This volume of Nova Hedwigia Beihefte includes papers covering a broad range of topics in diatom and chrysophyte research - including historical analyses of taxa names and name changes - through descriptions of novel taxa; observations of fine details of valve and cell morphology and ultrastructure, in many cases in an ecological and/or biostratigraphic context; to attempts at clarifying some hard-to-resolve questions on the evolutionary history of diatoms. Although there is no single common scientific thread connecting all contributions, they are all influenced, in some way, by the work of R. M. Crawford. Some highlight the still substantial extent of undiscovered terrain in the realm of diatom (and microalgal) ultrastructure, regarding variations on the fine construction of both frustules and organic cell components, an area of research in which R. M. Crawford laid important groundwork. Other papers add to our understandingof individual taxonomic groups in which R. M. Crawford raised a heightened interest, such as the genus Corethron which features the most elaborate movements of cell wall parts during cell division in diatoms, or the diverse genera of melosiroid diatoms where the work of R. M. Crawford was instrumental in recognizing the extent of (functional-)morphological and ecological variability.

Combining diverse perspectives and methods, this volume will be of interest to researchers of diatoms, chrysophytes and other microalgal groups.

The volume is dedicated to Richard M. Crawford, who spent a lifetime researching dinoflagellates and diatoms, particularly their morphology and taxonomy, utilizing various microscopical techniques. He is perhaps best known for his pioneering works on the dinoflagellate genera Oxyrrhis and Woloszynskia, and the centric diatoms, Aulacoseira, Melosira, Ellerbeckia, Paralia, and Corethron. He was one of the contributors to the famous blue book (The Diatoms: Biology & Morphology of the Genera) and was the curator to the Hustedt Diatom Collection in Bremerhaven.