摘要:

AbstractThe single germ tubes produced by the spores ofEphemerumcomprise highly chlorophyllose cells divided by transverse cross-walls. All subsequent cross-walls are oblique and thus the protonemata ofEphemerumwould appear to be almost entirely caulonemal. Initially, the protonema comprises a loose mat of irregularly-branched filaments. Subsequently, leading filaments around the margins produce upright determinate branching systems which give the protonema ofEphemerumits distinctive appearance. The ultimate ramifications of these systems terminate in sharp points with thickened walls whilst their regular branching is predetermined by zig-zag development of the young side branches. Unlike all the other parts of the protonema, the determinate branching system fails to regenerate when transplanted onto new medium. Whereas cytokinins stimulate bud formation and cause the formation of highly attenuate filaments, abscisic acid induces the production of chains of mucilage-invested spherical brood cells, a phenomenon also seen in ageing cultures. These are desiccation resistant and germinate rapidly on new medium. Nutrient-free agar has little effect on protonemal morphogenesis.

ISSN:0373-6687    

DOI:10.1179/jbr.1993.17.3.397

出版商:Taylor&Francis    

年代:1993

数据来源: Taylor

摘要:

AbstractThe protonema ofOrthotrichum obtusifolium,regenerated from leafy shoots, comprises a dense mass of largely unbranched exclusively upright filaments. All the cells have transverse cross-walls and contain numerous chloroplasts which become larger and discoidal in older filaments. Differentiation into chloro- and caulonema is absent. When upright filaments are transplanted onto an agar surface, they act as the main axes for a further set of upright branches. Buds and side branches are produced symmetrically at right angles to the mother cells. Protonemal morphogenesis hardly changes on nutrientfree medium and spherical brood cells are not produced after prolonged culture or in the presence of abscisic acid. Rhizoids with oblique septa and pigmented walls arise from the base of gametophores. These revert to protonemata when in contact with nutrient agar.The upright filaments produce terminal and intercalary filamentous gemmae with well defined abscission cells. The latter swell and lose their contents prior to liberation. Cells immediately below the abscission cells produce side branches in acropetal succession. Secondary gemmae arise by percurrent proliferation and gemmae frequently germinatein situ.

ISSN:0373-6687    

DOI:10.1179/jbr.1993.17.3.409

出版商:Taylor&Francis    

年代:1993

数据来源: Taylor

摘要:

AbstractChinese gallnuts are galls that form on tfie-leaves of sumac trees (Rhusspp) in response to attack by aphids in the Eriosomatinae, for which mosses form obligate winter hosts. Walls of the gallnuts may comprise up to 70% tannins and yield compounds of considerable commercial value, notably tannic acid and gallic acid. Gallnut production can therefore have a major impact on the local economy in rural areas of China.At least 14 types of gallnut have been described, each caused by a different species of aphid. A wide range of mosses act as winter hosts. Of greatest importance commercially is the true-horned gallnut which forms onR. chinensisin response to attack bySchlechtendalia chinensis, an aphid that overwinters on members of the Mniaceae, particularlyPlagiomnium acutum. There are six generations ofS. chinensisin each annual cycle. Reproduction is principally viviparous and parthenogenetic, except for a single sexual generation produced after spring migrants fly from mosses to the sumac trees in April and early May.True-horned gallnuts are traditionally harvested from semi-natural woodland on rocky hillsides. Approximately 1-2% cover ofP. acutumis adequate to give high production of gallnuts provided that it is uniformly distributed, and favourable distribution and abundance of the moss is achieved by artificial transplantation. Attempts are being made to produce gallnuts by growing sumac trees in agricultural fields, but success is lirnited by the difficulty of establishingPlagiomniumspp in the fields. One solution is to cultivate the moss in plastic bowls which are kept for most of the year in sheds. In October each year the bowls are placed outside under the sumac trees for several weeks and autumnmigrant aphids fly into the moss colonies. The bowls are kept in the shed during the winter, the moss mat is stripped from the bowls and placed under the trees in April, and spring-migrant aphids then leave the moss and fly to the trees. The moss regenerates in the bowls during the summer. We are investigating the growth and reproductive ecology ofP. acutumas an approach towards increasing gallnut production.

ISSN:0373-6687    

DOI:10.1179/jbr.1993.17.3.421

出版商:Taylor&Francis    

年代:1993

数据来源: Taylor

摘要:

AbstractIn Dutch rich fens, mid-successional stages dominated bySphagnum subnitensare rapidly being replaced by other vegetation, dominated byS. fallax.In both species growth was strongly reduced in more mineral-rich ground water and simulated river water, compared to growth in rain water.Both species were positively affected by added phosphorus supply, whereas added supply of nitrogen did not alter growth rates.Nutrient supply seemed to compensate for the intolerance to high mineral levels inS. fallax:nutrient addition stimulated growth in length in ground water and simulated river water. Such compensation was not found inS. subnitens.Growth in mixed culture positively affectedSphagnum subnitensand negatively affected its successorS. fallax.The success ofSphagnum fallaxin early stages of succession in more eutrophic fens may to some extent be explained by its tolerance to high mineral levels with increased nutrient supply.

ISSN:0373-6687    

DOI:10.1179/jbr.1993.17.3.431

出版商:Taylor&Francis    

年代:1993

数据来源: Taylor

摘要:

AbstractMeasurements of lobe elongation of the thalloid liverwortsPallavicinia lyelliiandPellia epiphyllawere made on shaded streambanks at Silwood Park using a photographic technique. The average cumulative growth ofPallaviciniaover 12 months from 1 August 1989 was 8.7 mm compared to 24.7 mm forPellia. Monthly growth increments ofPallaviciniawere positively correlated with average air temperature and accumulated temperatures (day-degrees) in each period. Growth ofPelliawas unrelated to temperature. Neither species showed a correlation of growth with rainfall amounts or numbers of wet days, probably because thallus hydration is governed predominantly by soil wetness.Pallaviciniaappears to coexist with the more vigorousPelliaby tolerating drier niches than can be endured byPellia.Persistence ofPallaviciniaat this site may be due to the presence of both sexes and frequent colonization of fresh surfaces by spores.

ISSN:0373-6687    

DOI:10.1179/jbr.1993.17.3.439

出版商:Taylor&Francis    

年代:1993

数据来源: Taylor

摘要:

AbstractThe genera of theWarnstorfia-Calliergongroup are revised taxonomically. The following genera are recognized: (1)Calliergon(Sull.) Kindb., withC. cordifolium(Hedw.) Kindb.,C. giganteum(Schimp.) Kindb.,C. megalophyllumMik. andC. richardsonii(Mitt.) Kindb.; (2)LoeskypnumPaul, withL. badium(Hartm.) Paul in Europe andL. wickesii(Grout) Tuom. occurring outside Europe only; (3)Straminergon Hedenäs, gen. nov.,withS. stramineum(Brid.) Hedenäs,comb. nov.; (4)Warnstorjia Loeske,withW. exannulata(B., S.&G.) Loeske,W. fluitans(Hedw.)Loeske, W. procera(Ren.&H. Arn.) Tuom.,W. pseudostraminea(C. Müll.) Tuom.&T. Kop.,W. sarmentosa(Wahlenb.) Hedenäs,comb. nov., W. trichophylla(Warnst.) Tuom.&T. Kop. andW. tundrae(H. Arn.) Loeske in northern Europe andW. luipichensis(Williams) Hedenäs,comb. nov.,andW. pseudo-sarmentosa(Card.&Thér.) Tuom.&T. Kop. occurring outside Europe only. Type material of many other taxa was studied and their generic placement considered, but in many cases the material was too sparse for judging the exact relationships to other species.Calliergon.is defined by the probable synapomorphies‘stem leaves broadly ovate or broadly rounded-triangular’,‘plants large’and‘axillary hairs large, 2-8(-10)-celled’,Loeskypnumby‘often golden brown or coppery brown colour’,‘strongly incrassate cells throughout the gametophyte’,‘early brownish or yellow-brown axillary hairs’,‘weak and comparatively short nerve, also in the perichaetial leaves’and‘few and only slightly inflated and differentiated alar cells’,Straminergonby the autapomorphies‘colour pale green, whitish green or yellow-green’,‘axillary hairs sparse, weak, 1-2-celled’,‘alar groups ovate or broadly ovate, along the basal leaf margin’and‘margin of the perichaetialleaves strongly and irregularly dentate above’andWarnstorfiaby the probable synapomorphies‘stem leaves not decurrent’and‘red colours frequently present’. Additional characteristic features of the genera are also given and the taxonomic position ofWarnstorfia tundrae, which does not fit well into any of the genera is discussed. Finally, the taxonomie position of theWarnstorfia-Calliergongroup is discussed and keys are given for the European species.

ISSN:0373-6687    

DOI:10.1179/jbr.1993.17.3.447

出版商:Taylor&Francis    

年代:1993

数据来源: Taylor

摘要:

AbstractSections of the stems and leaf sheaths of North American, European and Asiatic specimens ofTimmia austriaca, T. megapolitanaandT. norvegicawere examined microscopically to discover useful discriminatory characters for identification purposes. The presence or absence of stereids in the sheathing part of the nerve appears to be a valuable taxonomic character for use in determining otherwise doubtful or unidentifiable sterile material of the sectionsTimmia(stereids present) andTimmiaurea(stereids absent). Similarly, the presence of a continuously thickened layer on the adaxial side of the sheathing lamina appears to be distinctive for T. norvegica. The characteristics of the stem seem to be of no taxonomic importance.

ISSN:0373-6687    

DOI:10.1179/jbr.1993.17.3.481

出版商:Taylor&Francis    

年代:1993

数据来源: Taylor

摘要:

AbstractA check-list of the bryophyte species of the Grand-Duchy of Luxembourg is given and briefly discussed. An appendix deals with infraspecific taxa. The total number of species is 517 (122 hepatics and 395 mosses); taking into account some acceptable infraspecific taxa, this small country has at least 538 different bryophytes.

ISSN:0373-6687    

DOI:10.1179/jbr.1993.17.3.489

出版商:Taylor&Francis    

年代:1993

数据来源: Taylor

ISSN:0373-6687    

DOI:10.1179/jbr.1993.17.3.501

出版商:Taylor&Francis    

年代:1993

数据来源: Taylor

ISSN:0373-6687    

DOI:10.1179/jbr.1993.17.3.503

出版商:Taylor&Francis    

年代:1993

数据来源: Taylor