Sporeling development in Cavicularia densa was determined using controlled culture and light microscopy techniques. Ontogeny is typified by endosporic germination followed by early protonematal ...development via the production of a terminal quadrant of four cells which ruptures the spore wall distally. Sporeling production is triggered by the delimitation of a cuneate apical cell in one of the quadrants. Regular apical cell segmentation produces derivatives and adult merophytes that ultimately result in a juvenile Cavicularia gametophyte. The fundamental sporeling pattern exhibited by Cavicularia is shared only with that of its sister genus Blasia. Moreover, the patterns of sporeling and gemma/gemmaling ontogeny in Cavicularia and Blasia share quadrant systems of precise uniformity, thus reinforcing the close relationship between the blasialean genera.
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A working checklist of accepted taxa worldwide is vital in achieving the goal of developing an online flora of all known plants by 2020 as part of the Global Strategy for Plant Conservation. We here ...present the first-ever worldwide checklist for liverworts (Marchantiophyta) and hornworts (Anthocerotophyta) that includes 7486 species in 398 genera representing 92 families from the two phyla. The checklist has far reaching implications and applications, including providing a valuable tool for taxonomists and systematists, analyzing phytogeographic and diversity patterns, aiding in the assessment of floristic and taxonomic knowledge, and identifying geographical gaps in our understanding of the global liverwort and hornwort flora. The checklist is derived from a working data set centralizing nomenclature, taxonomy and geography on a global scale. Prior to this effort a lack of centralization has been a major impediment for the study and analysis of species richness, conservation and systematic research at both regional and global scales. The success of this checklist, initiated in 2008, has been underpinned by its community approach involving taxonomic specialists working towards a consensus on taxonomy, nomenclature and distribution.
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The pattern of gemma/gemmaling ontogeny in the liverwort Cavicularia densa is described from its origin as a primordium within the gemma chamber to the formation of a juvenile gametophyte. Data were ...obtained from field-grown and axenically cultured plants using a combination of light and scanning electron microscopy techniques. The developmental pattern is characterized by the production of a discoid to ellipsoid, stalked gemma composed of distinct tiers of cells, the central rows of which terminate in latently generative margin cells which originate the occasion of plantlet formation. Gemmaling production results from a generative cell (either an adult apical cell, or a gemmaling initial that transitions into an adult apical cell) that arises from a lateral terminal cell subsequent to quadrant formation. Ultimately, the juvenile gametophyte typical of Cavicularia is produced through the activity of an adult cuneate apical cell. Throughout juvenile gametophyte production, subsequent repetitions of select combinations of primary division sequences along with cytological modifications may continue in the gemma proper. Comparisons with the pattern of receptacular gemma/gemmaling development in Blasia reveal that the fundamental pattern of ontogeny within the Blasiales composes the construction of a tiered gemma bearing latently, generative lateral margin cells and a quadrant system containing the production of a wedge-shaped generative cell responsible for gemmaling construction and ultimately the formation of a juvenile gametophyte through adult merophyte development.
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A working checklist of accepted taxa worldwide is vital in achieving the goal of developing an online flora of all known plants by 2020 as part of the Global Strategy for Plant Conservation. We here ...present the first-ever worldwide checklist for liverworts (
Marchantiophyta
) and hornworts (
Anthocerotophyta
) that includes 7486 species in 398 genera representing 92 families from the two phyla. The checklist has far reaching implications and applications, including providing a valuable tool for taxonomists and systematists, analyzing phytogeographic and diversity patterns, aiding in the assessment of floristic and
taxonomic knowledge, and identifying geographical gaps in our understanding of the global liverwort and hornwort flora. The checklist is derived from a working data set centralizing nomenclature, taxonomy and geography on a global scale. Prior to this effort a lack of centralization has been a major impediment for the study and analysis of species richness, conservation and systematic research at both regional and global scales. The success of this checklist, initiated in 2008, has been underpinned by its community approach involving taxonomic specialists working towards a consensus on taxonomy, nomenclature and distribution.
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The pattern of gemma/gemmaling ontogeny in the liverwort Blasia pusilla L. is described from its origin as a primordium within the gemma receptacle to the formation of a juvenile gametophyte. Data ...were obtained from herbarium specimens, field-grown and axenically cultured plants, using a combination of light and scanning electron microscopy techniques. A consistent, uniform, fundamental developmental pattern was elucidated that is characterized by the production, within the receptacle, of a discoid to ellipsoid, stalked gemma composed of distinct tiers of thick-walled cells and margined by lateral columns of thin-walled, potentially active cells. After dispersal from the receptacle, lateral growth ensues from a gemmaling initial that is produced via quadrant formation from one lateral margin cell. Ultimately, an adult cuneate apical cell is honed that generates segments the same as in the adult plant to produce the juvenile gametophyte typical of Blasia. Both the gemmaling and sporeling ontogenies of Blasia incorporate a quadrant system that is fundamental to generative cell formation. However, sporeling ontogeny is reduced as compared with that of gemmaling ontogeny in its lack of a cell comparable to the gemmaling initial, and in its less extensive, less variable basal quadrant segmentation. The existence of similar quadrant stages in the primary ontogenetic patterns of Blasia and the frequency of quadrant production in sporelings of numerous complex thalloid liverwort taxa suggest the need to precisely elucidate the primary ontogenies of these key taxa to allow comparative analyses that will aid in more accurately deducing the phylogenetic affinities of the Blasiales.
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In order to aid in making sound stewardship decisions, Hawk Mountain Sanctuary Association has undertaken a complete biological resource inventory of sanctuary lands. In 1993, the bryophyte component ...of this project began with the cataloging of the bryoflora of public sanctuary sites. The current report expands upon this baseline data by focusing on the bryophyte inhabitants of Hawk Mountain sites to which public access is restricted. Specific sites, reflective of the ecological variety of restricted areas were selected for extensive bryophyte collection. Twenty moss and 4 liverwort taxa were added to the known bryoflora of Hawk Mountain, bringing the total of identified bryophyte taxa to 66; 48 moss species representing 22 families and 12 orders of the division Bryophyta and 18 liverwort species representing 12 families and 2 orders of the division Hepatophyta. Infrequently collected Pennsylvania bryophytes found only on sanctuary sites to which public access is restricted included Diphyscium foliosum (Hedw.) Mohr. Drummondia prorepens (Hedw.) Britt. Hypnum pallescens (Hedw.) P. Beauv. var. pallescens, Leptodictyum riparium (Hedw.) Warnst., and Orthotrichum pusillum Mitt. Drummondia prorepens and O. pusillum are endemic to eastern North America. Other bryophytes of note include Anacamptodon splachnoides (Froel. ex Brid.) Brid., which is of uncommon occurrence throughout eastern North America and the exclusively Appalachian Lophocolea cuspidata (Nees) Limpr. var. alata K. Mull.
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Leucobryum glaucum (Hedw.) Ångstr. protonemata and sporelings were studied in order to determine and describe fundamental ontogenetic patterns. Spores were cultured under controlled, axenic ...conditions and developmental stages were examined using light microscopy techniques that allowed observations in multiple optical planes. Germination is exosporic, followed by a distinct developmental sequence that constructs the basal protonemal assemblage of chloronemal filaments. Extensive branching from side branch initials and transformations of filament types yield a mature, heterotrichous protonema composed of prostrate chloronema and caulonema, a monopodial system of erect chloronemal branches, and thigmotropic rhizoids. Target cells, which form on filaments that are intermediate in type between chloronema and caulonema or on distinct caulonemal filaments undergo a specific, uniform pattern of sporeling ontogeny which is characterized by the production of an apical initial with three cutting faces that segments briefly, then is transformed into an adult obovoidal apical cell. Repeated adult segmentation and merophyte development result in a juvenile L. glaucum gametophyte. Traditionally, Leucobryum sporelings have been classified as representatives of the Bryum type. However, the detailed ontogenetic patterns of L. glaucum protonemata and sporelings reveal characters that not only define Bryum type sporelings, but also Funaria type sporelings. This suggests that more emphasis be placed on the fundamental ontogenetic patterns of protonemata and sporelings as criteria for classifying basic moss sporeling types.
Hawk Mountain Sanctuary is part of the Kittatiny Ridge of the Appalachian Mountain range and lies in the northwest corner of Berks County, Pennsylvania. The nearly 1000 ft. elevation gradient on Hawk ...Mountain allows a variety of topography-dependent habitats for flora and fauna. Although the vascular flora of Hawk Mountain has been documented, the bryoflora has not. In this investigation, the moss and liverwort diversity was examined to establish a baseline for future bryological research. Although collecting encompassed the entire mountain, sampling concentrated on specific sites which reflected the topographic variances. Twenty eight moss and 14 hepatic species comprise the bryoflora of Hawk Mountain, with moss diversity greater in the mid to upper elevations and hepatic diversity greater in the lowlands. Common Pennsylvania mosses such as Brotherella recurvens (Mx.) Fl., Polytrichum ohioense Ren. & Card. and Platygyrium repens (Brid.) BSG are frequent inhabitants, while rarer mosses such as Anacamptodon splachnoides (Froel ex Brid.) Brid. and Leucobryum albidum (Brid.) Lindb. are locally abundant. Tetraphis pellucida Hedw. is of note due to its preference for sandy and peaty soils rather than rotten logs and stumps. Prominent liverwort taxa include the Appalachian endemics Lophocolea cuspidatum fo. alata (Mitt. ex Larter) Schust. and Diplophyllum apiculatum (Evans) Steph.
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