The Habitat of Zygodon forsteri (Brid) Mitt. in the New Forest,Hants

Abstract

Seven species are reported here for the first time for South Georgia. Two of these were already known from Tierra del Fuego, Acrolophozia fuegiana Schust. and Marsupella sprucei (Limpr.) H. Bern., but Acrolophozia sulcata Hässel, Marsupella austrogeorgica Hässel, and Marsupella minutula Hässel are described as new. The additional two species which are described, Austrolembidium crassum Hässel and Greeneothallus gemmiparus Hässel, also required the creation of two new genera. The total number of liverwort species now known to be present on South Georgia is sixty-six.     

The relationship between Mittenia plumula (Mitt.) Lindb. and Schistostega pennata (Hedw.) Web. & Mohr

Abstract

In spite of the absence of a peristome in Schistostega, developmental studies show that the internal structure of the capsule has considerable similarity and presents no strong barriers to a relationship with Mittenia. This is strongly supported by the protonema and many features of the gametophore and sporophyte. Therefore it is suggested that the Mitteniaceae be transferred from the Bryales to the Schistostegales.     

Relationship between Sex Distribution and Sporophyte Production in Pleurozium schreberi (Brid.) Mitt.

The distribution of perigonia, perichaetia, and sporophytesof Pleurozium schreberi has been investigated in Britain andin some other areas. Fruiting populations are widespread ina zone extending from northern Scotland across southern Scandinavia,but are rare in southern Britain, and appear to be infrequentin many other parts of western Europe. Less information is availableoutside western Europe: fruiting collections have been examinedfrom scattered localities throughout much of the species' northerncircumpolar range, but there is no evidence of areas where theyare abundant. The rarity of sporophytes is correlated with a rarity of plantsbearing male inflorescences. Barren specimens normally comprisedonly female and sterile plants, while most fruiting specimenswere bisexual but contained more female than male stems. Femaleplants are abundant throughout Great Britain, but plants withmale inflorescences appear to be widespread only in northernScotland and in East Anglia. The latter area is unusual in thatsporophyte production fails in many bisexual colonies. Sporophyte production was stimulated experimentally by transplantingmale plants from East Anglia into female populations in theWest Midlands. The male plants spread vegetatively within thefemale colonies, and perigonia developed during six successiveyears. At an East Anglian station sporophytes developed aftermaterial was transplanted between unisexual male and femalecolonies only 10 m apart.     

The placenta in Monoclea forsteri Hook. and Treubia lacunosa (Col.) Prosk: insights into placental evolution in liverworts

Placental morphology is remarkably diverse between major bryophyte groups, especially with regard to the presence and distribution of transfer cells in the sporophyte and gametophyte. In contrast, with the exception of metzgerialean liverworts, placental morphology is highly conserved within major bryophyte groups. Here we examine the ultrastructure of the placenta in Monoclea forsteri and Treubia lacunosa, basal members of the marchantialean and metzgerialean liverwort lineages, respectively. In both species several layers of transfer cells are found on both sides of the placenta, with sporophytic transfer cells exhibiting prominent wall labyrinths. Consistent with previous reports of a similar placenta in other putatively basal and isolated liverwort genera such as Fossombronia, Haplomitrium, Blasia and Sphaerocarpos, this finding suggests that this type of placenta represents the plesiomorphic (primitive) condition in liverworts. Distinctive ultrastructural features of placental cells in Monoclea include branched plasmodesmata in the sporophyte and prominent arrays of smooth endoplasmic reticulum, seemingly active in secretion in the gametophyte. These arrays contain a core of narrow tubules interconnected by electron-opaque rods, structures with no precedent in plants. Analysis of the distribution of different types of placenta in major bryophyte groups provides valuable insights into their inter-relationships and possible phylogeny.     

Genetic structure of mosses Pleurozium schreberi (Willd. ex Brid.) Mitt. and Racomitrium lanuginosum (Hedw.) Brid. along altitude gradients in Hokkaido,Japan

Abstract

The families Pterigynandraceae and Rigodiaceae are reviewed for Africa with reference to the collections made by the BBS Expedition to Mt Mulanje, Malawi in 1991. The single African species of Rigodium (Rigodiaceae) is reported to be quite frequent on Mt Mulanje, and three of the four species of Trachyphyllum (Pterigynandraceae) found in Africa (T. gastrodes, T. dusenii and T. inflexum) are reported, the latter two for the first time from Malawi. On present limited evidence, Malawi seems to be a centre of diversity of the genus.