A major new treatment to the Bryaceae of Europe

The Bryaceae is one of the largest moss families, along with the Dicranaceae, Orthotrichaceae and Pottiaceae. It has long had a reputation for difficulty in species identification, especially in the large and complex genus Ptychostomum. The Bryaceae are distributed worldwide and are well represented in most habitats other than dense forests and the lowland tropics. They often represent up to 10% of the diversity in local and regional floras, and thus cannot easily be avoided in floristic and biodiversity studies despite serious identification issues. It is always a good thing to have a new comprehensive treatment of the family, as there are so few available for most parts of the world. This new book on the Bryaceae by David T. Holyoak treats the family in the western Palearctic, essentially Europe west of the Russian Federation, and including Macaronesia. The eastern limits of the flora treatment include portions of Ukraine, Belorussia, Estonia, Latvia and Lithuania. To the southeast, portions of Turkey are also included. Occurrences from adjacent areas are also included. The hardback book is attractively produced, with a nice cover photo of Ptychostomum pallens in all its pink glory. It is organized into several sections, including the introductory material, several sets of dichotomous keys as well as a multi-access key, species accounts, several appendices, a glossary and an index to all names including full lists of synonyms. I have used the book extensively while preparing this review and it has held up well to repeated use. The text is quite clean, with very few typos. The introductory material includes a short section on classification, including the usual negative comments on my morphologically based classification used in the Bryophyte Flora of North America (Spence 2014). These comments seem to be obligatory as they are repeated in most recent papers on the family by European authors. There is some validity to them, but also significant confusion and misunderstanding of my work. However, this is not the place to discuss these issues; I will present them elsewhere. The introductory sections also include notes on the arrangement and treatment of species, a useful section on characters and hints for identification purposes, and several keys. In all, 69 species are treated in five genera: Anomobryum, Bryum, Imbribryum, Ptychostomum and Rhodobryum. Well-written and clear identification keys are critical to species identification in the family. Holyoak includes a general key that leads to six additional keys, including one to species with mature sporophytes, three keys for species with rhizoidal tubers, leaf axil bulbils, and filamentous gemmae, and a key for sterile collections lacking these structures. The sixth key is a multi-access one based on 10 characters in tabular form. I have tried the keys with various specimens and in general they work well, although I confess that I have not tried the key to sterile specimens. This key is included as a last-ditch attempt to identify sterile specimens, which is always problematic. As Sainsbury noted in his New Zealand flora (Sainsbury 1955: p. 265), ‘‘Scanty and imperfect material is seldom worth