to conspicuous genera by Timothy Entwisle, Jason Sonneman and Simon Lewis Published by Sainty & Associates, 1997 Softcover$36.95, Hardcover $49.95 Reviewed by Gustaaf Hallegraeff, Department of Plant Science, University of Tasmania. The freshwater algae of Australian lakes and streams are vital indicators of the environmental health of these important aquatic ecosystems. Nutrient pollution and human interference with river flows can lead to toxic cyanobacterial (blue-green algal) blooms which affect the utility of these waters for human or animal drinking purposes. Similarly, macroscopic filamentous algae ("green slime") can choke rivers and channels resulting in aesthetic and economic damage. Over 3000 species belonging to 120 genera have been catalogued from Australian freshwaters (Day et al. 1995) and hence it is fully understandable that only a small selection of organisms could be covered in "Freshwater Algae in Australia ". In this attractively produced booklet (242 pp.), the authors who are associated with the Melbourne Botanical Gardens (Entwisle, Lewis) and Monash University (Sonneman) present over 300, mostly high-quality, colour photographs belonging to 96 genera. This is the first portrait gallery of freshwater algae from the Australian region. It is regrettable that genera are often exemplified by a single species. Important algal divisions such as the diatoms are covered by 6 genera only (Acanthoceras, Aulacosira, Cyclotella, Fragilaria, Gomphonema, Urosolenia), among which the omission of common and important genera such as Navicula and Nitzschia is especially misleading. Similarly, the dinoflagellates are covered by the description of a single genusPeridinium, although pictorially Ceratium and Gymnodiniumare also included. By contrast, filamentous members of the red, brown and blue-green algae, often poorly described in other texts on freshwater algae, are dealt. with in an admirable fashion. Computer generated icons along the right and bottom margins of each photographic plate represent the gross morphology (single cells, motile, filamentous) and indicate at a glance whether the organism is macroscopic or microscopic, that is, visible by low power hand lenses or high power light microscopes. While this presentation and categorisation has its merits, the icons are too large (covering nearly 30% of the space occupied by the colour plates) thereby seriously detracting from the beauty of the micrographs. Another confusing result of such categorisation is that genera appear neither in alphabetical order nor do they cluster logically within algal groups. For example, the diatom Cyclotella (being a