Sporopollenin layers present in cell walls of coccal green algae are responsible for their resistance to destructive processes during fossilization as well as during chemical preparation of samples for pollen analysis. Pollen samples of limnic sediments thus often contain abundant algal remains, especially remains of Pediastrum species. Despite their potentional value for environmental and palaeoclimatic reconstructions, such finds have not been paid systematic attention by pollen analysts in the past. The reason for this lack of interest was definitely the virtual absence of simple identification keys and often unclear taxonomy as well as unambiguous species nomenclature.

The present book by KOMAREK & JANKOVSKA represents a long-expected starting point in comprehensive evaluation of Pediastrum remains for the purpose of palaeoecological research. It summaries the experience of two leading scientists, a systematic algologist and a paleoecologist, with the material found in fossil and recent sediments at different geographic situations, i.e., different altitudes, latitudes and longitudes. The contemporary knowledge of ecological requirements of individual Pediastrum species is completed by information derived from their fossil finds. The main merit of this book is to build an interdisciplinary link to species taxonomy, ecology and palaeolimnology with the goal to reconstruct the trophic and temperature conditions of past water ecosystems. Pure algological systematicists may miss detailed classification of several problematic taxa, but the interdisciplinarity and straightforward character of this pioneering work are the main values, according to my personal view as a palaeoecologist.

The contents of the book are divided into three main parts. The first concerns species cytology, life cycle, morphology of the cell wall, and recent ecology. The second part contains a well-elaborated key to identification into species and, if needed, into intraspecific level. The key is richly illustrated using instructive drawings and SEM micrographs. In these, discrimination characters are indicated by arrows. The last, most innovative part, concerns palaeoecological implications of Pediastrum species. It is based largely on original data. Subfossil coenobia are pictured on quality photomicrographs. Proportion between individual parts is balanced, subordinating one's interest to the main scope.

Due to the lack of systematic attention to the subject in the past, the present book is undoubtedly Incomplete in many respects. Despite this bad circumstance, it represents a solid body of up-to-date knowledge to be used by future palaeoecologists and palaeolimnologists. According to my opinion, more research is needed to evaluate the role of azonal microhabitats (seasonaly warm littoral parts of arctic water pools, hot/cold underwater springs of many lakes in different climatic situations; to put at least some examples) in reproduction of Pediastrum populations. Such azonal environments may disturb the geographic distribution patterns of the species and thus may eventually alter with palaeoclimatic reconstructions. We can only expect the raise of interest among limnologists and palaeolimnologists, to whome the book by KOMAREK & JANKOVSKA is highly stimulative.

P. POKORNY

Algological Studies 104

It is not an every day task to prepare a book on the implication of a planktic alga for palaeobotanical research, nor is it an easy task for a phycologist to write a review of such a book. Micro-organisms like diatoms and chrysococcoliths are often used as micropalaeontological indicators, but the identification and evaluation of Pediastrum species is still not an integral part of palynological analysis.

The publication is mainly intended for palynologists, but it starts with a scholarly introduction on taxonomy, cytology, life cycles, cell wall structures, ecological characters and recent distribution of Pediastrum species. This is followed by a paragraph on fossil remains and history. The 24 species of the genus that are well defined and taxonomically justified can be keyed out on the basis of morphological species characters and for each of these species the correct name and first publication date is given, together with any synonyms, a description, notes, figures, and a detailed review of its varieties, their nomenclature and characteristics. The ecology and recent distribution of each species are also dealt with, while palaeontological implications are separately discussed.

Algae and their parts are common and important components of palynological spectra from lake and pond sediments. Characteristic sporopollen in cell wall remnants are commonly present in peaty and lake limnic sediments and occur in palynological slides, even after application of drastic preparations before analysis. However, no special preparation methods have been developed to separate algae from the sediment without much damage. The various species of Pediastrum are ecologically distinct and can serve for ecological characterisations in Late Glacial and Holocene lakes and mires. When using the identification key, the additional data, and the plates of fossilized coenobia, the composition of the whole Pediastrum spectrum can be ascertained to help to prepare for palaeoecological reconstruction of the aquatic environment. In that way phycologists and palynologists can fruitfully cooperate.

It is hoped that this well-prepared book will be instrumental in making analysis of Pediastrum remains part of the integral analysis of palynological samples.

WLEEM PRUD HOMME VAN REINE

Blumea vol. 48, no. 2, 2003, p. 288