Based on unpublished original material of C. G. Ehrenberg, Monas semen, the basionym of Gonyostomum semen, is lectotypified and the current taxonomic concept of that species, distributed in acidic waters in Europe and North America, confirmed. Its prolonged absence from Berlin waters, from where it was described in the mid 19th century is discussed. G. depressum is shown to be the correct name for a rarely reported green flagellate of worldwide distribution, formerly referred to as Vacuolaria depressa and G. latum. First records from five waters of NE Germany are added to its list of occurrences. The binomials G. intermedium and G. ovatum, of the two other European species of the genus, which are only known from their type localities, are lectotypified.
Willdenowia is an international peer-reviewed journal publishing original research papers in English from the entire fields of plant, algal and fungal systematics, covering the evolution, taxonomy and nomenclature of these organisms as well as related fields such as floristics and plant geography. Three issues appear each year (in April, August and December) in an open-access online edition and a print edition. Individual papers may be published in the online edition as fast-track articles ahead of inclusion in these issues.