Seven genera of Thuidiaceae are recognized in tropical Asia and the western Pacific: Thuidium Schimp. (6 sp.), Thuidiopsis (Broth.) M.Fleisch. (2 sp.), Pelekium Mitt. (syn. Cyrto-hypnum (Hampe) Hampe & Lor., 12 sp.) and the monotypic genera Aequatoriella Touw, Bryochenea C.Gao & K.C.Chuang, Indothuidium Touw, and Orthothuidium D.H.Norris & T.J.Kop. Inouethuidium R. Watanabe is excluded. Keys are provided to the genera and species found in the study area. The species are revised, described, and illustrated, and their variability, distribution (illustrated by dot maps), ecology, nomenclature, and typification are discussed. The largest number of species is shared with Africa (6), followed by the adjacent, more temperate part of the Northern hemisphere (3), and Australasia (2). Among the remaining species three are mainly Himalayan epiphytes, four are Malesian tropical lowland rainforest species, and three are endemics from New Guinea (2) or the Society Islands (1). Indothuidium kiasense (R.S.Williams) Touw is confined to areas with a pronounced seasonal climate. The two species known from Hawaii (Thuidium cymbifolium (Dozy & Molk.) Dozy & Molk. and Pelekium versicolor) are among those widespread throughout the study area. Several names in common use for Thuidiaceae from Asia, Africa, or the temperate part of the Northern hemisphere are reduced to synonyms. Thus, Northern hemisphere Thuidium philibertii Limpr. and African T. matarumense Besch. are reduced to synonyms of Himalayan T. assimile (Mitt.) Jaeg., Asian T. tamariscellum (Müll.Hal.) Mitt. and T. sparsifolium (Mitt.) Jaeg. become synonyms of African Pelekium versicolor (Müll.Hal.) Jaeg., and Asian Thuidium kuripanum (Dozy & Molk.) R.Watanabe and T. trachypodum (Mitt.) Bosch & Sande Lac. become synonyms of African Pelekium gratum (P.Beauv.) Jaeg.

  The Lejeuneoideae are shown to be a well-defined group, best circumscribed by the 12+4 seta type and the J-shaped insertion of the leaves. With two exceptions (Aureolejeunea, Ceratolejeunea) they have lost capacity to form gametophytic wall pigments. Their explosive diversification is assumed to have been stimulated by the mid- to late-Cretaceous spread of dense, humid angiosperm-dominated forests, which resulted in the creation of numerous new niches, from leaf surfaces to twigs to tree trunks. With the very temporary nature of some of the niches exploited, competition was seemingly reduced when not excluded as a factor. Evolution thus tended to be explosive and sometimes seemed random.

  This, in at least part, accounts for the extraordinary diversification, where in any one niche, numbers of seemingly ecologically equivalent taxa may succeed. Thus, probably from mid-Cretaceous time on, some 60 or more genera of the single subfamily Lejeuneoideae arose and diversified. Some, existing in “temporary” environments, behave much like ephemerals among Angiosperms.

  The extraordinary mass of taxa has shown parallel reduction and simplification of the sporophyte, with reduction of (and eventual loss) of elater spirals; reduction in elater numbers; reduction and loss of stiffening localized bands in the capsule wall. These simplifications occurred repeatedly as parallel adaptations to a humid/moist sheltered environment in which spore dissemination by wind often was no longer effective.

  With adaptation to a milieu where more passive spore discharge was the norm, and with obsolescence of the elater spiral, and of significant thickenings in the capsule wall, capsule valves lost the capacity to spread widely; the valves remained erect. It is assumed this adaptation occurred several times.

  The 60 or more genera are placed into some nine tribes, in each of which some of the adaptations to a tropical/semitropical forested environment were adopted. The numerous evident parallelisms (and lack of adequate sporophyte data) are admitted to be serious impediments to evolution of a satisfactory tribal classification. These problems are repeatedly discussed.

  Current classification of the New Zealand hepatic Neogrollea notabilis Hodgs. in Lepidoziaceae and in Suborder Lepidoziineae is discussed. Recent discovery of the gynoecium and sporophyte, together with detailed morphological studies of the gametophyte, show that Neogrollea is beyond the circumscription of the Lepidoziaceae. The genus is therefore placed in a new family, Neogrolleaceae. The new family possesses a number of characters that will exclude it from Suborder Lepidoziineae, and a new suborder, Subord. Neogrollineae, is created for it. Placement of the Neogrollineae as the basalmost perianth-bearing member of Jungermanniales is discussed and proposed.

  Leptoscyphus Mitt. is represented in southern South America by L. chilensis (De Not.) Hässel n. comb., L. antarcticus (C. Massal.) Solari, L. magellanicus (Gola) Hässel n. comb., L. huidobroanus (Mont.) Gottsche and L. chiloscyphoideus (Lindenb. ex Lehm.) Gottsche; all these are here described, illustrated and distinguished with a key. Leioscyphus patagonicus Steph., Lophocolea aromatica Steph., Chiloscyphus supinus β assimilis C. Massal., Lophocolea angulata Steph., Mylia pseudorepens Herzog and derived names are synonyms of Leptoscyphus chilensis (De Not.) Hässel; Leptoscyphus monoicus Solari is a new synonym of Leptoscyphus magellanicus (Gola) Hässel and Leptoscyphus hatcheri Fulford is a new synonym of Leptoscyphus chiloscyphoideus (Lindenb. ex Lehm.) Gottsche. Leptoscyphus expansus (Lehm.) Grolle is excluded from the area. The distribution of the species is extended through citations of specimens examined.

  There are approximately 65 taxa from the liverwort genus Frullania that have been reported for the Australian botanical region. This study discusses aspects relating to five Frullania species, including features associated with the sporophyte which have not previously been investigated. First, we report F. incumbens as a new record for Australia; second, we re-evaluate the taxonomic status of the F. pentapleura species complex; Frullania wildii is subsequently reduced to a synonym of F. pentapleura, and both F. pentapleura and F. probosciphora are recognised at the species level. Finally, notes are provided for F. apiculata and F. hypoleuca; two widespread but poorly described species.

  The oil bodies of 22 species belonging to 18 hepatic genera from Singapore are described, photographed, and discussed. Oil bodies of 11 species are described for the first time.

  Ditrichum tortuloides Grout from the eastern United States has been considered a synonym of D. ambiguum Best from the western part of North America, however, the present study reveals they are closely related, but distinct species.

  Weymouthia cochlearifolia is revised and illustrated. W. billardieri (Hampe) Broth. is a new synonym. New synonyms, Meteorium molle Wils. var. majus Wils. and Pilotrichella mollis (Hedw.) Jaeg. var. major (Wils.) Jaeg., are reported for W. mollis. Altitude-latitude figures are presented for both species together with a discussion of their distributions and habitat preferences.

  Ten new moss records, including six species of Calymperaceae, are reported for Vanuatu as well as 17 species new for either Efate or Espiritu Santo, with the majority for Efate. Splachnobryum novaeguineae, previously known as an endemic of Papua New Guinea, is new to Vanuatu.

  Floristic or gamma diversity of bryophyte vegetation was studied for fifteen islands scattered on the adjoining sea of Nagasaki Prefecture, southwestern Kyushu, Japan. A total of 167 bryophyte species (118 mosses, 47 liverworts and 2 hornworts) were observed on the islands. A positive correlation was seen between the area of islands studied and the elevation. But the most highly positive correlation was seen between the area and number of species. The regression equation was log y=0.373 log x+4.212, where y is the predicted number of species and x is the area (km²). The correlation coefficient was 0.989. Similarly, a highly positive correlation was seen between the area and number of life-forms.

  Numerous collections representing 183 species of lichens, ascomycetes and lichenicolous fungi are reported from gatherings made in Hong Kong in July 2000, mainly on Lantau Island. These include 9 species which are described here as new to science: the lichenized ascomycetes Anisomeridium tetrasporum, Biatorella saxicola, Ocellularia palaeoamplior, Ramalina seawardii, Ramalina throwerae, the non-lichenized corticolous ascomycete Granulopyrenis seawardii, the lichenicolous ascomycete Obryzum striguloides, and the lichenized hyphomycete Milospium planorbis, one of the very few lichenized hyphomycetes known. It is argued that Reichlingia leopoldii similarly represents a lichenized hyphomycete rather than a lichenicolous fungus on an unknown host. The genus Campsosporiella is synonymized with Anisomeridium and the species Campsosporiella deightonii with Anisomeridium throwerae. In addition, 42 species are newly recorded for Hong Kong, of which 38 are also new to China, 7 new to Asia and 4 new to the Northern Hemisphere.