This Festschrift volume in Nova Hedwigia honours Ursula Geissler on her 65th birthday as well as celebrates her outstanding contributions to phycology, both through her published work and her service as editor for 20 volumes of Nova Hedwigia. The 27 papers reflect Geissler's interest in diversity and systematics, particularly in diatoms. The first two-thirds of the volume deals with the phylogeny, systematics, and floristics of diatoms and includes descriptions for two new genera (Asteroplanus and Fogedia), 15 new species, and three new varieties of diatoms, as well as five new combinations. The last one-third of the volume treats systematics, morphology and floristics of a diverse group of microalgae in other divisions, including papers on each of the following: Mallomonas of German eutrophic waters, scaled chrysophytes in Siberia, a new Cryptomonas species, a new Peridiniopsis species, ultrastructure of the rare chlorophycean alga Pachycladella umbrina, the desmid flora of two urban German bogs, the nondesmid phytoplankton community of a highly acidic bog, algal drift in a small mountain stream, and rediscovery of a rare nonphotosynthetic protist, Paramastix conifera. Apart from the three papers on marine diatom taxa, the two papers on new tropical species, and the paper on Siberian chrysophytes, the papers deal exclusively with freshwater microalgae of temperate climates. Furthermore, most of the papers represent Eurasian collections, with 11 from Germany (mostly in the vicinity of Berlin). The papers are all well written and are authored by an impressive collection of well-known and well-respected phycologists from around the world. Six papers are in German; all others are in English. Although all of the papers are of good quality, there are some that stand out as especially noteworthy. Erwin Reichardt's (Nova Hedwigia 65: 99-129) revision of the species cluster formerly included in Gomphonema pumilum is an especially important paper given the relative commonness and confusion surrounding this group. He describes seven new species and two new varieties of Gomphonema, illustrating them with numerous light and some scanning electron micrographs. This will be a critical paper for phycologists working on freshwater diatom floristics. A similarly important paper, though not so extensive, is the comparative study of Achnanthidium by Hiromu Kobayasi (Nova Hedwigia 65: 147-163). Although it deals with only four closely related taxa, the combination of light and scanning electron microscopy and careful drawings demonstrates the differences in a difficult-to-differentiate group of small variable taxa. One hopes that this paper will stimulate a better treatment of other members of this common but still poorly understood genus. I was also impressed by the paper on the new genus Fogedia by Witkowski et al. (Nova Hedwigia 65: 79-98). Not only is a new genus described based on the marine littoral species Navicula giffeniana Foged, but an additional transfer and three new taxa are also described and well illustrated, giving the paper a completeness and thoroughness not always evident in new generic designations. Although not relevant to a large number of diatomists, the paper by Shigeki Mayama (Nova Hedwigia 65: 165-176) on Eunotia valida and Eunotia pseudovalida was exciting to me, because I have seen both and never felt completely comfortable calling the latter E. valida. His paper clearly differentiates these potentially confusing taxa. Two of the diatom papers were especially thought provoking. Medlin et al. (Nova Hedwigia 65: 1-11) date the probable origin of the diatoms using a small-subunit rRNA molecular clock calibration. The origin of not only the diatoms, but also of the pigmented heterokonts, is postulated. According to their analyses, the earliest origin for the diatoms was sometime around the Permian/Triassic boundary (238 to 266 million years ago). This is considerably earlier than the earliest appearance in the fossil record, which was in the mid-Jurassic. The trees generated from the molecular data are also of interest in their own right and demonstrate the need for molecular data in many groups, particularly the naviculoid diatoms, which are not included in the analyses in this paper. The other paper that I found intriguing was the piece by Eileen Cox on subspecific diatom taxa (Nova Hedwigia 65: 13-26). She reviews the historical use of such ranks in diatom taxonomy, defining well the problems and inconsistencies. She then makes a number of pragmatic recommendations for the future use of subspecific taxa. Her guidelines would probably reflect the consensus of the majority of diatomists, but her clear treatment could help bring some standardisation to the creation of species, varieties, and forms. Of the papers on diatom floristics and ecology, two were especially interesting to me. Dokulil et al. (Nova Hedwigia 65: 273-283) examined the water quality of an unusual habitat, an urban floodwater impoundment near Vienna. Their treatment is interesting because the habitat is neither strictly running water nor a lake, and yet the use of indicator diatoms from established indices gave an accurate assessment of the trophy and saproby of this system when compared to other independent measures. Hahn and Neuhaus (Nova Hedwigia 65: 285-298) surprised me with the unusual diatom flora of an agricultural soil. Navicula lacunolaciniata, a taxon previously known only from highly organically polluted rivers was the most common diatom in the soil, a very unusual find. Of the nondiatom papers, there were two that will likely have broad appeal. Gutowski (Nova Hedwigia 65: 299-335) presents distributional, morphological, and ecological data for 29 Mallomonas species from 29 eutrophic localities in Berlin. Weighted means and ranges for temperature, pH, and conductivity are presented. The paper is well illustrated with 89 transmission electron microscopy figures. Scheer and Kusber (Nova Hedwigia 65: 385-409) report on the desmids present in two bogs in an urban reserve in Berlin. Apart from the value of the illustrations and descriptions of the desmids, this paper is noteworthy for its call for the preservation of Sphagnum stands in urban nature preserves. This sentiment reflects Geissler's early insistence that algae be added to the list of endangered species in Germany and that diverse aquatic habitats be preserved for the sake of the algae living in them. Microalgae: Aspects of Diversity and Systematics is an excellent collection of papers on the microalgae. It does not contain experimental ecology or physiology, nor does it have molecular data beyond the paper by Medlin et al. (Nova Hedwigia 65: 1-11). Nothing in the volume struck me as revolutionary or trend setting. For the most part, the papers are good, solid systematics and floristics, research that is appreciated by algal systematists and ecologists who do species specific work in natural systems. I would have liked to have seen a paper about Ursula Geissler herself, including where she got her degrees, with whom she has worked, a list of all of her publications, etc. However, she is certainly honoured by the large number of researchers who wrote excellent papers for her Festschrift. The book will be of greatest interest to diatomists, and if funds are available, I would consider the volume a good purchase for phycologists concerned with taxonomy and systematics of diatoms. It contains a number of papers to which repeated reference will likely be necessary. The book is of less importance to nondiatomists. Certainly it has something of interest for most workers studying freshwater, temperate climate microalgae, but the nondiatom topics at the end of the volume are not taxonomically cohesive, and so the last one- third of the papers will not be relevant as a set to many phycologists. Nondiatom researchers likely will want to obtain copies of selected papers from the volume that are of specific relevance to their research. Jeffrey R. Johansen Phycologia, Vol. 37 (4), 1998, p. 315/316