The content of the contributions to this volume is diverse, and deals with morphology, taxonomy, distribution, and ecology of bryophytes.

During the last 20 years much attention has been given to the morphology, development, and phylogeny of the liverwort Treubia, which occupies a pivotal position as one of the lineages in the first diverging clade in phylogenetic reconstructions of the Marchantiophyta.
The important patterns of spore germination and sporeling development, while known for such genera as Haplomitrium, Fossombronia and Monoclea, had heretofore not been studied in Treubia. Crandall-Stotler & Bartholomew-Began (p. 57–66) found that, in fact, the early stages of sporeling ontogeny of Treubia resemble those of these three genera, but that there are considerable developmental differences among the taxa beyond the nine-celled stage of the sporelings. The early stages of germination and sporeling development, as well as apical cell formation, are nicely illustrated with line drawings and scanning electron micrographs. Molecular data helped to uncover or elucidate several unattended problems in various taxonomic groups and ranks. In one of them (Larraín et al.,p. 97–108), they were necessary even to suggest correctly the familial placement of a moss newly discovered in the Andes Mountains of central Chile and in the Falkland Islands. The extremely reduced morphology in both sporophytic and gametophytic traits could perhaps only unequivocally assign the species to the subclass Dicranidae, but molecular data convincingly pointed towards the poorly understood family Rhabdoweisiaceae. The authors provide a very useful and detailed analysis of the genera currently assigned to the family, and established a new genus, Notocynodontium, for their new peculiar moss. Two of the papers touched on generic delimitations: Kučera & Hedenäs (p. 165–178) revisited the genus Campyliadelphus and found that while the type species, C. chrysophyllus, should be merged with the genus Campylium, another currently accepted species, C. elodes has stronger affinities with Cratoneuron and Palustriella, necessitating the erection of a new genus, Kandaea, for C. elodes, and honouring thus the author, Hiroshi Kanda, who contributed significantly to the knowledge of Campylium-like species in the 1970s. Kučera et al. (p. 273–292) investigated the molecular affinities of two pottiaceous species recently recorded in Asian Russia, Bryoerythrophyllum sollmanianum and Tortula yuennanensis, and found again, how deceiving the superficial morphological similarities can be: While the latter species was found deeply nested in Bryoerythrophyllum and had to be combined into that genus (albeit with a new name, B. chenii), B. sollmanianum was found completely unrelated to the rest of Bryoerythrophyllum taxa, and a new genus, Pararhexophyllum, had to be described for it, acknowledging the molecular-phylogenetic affinities to the Central- and South American monospecific genus, Rhexophyllum. Ignatov et al. (p. 243–264), revisited a well-known genus, Fontinalis, which, however, harbours a suite of taxa difficult to delimit in both morphological and molecular way. Plants earlier referable to F. antipyretica var. gracilis were found to occur in two lineages; Asian specimens are referred to a resurrected species, F. perfida, while the European and West-Asian plants are retained a varietal rank within F. antipyretica, albeit with an older name, F. antipyretica var. minor. The unresolved relationships of some “small” taxa recognised by some authors and the nested position of F. squamosa within F. antipyretica s.str. awaits further taxonomic novelties in this group in the near future.

Molecular data are also used to gain new insights into taxonomy and systematics of liverworts.

Gradstein (p. 81–96) used both new molecular and morphological results in his review of the changes of classification of Lejeuneaceae genera in Tropical America since 2001. A major new classification was published in 2013, which has been further refined thereafter. Six new genera are described or resurrected while 24 genera are synonymized with other genera or excluded from the Neotropics in this period. Mamontov et al. (p. 201–242) used molecular methods to investigate the systematic relationship within what used to be named Frullania subsect. Inflatae and found that taxa that previously were classified in the subsection were distributed among three distinct lineages. The majority of species formed a clade that they describe as a new subgenus, subg. Frullaniopsis. Four species (F. cleistostoma, F. saxicola, F. takayuensis and F. wrightii) are resurrected, and three species (F. austinii, F. neomexicana and F. pseudoinflata) are described as new to science. Aguero & Hassel (p. 317–324) clarify the systematic position of the genus Lophochaete. Prior to the advent of molecular studies, and based on detailed morphological studies, the genera Pseudolepicolea and Lophochaete were often considered among the basal lineages of leafy liverworts. To support that argument various authors often stressed the simple plant architecture, in particular the striking triradial symmetry of both the sterile plant and the gynoecium. During this pre-molecular period, Pseudolepicolea and Lophochaete> were often placed in the family Pseudolepicoleaceae or in Blepharostomataceae. Moreover, some authors recognized both genera, while others considered Lophochaete a synonym of Pseudolepicolea.
Molecular studies dramatically altered the disposition of these genera: Pseudolepicolea was placed in the suborder Lophocoleineae, and a species included in Lophochaete, L. trollii, was relegated to an altogether different suborder, Jungermanniineae. The study of Aguero and Hassel provides molecular data that show the phylogenetic position of the type species of the genus Lophochaete (Lepicolea fryei), providing evidence for recognizing Lophochaete as a genus (as a sister lineage to Anthelia) within the family Antheliaceae of suborder Jungermanniineae. Long & Crandall-Stotler (p. 109–116) describe a new species of Marchantia (M. platycarpa) from China. The new species is the third one in the newly recognized subgenus Preissia and the authors compare it with the related M. quadrata that also occurs in SE Asia. While M. platycarpa is only known from the type locality, M. quadrata is widely distributed in the world with several new localities reported here from the Sino-Himalayan region. Engel (p. 265–272) deals with the presence, identity, and nomenclature of the simple thalloid species Pallavicinia lyellii in the New Zealand flora. This name had been used in the New Zealand literature until R. M. Schuster in 1991 commented that New Zealand plants regarded as Pallavicinia lyellii are not the true P. lyellii, a plant from temperate-tropical areas. Schuster introduced the name Pallavicinia pseudolyellii for the New Zealand plants, but that name was invalidly published according the ICBN. Engel here documents the differentiation between these two Pallavicinia species and validates P. pseudolyellii, a plant endemic to New Zealand.

Tamás Pócs devoted a considerable portion of the early years of his long career on research dealing with the Asian representatives of Bazzania, particularly of Vietnam. It is both interesting and noteworthy that Pócs (p. 159–164) establishes that Bazzania vietnamica, a plant that he described in 1969, is conspecific with Bazzania aurescens Spruce of the Neotropics. At the same time this provides another example of liverwort species with a tropical Amphi-Pacific distribution. In addition, Pócs refines our knowledge of Caribbean species of Bazzania, especially the B. pycnophylla complex. The text is nicely buttressed by useful photographic images of specimens.

There are four papers reporting on the occurrence and distributions of bryophytes in areas from the Arctic, the Mediterranean, Sino-Himalaya and the Tropics. Konstantinova & Savchenko (p. 179–192) visited Prins Karls Forland on Svalbard and found 40 liverwort species among the 200 specimens collected during the 10-day expedition. One species, Lophozia fuscovirens, is reported as new for the whole Svalbard Archipelago and the occurrence of one species, Saccobasis polymorpha, that was earlier only reported with a question mark, is confirmed. The bryophyte flora of the Balkans has been studied intensively during the last decades. However, there are still many areas that are poorly known. Papp et al. (p. 117–132) report the results of a visit to Galičica National Park in North Macedonia, the bryologically least known country in the Balkans. They found 179 taxa, out of which 21 are rare and of conservation importance. Some areas in SE Asia, especially in Indochina, are bryofloristically poorly known. Nele Ingerpuu visited Cambodia and made a small collection and found seven liverwort species new to the country. Those reports are included in the checklist of liverworts and hornworts for the country (Ingerpuu et al. p. 293– 316). The list serves as a basis for future studies of the country but includes only 138 species, which is very low for a tropical country, indicating a significant potential for new discoveries. Bai et al. (p. 193–200) undertook to re-examine the geographic range of Porella pinnata, the type species of Porella, one of the larger liverwort genera. Specifically, the objective of their research was to evaluate presence of P. pinnata in Asia. Previous reports of the species for Asia were based on collections from China and India. Their thorough study found that specimens previously reported as P. pinnata in China are actually misidentifications of no less than seven other species of the genus. Yang Bai et al. could not study material from India but conclude that reports from there must be re-examined.

Piotr Górski, a passionate hepaticologist who spent an immense amount of time in the last more than a decade in the cross-border, Polish-Slovak mountain range Tatra Mountains, compiled a modern, IUCN criteria-based Red List of liverworts recorded from this area (Górski p. 67–80). Some 194 species were recorded, of which only four are currently regarded regionally extinct, which is perhaps the best proof of Piotr’s floristic activity and competence. Peterka et al. (p. 133–158) analysed the vegetation affinities of four rare “umbrella species” of rich fens across four European regions, the Alps, Central Europe, the Baltic region and Fennoscandia. They found that their sites were generally more nutrient-rich in Central Europe and the Baltics, and that the Baltic sites also had higher pH. They speculate that the partly different vegetation affinities of these species in temperate Europe could be related to the more severe habitat deterioration and competition pressure, leading to, e.g., increased nutrient availability or decreased habitat connectivity.