Mark Lawley (Ludlow, Shropshire): The Border Bryologists and the British Bryological Society
The Border Bryologists meet to look for and identify bryophytes in Shropshire, Herefordshire, and east Wales. We found it easy to start up our group because the Herefordshire Botanical Society was already providing a forum for active local botanists, to whom we could advertise. And since the Border Bryologists have come into existence, the Shropshire Flora Group has constituted itself into the Shropshire Botanical Society, which also advertises our activities to its members. So, with free advertising and postage provided by two local botanical societies, the Border Bryologists enjoy negligible running costs. Long may our two sugar-daddies remain solvent.
Why have a local group? What purpose does it serve? We wanted first to learn how to identify bryophytes in the field, which necessitated regular meetings close to hand, with an accomplished bryologist in attendance. During our first two years (1994 and 1995) Roy Perry attended nearly all our meetings, and provided the required expertise. Without Roy we would have struggled to identify the plants we found, and quite likely lost heart. Instead we gained sufficient momentum for lift-off. Latterly, Ray Woods and Jonathan Sleath have given expert help, despite busy professional careers. Gradually, the other members of our group have gained in confidence (if not in competence), even though it sometimes seems that the partly sighted are leading the blind.
And what of our future? Rather than allow our group to become a coterie of experienced bryologists, too daunting for beginners to join, those of us who have acquired a little bryological knowledge are trying in turn to help novices gain some bryological ability. Indeed, our most important function is to help interested but ignorant botanists gain a foothold on the lower rungs of cryptogamic competence. Collecting and compiling records for a site or grid-square, and finding uncommon species, are of secondary importance at our arranged meetings, and better catered for during ad hoc or solo sorties.
To further this educational gearing, the Border Bryologists have arranged an indoor workshop at Ludlow Museum this winter. Both the Museum and the bryologists stand to gain. The Museum benefits because getting more people in through the front door this year brings a bigger grant from local government next year. Consequently we have not been asked to pay to hire the museum’s facilities. And budding bryologists will also benefit by acquiring confidence in examining and identifying bryophytes under the microscope: how to dissect leaves off stems, look for auricles on Plagiothecium stems, prepare peristomes for examination, search for stomata on Orthotrichum capsules, or for gemmae and gametangia.
So by getting beginners started – both in the field and indoors – an active Local Interest Group may serve a different function to that of the British Bryological Society. A local group is better placed than the BBS to cater for beginners, who are more likely to become aware of and attend local meetings than make the effort to travel long distances for national meetings. In this way a local group can act as a nursery for L-plate bryologists, who may subsequently join the BBS and the national scene. Indeed, several people from the Welsh borders have recently joined the BBS, apparently as a consequence of interest generated locally.
On the Welsh borders, as elsewhere, local natural history societies and wildlife trusts arrange meetings quite independently of each other, and indeed often seem entirely ignorant of each other’s programmes. I certainly met with genuine rather than merely polite surprise and interest when mentioning the Border Bryologists to local wildlife trusts, and improved communication between groups of local naturalists may well bring more potential bryologists on to the scene. The Worcestershire Wildlife Trust has recently expressed interest in the Border Bryologists as a convenient local vehicle for introducing their members to bryology. At present, no one regularly records bryophytes in Worcestershire, and it will be interesting to see if anything develops in the county as a result of the Trust’s initiative. I suspect that members of other local wildlife trusts would like to learn about bryophytes, but that neither the Trusts nor their members know who to approach locally, and understandably blanch at the prospect of going it alone.
By regarding local groups as nurseries for budding bryologists, one sees the role of our national bryological society in a new light. The British Bryological Society is better placed than local groups to promote bryology to a wider public. My tip as top priority for the BBS’s publicity arm in the coming century is publication of a popular, user-friendly field guide to genera of British and Irish mosses and liverworts: a guide with life-like drawings of the forms of bryophytes and any of their other characteristics which are visible through a lens, while leaving microscopic details for Floras which distinguish species. Its key might also have line-drawings instead of (or at least, as well as) polysyllabic tongue-twisters. The guide would also have distributional and habitat notes as in the three-volume Atlas of the Bryophytes of Britain and Ireland.
A well-produced field guide to genera of British bryophytes could not fail to become the BBS’s flagship publication, and would do far more to attract the public to bryology than any coffee-table book or symposium volume of abstruse scientific articles. Bookshops abound with popular guides to vascular plants, birds, mammals and insects. It is time bryophytes joined them. The Border Bryologists will certainly find it much easier to introduce beginners to bryology once we have a good field guide to take out with us on our excursions.
Border Bryologists, 1999-2000 Copies of our programme are available from Mark Lawley (address below).
The Bygone Botanists of Herefordshire traces the social and personal histories of botanists who explored Herefordshire, with accounts of several accomplished bryologists, including Augustin Ley, Eleonora Armitage and Charles Herbert Binstead.
A Botanical Stroll through North Herefordshire describes the plants of interesting botanical sites in the countryside between Ludlow, Leominster and Presteigne, with annotated lists of bryophytes and vascular plants.
Tom L. Blockeel (Sheffield): Notes from a tourist in Mediterranean lands
The author has visited many countries in the Mediterranean region over a period of nearly 30 years, primarily during family holidays. In spite of recent and exciting advances in the state of bryological exploration in some Mediterranean countries (notably in Spain), other regions remain poorly known. There are still many territories where exploration has been conducted largely by visiting bryologists, and the literature is therefore fragmented and difficult to obtain. There is no modern comprehensive Flora for a Mediterranean country.
Much of the Mediterranean region is characterised by hot dry summers and cool moist winters. However, it is a large and varied region, with extensive mountain ranges. Rich bryophyte communities can be found at all altitudes and there is much for the visiting bryologist to see; even casual and opportunistic collecting can result in significant advances in our knowledge of these countries.
The author’s interest first began as a student of classical Latin and Greek, and many of his visits have taken in the classical antiquities. There is much of interest to be seen in and near such places. Equally, however, it is not difficult to gain access to the Mediterranean countryside to explore natural and semi-natural plant communities. A little research prior to a visit, both in the botanical and tourist literature, will often suggest areas of potential interest.
Examples of archaeological and other tourist sites where the author has found interesting bryophytes include: ·
- Pont du Gard, France. The River Gardon upstream from the famous Roman aqueduct passes through the Gorges du Gardon. Although at the northern limit of the Mediterranean region phytogeographically, the south-facing slopes of the Gorges provide a fine opportunity to see some characteristic thallose liverworts, e.g. Corsinia coriandrina (Spreng.) J. Lindb., Oxymitra incrassata (Brotero) Sérgio & Sim-Sim, Mannia androgyna (L.) A. Evans, and several Riccia spp., including R. michelii Raddi and R. ciliata Hoffm. s.l.
- Pozzuoli, Italy. The Bay of Naples is a fascinating region, full of cultural, historical and geological interest. Visitors go to see Vesuvius and the Roman town of Pompeii. But there are less frequented places to be seen. On the northern side of the Bay are some classic sites of Roman mythology. The town of Pozzuoli has a fine amphitheatre with a beautifully preserved substructure, and nearby a curious volcanic crater known as La Solfatara. Here is one of the few places on the European mainland where it is possible to see the moss Trematodon longicollis Michaux, which in Europe is very much associated with the volcanic parts of southern Italy (there is a single site in Crete).
- Segesta, Sicily. The large island of Sicily has several well-preserved Greek temples. During a visit in spring 1999, the author found an exceptionally fine population of Funariella curviseta (Schwaegr.) Sérgio at the beautifully situated temple of Segesta in the west of the island.
- Tiryns, Greece. The Mycenean civilisation which flourished in the second millennium BC left a notable architectural legacy, of which the best known and most visited example is the citadel of Mycenae. There is another citadel, Tiryns, not far away on the outskirts of the town of Argos, which like Mycenae was protected by remarkable so-called Cyclopean walls, built from massive blocks of red and grey limestone in the 13th century BC. During a visit in 1995 the author noticed a small thallose liverwort growing on compacted earth in a crevice on one of these walls. This proved to be Athalamia spathysii (J. Lindb.) S. Hatt. Müller (1951-58) in his classic European Flora gives a locality at Mycenae, a few kilometres distant. A. spathysii is not normally reported from man-made habitats, even those that are over 3000 years old!
- Festos (Phaestos), Crete. The Minoan civilisation in Crete is also one of great antiquity. A number of Minoan palaces from the second millennium BC have been excavated. It was at one of these, the palace of Festos, where the author made his first significant collection of Mediterranean mosses. These included a distinctive bud-like plant, with broadly revolute leaf margins. It was Tortula fiorii (Venturi) G. Roth, now generally treated as T. revolvens (Schimp.) G. Roth var. obtusata Reimers, which at the time was a new record for Crete.
- Episkopi, Cyprus. The remains of the Greek and subsequently Roman town of Kourion (Curium) are situated near the sea cliffs of the south-facing coast of Cyprus near Episkopi. The soft limestone of these cliffs supports a particularly interesting xerophytic flora, which includes Grimmia pitardii Corb., Aschisma carniolicum (F. Weber & D. Mohr) Lindb. and Gigaspermum mouretii Corb.
Sooner or later the bryologist in Mediterranean lands is likely to encounter distributional and taxonomic problems. While recent advances have solved some of these problems, others need further research. ·
- Gigaspermum mouretii is an example of a species with a fragmented distribution showing a strong disjunction between the eastern and western Mediterranean. It was described in 1912 from Morocco, but it was not until some 15 years ago that its known distribution was extended to southern Spain and subsequently Mallorca and the Canary Islands. G. mouretii has also been found in Israel, and the new locality in Cyprus reinforces the east-west disjunction.
- The genus Anacolia is an example which shows how our knowledge of distribution patterns may be complicated by taxonomic issues. Until recently the Mediterranean collections of this genus were presumed to belong to A. webbii (Mont.) Schimp., although 30 years ago Townsend (1965) noted that the Cypriot plants had much in common with A. menziesii (Turner) Paris. As a result of recent discoveries in Spain (García-Zamora et al., 1998) it is now known that both of these species occur in the Mediterranean. A. menziesii emerges as another east-west disjunct, although its distribution remains to be clarified in detail. It seems that A. webbii is a western Mediterranean species which extends eastwards to a single site in Sicily.
- Grimmia nutans Bruch also has a rare and fragmented distribution. It was described from western Turkey and remained neglected for many years until it was found in Greece, when it was first thought to be an undescribed species, G. meteorae C.C. Townsend (Townsend, 1989). There have been only two further records, from Tenerife and Cyprus. It remains unclear whether its distribution is really so fragmented as it currently appears. It seems likely that it may yet be found in Italy and/or Spain.
- Athalamia hyalina (Sommerf.) S. Hatt. is not an obvious choice of a Mediterranean bryophyte. It is in many ways a characteristic Arctic-Alpine species, widespread in Scandinavia and the Alps. But it also turns up as a rarity in sub-montane Mediterranean localities. It has been known on Crete for many years and it occurs in the south of mainland Greece, where the author collected it in two places in 1995, one of them at an altitude only slightly in excess of 1000 m, in a fairly benign Mediterranean environment. The common factor between these southern and northern stations appears to be a seasonally arid climate, to which A. hyalina is presumably well adapted.
- Anyone collecting species of Syntrichia (Tortula) in the mountains of the Mediterranean (Cyprus, for example) is likely to encounter specimens with a remarkable form of leaf ornamentation. On both surfaces of the cells the papillae are raised on mammillose extensions of the cell lumen – such that they are sometimes described as columnar. The significance of this character was discussed by Bizot (1954, 1956). The problem, taxonomically, is that the character occurs in a series of parallel forms with relationships to a number of different species in the genus. There is a ruralis form (S. papillosissima (Copp.) Loeske), a princeps form (Tortula echinata Schiffn.), and a virescens form (Tortula bizotii Lazarenko). Interestingly, there is also a corresponding form of Tortula muralis Hedw., T. israelis Bizot & Bilewsky. There is clear link with ecology and climate: most of these taxa occur in arid montane regions. But should they be regarded as species in their own right? Traditional techniques alone may not be adequate to solve the problem. Current treatments tend to rank them as subspecies or varieties. However, T. israelis is a particularly interesting case, as it occurs at low altitudes and its ecology overlaps with that of the widespread T. muralis.
- When it was found in Sussex new to Britain some years ago (Crundwell & Nyholm, 1972), Tortula freibergii Dixon & Loeske had all the appearance of being a very distinct species of its genus. Further finds have shown it to be very variable in its essential characters: the leaf cells may be smooth or papillose; the nerve may cease below the apex or may be percurrent or slightly excurrent; the marginal leaf cells are usually elongate, especially in the inner few rows, but sometimes indistinctly so. Its distribution is also difficult to explain. It occurs in widely separated localities in western Europe, but appears inexplicably rare. Collections made by the author during a recent visit to Sicily provide some evidence that T. freibergii may be an extreme form of T. solmsii (Schimp.) Limpr. occurring in relatively humid locations. Its identity therefore merits further investigation.
- Orthotrichum acuminatum H. Philib. shows how distinct taxa can remain poorly understood for lack of adequate collecting. It was described by Philibert (1881) from material collected in France and Italy, but in spite of its distinctive peristome remained poorly known for many years. In 1990 it was reported from new localities in Spain, and Spanish bryologists soon established that it was widespread in the Iberian peninsula. Recently it has also been reported from the Canary Islands. In 1995 the author found a small amount of it among material collected in southern Greece, and in 1998 found it several times in the Troodos mountains in Cyprus. This year he collected it again in Sicily. O. acuminatum is now seen to be a widespread and probably rather common Mediterranean species. It is remarkable, in view of its distinctiveness, that it could have been neglected for so long. There are surely other similarly neglected taxa in the Mediterranean literature awaiting rehabilitation.
- One such taxon is Cynodontium meridionale Herzog, which the author has had reason to investigate. Material of Cynodontium was collected in 1995 on the Methana peninsula in south-east Greece, at a site known locally as the Crater of Hephaestus. It is a lava field with massive blocks of tufa which retains a more-or-less natural vegetation in the deep hollows and crevices. Several of the bryophytes which occur there are unusual in the fairly severe Mediterranean climate in this part of Greece. Investigation of the Cynodontium led to the name C. meridionale, a species described by Herzog (1910) from Sardinia, and to collections made by the author during the BBS meeting in Portugal in 1989. Provisional conclusions are that C. meridionale is a distinct species occurring in Portugal and Sardinia. The Greek plant is similar and may belong to the same species, but it differs in a number of minor characters.
Bizot M. 1954. Remarques sur Tortula papillosissima (Copp.) Broth. Revue Bryologique et Lichénologique, nouvelle série 23: 268-270.
Bizot M. 1956. Nouvelles remarques sur Tortula papillosissima (Copp.) Broth. Revue Bryologique et Lichénologique, nouvelle série 25: 268-271.
Crundwell AC, Nyholm E. 1972. Tortula freibergii Dix. & Loeske in Sussex, new to the British Isles. Journal of Bryology 7: 161-164.
García-Zamora P, Ros RM, Cano MJ, Guerra J. 1998. Anacolia menziesii (Bartramiaceae, Musci) a new species to the European Bryophyte Flora. The Bryologist 101: 588-593.
Herzog T. 1910. Kritische und neue Arten der europäischen Laubmoosflora. Allgemeine Botanische Zeitschrift für Systematik, Floristik, Pflanzengeographie 16: 81-85.
Müller K. 1951-1958. Die Lebermoose Europas. 3rd edition. Band VI of Dr L. Rabenhorst’s Kryptogamen-Flora von Deutschland, Osterreich und der Schweiz.
Philibert H. 1881. Orthotrichum acuminatum. Species nova. Revue Bryologique 8: 28-31.
Townsend CC. 1965. Bryophytes from Cyprus. Revue Bryologique et Lichénologique, nouvelle série 33: 484-493.
Townsend CC. 1989. Grimmia (Musci): a variety new to The Lebanon and a new species from Greece. In: Tan K (ed.), The Davies & Hedge Festschrift, pp. 45-52. Edinburgh: Edinburgh University Press.
Dr Angela E. Newton (Natural History Museum, London): Bryophytes in amber from the Dominican Republic
The Paleobotany Department at the National Museum of Natural History (Smithsonian Institute) in Washington DC has a large collection of amber from the Dominican Republic. Many of these pieces of amber contain bryophytes, some with two or more species and several individuals. In 1995 I worked with collections from La Toca and Palo Alto mines, preparing them for microscopic examination and, as far as possible, identifying the taxa represented.
Amber is formed when the resin from certain trees undergoes fossilisation. The resin in this case comes from Hymenea protera Poinar (Leguminosae), which has close relatives still extant in the Caribbean. During the first stage of fossilisation the resin becomes polymerised and brittle, but remains soluble in alcohol. In this state the resin is known as copal, and is frequently dug up in large quantities to be used in varnishes or as incense. After several million years of exposure to heat, high pressure, and also seawater, the copal becomes transformed into amber. The age of the Dominican amber is uncertain, and may be anything from 20 to 40 million years old. Some of the amber deposits are overlain by Miocene reefs, so must pre-date these, giving a minimum age of 20-25 million years. Examination of associated fossils in the substrate gives an age of 30-45 million years for the La Toca mine, and 23-30 million years for the Palo Alto mine. However, the pieces may be older than this, as they show evidence of reworking, and so must have been redeposited some time after fossilisation. Nuclear magnetic resonance dating of the amber gives similar ages (30-40 million years for La Toca, 20-30 million years for Palo Alto), but these dates are relative to dates based on the fossil stratigraphy (Poinar, 1992).
Bryophyte specimens preserved in amber consist of little more than impressions and there is very little tissue present. Since amber is not soluble, and is too brittle to cut, preparation of amber for study usually involves grinding and polishing to provide thin sections and smooth surfaces. The resin when fresh is a viscous liquid, which will drip and flow across the substrate, usually either bark or soil. As a consequence the amber is full of flow lines, curved surfaces, bubbles, and various kinds of debris. All these artefacts cause tension and stresses in the amber, and exposure to shocks and vibration can cause sudden fracturing and fragmentation. The flow lines and curved surfaces also cause light diffraction that can prevent clear resolution of details.
The bryophytes themselves differ in the visibility and clarity of features. For example, in Lejeuneaceae many details of taxonomic importance may be visible. The plants grow in a single plane, and if exposed on both ventral and dorsal surfaces it may be possible to see features such as underleaves, lobules, rhizoids, stem epidermal cells, leaf shape and margins, cell shape, trigones and papillae, ocelli distribution, gemmae, and branching patterns. However, if the plants are attached to bark all the ventral details are obscured, and if the plants are curved or twisted it can be impossible to see anything clearly. Most moss specimens are much more difficult to work with, due to the tufted and three-dimensional growth form, imbricate leaf bases and curving leaves. Important details for identification, such as presence, distribution and shape of alar cells, are usually obscured by the overlapping leaves. Even the presence or absence of a costa can be impossible to verify unless it is very robust and extends beyond mid-leaf. Many mosses in amber appear to be desiccated, and therefore the leaves are usually in-rolled or collapsed, further obscuring details of the leaf margin and cell shapes. However, despite the impossibility of extracting and dissecting the bryophytes, it can be possible to find or make stem and leaf sections. In brittle-leaved species of Octoblepharum and Leucobryum there may be exposed sections within the amber. It is also possible, with care, to grind the amber in such a way as to cut through the bryophyte material and provide sections. These can then be stabilised by the use of certain resin-based glues.
Several of the taxa occur in other collections of Dominican amber (Frahm, 1993). For example, one of the most abundant mosses is a branching and weakly complanate member of the Neckeraceae, possibly Neckera (Frahm, 1993). In the Smithsonian material examined there appeared to be a weak, mid-length costa in some leaves, but this was extremely difficult to confirm due to leaf curvature and refraction in the amber. However, the presence of a costa would indicate that the plant belongs to Porotrichum, a common neotropical genus with several species extant in the Dominican Republic. Several species of Leucobryum have been found. In several of the specimens the cell layers can be seen in leaf sections resulting from natural breakage and from cross sections resulting from grinding. These show a pattern of cell distribution consistent with that seen in Leucobryum crispum. The leaf shape and posture also match this species.
Many of the species are very close to extant species, despite being 20 to 45 million years old. However, these are really very recent fossils, compared with the evolutionary history of the bryophyte lineages, which may cover 400 million years or more (Kenrick & Crane, 1997). These fossil assemblages, which include a wide range of taxa from many different plants and animals, provide insight into the past ecology of the Caribbean.
Frahm J-P. 1993. Mosses in Dominican amber. Journal of the Hattori Botanical Laboratory 74: 249-260.
Kenrick P, Crane PR. 1997. The origin and early diversification of the land plants. Washington DC: Smithsonian Institution Press.
Poinar GO. 1992. Life in amber. Stanford: Stanford University Press.
Nick Hodgetts (Joint Nature Conservation Committee, Peterborough) & Dr Chris Preston (Institute of Terrestrial Ecology, Monks Wood): Developments in biological recording
Chris Preston briefly reviewed the recent recording activities of the BBS, which culminated in the Atlas of the Bryophytes of Britain and Ireland and a database of 770,000 records held at the Biological Records Centre (BRC). This database is currently being updated with records submitted since the completion of the Atlas. It has been used in a number of research projects, including the Society’s own epiphyte survey, studies of hot-spots and complementary areas in different taxonomic groups, the identification of biogeographical zones based on environmental factors and species’ distributions, and the classification of bryophyte species into floristic elements.
Since the completion of the Atlas there have been major changes in biological recording. The current BSBI ‘Atlas 2000’ project illustrates how the ability of recorders to send data on disk has transformed the number of records which can be processed. The National Biodiversity Network (NBN) is a partnership which provides a framework for future recording activities. One aim of the NBN is to provide internet access to distributional data, including that held by BRC. It is hoped that, with the agreement of the BBS, the bryophyte data can be used as a pilot dataset in the development of this access.
In the years since the completion of the Atlas there has, inevitably, been a period of recuperation for bryophyte recorders. It may now be appropriate to review the Society’s recording activities, with a view to developing projects which would help existing members develop their field and identification skills and recruit new members. A number of possibilities were suggested.
Nick Hodgetts then explained how recording by BBS members could contribute to the conservation of threatened species through a scheme similar to the Threatened Plant Database Project (TPDP) that is currently under way as a co-operative venture between the statutory conservation agencies, the BSBI and Plantlife. Records of threatened species need to contain a higher level of information than records of species which are not threatened and, if a dataset of records of threatened species is to be useful for conservation purposes, it needs to be a ‘live’ database, not just an archive. The idea behind the TPDP is to co-ordinate BSBI membership to provide data on threatened species and, in return, to provide the membership with data as required. It was envisaged that it would be relatively straightforward to set up something similar with the BBS, given the existing network of vice-county recorders.
An important principle behind such a project is to devolve responsibility for data inputting and validation to those who actually know the plants – the BBS membership, in the case of bryophytes. This fits in well with the NBN, which is envisaged as a network of communicating databases rather than an unwieldy monolith. It was then explained how the information from such a database could be used effectively for conservation through Biodiversity Action Plans.
A further JNCC project just starting is the Species Status Project. This seeks to establish a more rational basis for assigning threat status (i.e. the IUCN threat categories of Endangered, Vulnerable, etc.) to species. As with the database project, the rationale is to devolve responsibility as much as possible to the experts, with an expert group for bryophytes (for example) being established to produce a draft list of species statuses, this being disseminated for consultation, and a ‘final’ list being published on a website. The list will be updated over an agreed timescale. The expert group will also have a role in ensuring that the latest bryophyte checklist is the standard used in NBN software such as Recorder 2000.
To summarise, bryological recording is in a transitional period, with increasing numbers of recorders becoming au fait with computers, and technology just beginning to do the things we want it to do. The future of bryophyte recording is still entirely in the hands of the BBS, but potential partnerships with other organisations, and initiatives such as the TPDP and the NBN, can potentially make our recording more useful and our records more usable. Atlases will always be useful, and increasingly easy to produce, but will be only one possible product; others include using bryophyte data in wider environmental studies and in analysing hotspots, biogeographical zones, etc. The BBS now has an opportunity to increase its influence and use its expertise more effectively by full involvement in these initiatives.
J.G. Duckett, A.M. Schmid (Queen Mary and Westfield College, London), R. Ligrone (University of Caserta, Italy) & K.S. Renzaglia (University of Southern Illinois, USA): Conducting tissues in bryophytes: cornerstones in land plant phylogeny
Some 35 years ago, when one of us (JGD) was young, enthusiastic and impressionable, he asked a wise bryologist for his views on evolutionary relationships between bryophytes and tracheophytes. The answer: bryophytes don’t work in the same way as vascular plants, and the deeper you investigate the greater are the differences. This is very much the current situation concerning conducting tissues; the more one studies their structure, development and function, the more differences one finds. Critical to reconstructing land plant phylogeny is the establishment of homologies, or lack of these, between the conducting elements of the various lineages.
The substantial literature on the structure of bryophyte conducting elements is reviewed in Hebant (1977). However, as with many things bryological, from purely structural data speculative functional and phyletic inferences have tended to become engrained in the literature without any developmental or experimental functional foundation. Establishment of homology requires structural, developmental and functional congruence (Ligrone, Renzaglia & Duckett, 2000).
Internal conducting tissues in bryophytes are restricted to the gametophyte generation in liverworts, are unknown in hornworts, but may occur in both generations in mosses. The key character of water-conducting cells (WCCs) is that they lack cytoplasmic contents and are dead at maturity (Raven, 1993). In liverworts these occur in the Calobryales and Pallaviciniaceae. The peg rhizoid-containing grooves on the stalks of the carpocephala of Marchantiales are an ‘internalised’ external water-conducting system. The WCCs in Calobryales are similar in shape to ordinary parenchyma cells and are perforated by plasmodesmata-derived pits, features shared with Takakia in the mosses. Those in the metzgerialean genera Hymenophyton, Pallavicinia and Symphyogyna are highly elongate with thickened pitted walls. These perforate WCCs most likely evolved independently in Calobryales, Metzgeriales and Takakia. In contrast, moss WCCs (hydroids) are very highly elongate cells with imperforate walls. Their differentiation includes obliteration of plasmodesmata and modification of the original transverse walls. Because of their loosely fibrillar appearance, in transmission electron micrographs, it has been generally assumed that the maturation of these walls involves enzymatic removal of non-cellulosic carbohydrates, though direct evidence for such ‘hydrolysis’ has never been produced. Our current studies have revealed that these walls contain a proteinaceous moiety that renders hydroids highly resistant to cavitation. Hydroids should now be regarded as a specialized WCC unique to mosses and related to poikilohydry. Homology with tracheids is highly implausible.
The food-conducting leptoids of polytrichaceous mosses, and the less specialised conducting parenchyma cells in the leafy stems and setae of other mosses, including Sphagnum and Takakia, have a highly distinctive cytology comprising cytoplasmic polarisation, axial arrays of endoplasmic microtubules associated with various organelles (including mitochondria and pleomorphic vacuoles) and numerous, highly differentiated plasmodesmata in their end walls (Ligrone & Duckett, 1994, 1998). Similar organisation, indicative of long-distance transport of nutrients, also occurs in moss rhizoids and caulonemata, in the internal parenchyma of metzgerialean and marchantialian thalli, and in the leafy shoots and underground axes of Calobryales (Ligrone et al., 2000). Although studies with radioactive tracers indicate that long-distance solute transport in bryophyte conducting cells is via mass-flow, the suite of cytological differences between these and sieve elements in tracheophytes almost certainly rules out homology.
Hebant C. 1977. The conducting tissues of bryophytes. Lehre: J. Cramer.
Ligrone R, Duckett JG. 1994. Cytoplasmic polarity and endoplasmic microtubules associated with the nucleus and organelles are ubiquitous features of food-conducting cells in bryoid mosses. New Phytologist 127: 601-614.
Ligrone R, Duckett JG. 1998. The leafy stems of Sphagnum (Bryophyta) contain highly differentiated polarized cells with axial arrays of microtubules. New Phytologist 140: 467-579.
Ligrone R, Duckett JG, Renzaglia KS. 2000. Proceedings of the Royal Society B (in press).
Dr Elizabeth Smith (University of Northumbria At Newcastle): The role of the photosynthetic carbon concentrating mechanisms in bryophytes
Four hundred and fifty million years ago many of the earliest plants possessed a ‘carbon concentrating mechanism’ (CCM) which increased the efficiency of photosynthesis, particularly in the aquatic environment. However, during the development of terrestrial vegetation the CCM was lost, although biochemical mechanisms which perform a similar function to the CCM (C4 photosynthesis and Crassulacean Acid Metabolism) evolved approximately 50 million years ago.
The Anthocerotae are of interest because they represent terrestrial organisms in which the carbon concentrating mechanism has persisted, at least within some genera. The activity of the carbon concentrating mechanism is correlated with the presence of a pyrenoid in the chloroplast, a region where the CO2-fixing enzyme Rubisco is located. Studies of members of the genus Anthoceros, which possesses a pyrenoid and a carbon concentrating mechanism, and the genus Megaceros, which does not possess a pyrenoid, are providing valuable data enabling us to elucidate the mode of action of the CCM.
Future research at the University of Northumbria will focus on gathering physiological data from this interesting group. We hope to elucidate the mechanism of the CCM in the Anthocerotae, and to carry out comparative studies of this strategy and the CCMs operating in a number of other non-vascular plants. The results of these investigations will enable us to address the question: why did land plants give up the advantage of a CCM only to develop a biochemical equivalent some 2-3000 million years later?
Smith EC, Griffiths H. 1996. The occurrence of the chloroplast pyrenoid is correlated with the activity of a CO2 concentrating mechanism and carbon isotope discrimination in lichens and bryophytes. Planta 198: 6-16.
Smith EC, Griffiths H. 1997. A pyrenoid-based carbon concentrating mechanism is present in terrestrial bryophytes of the class Anthocerotae. Planta 200: 203-212.
Smith EC, Griffiths H. 2000. The role of Carbonic Anhydrase in photosynthesis and the activity of the carbon concentrating mechanism in bryophytes. New Phytologist (in press).
Dr Jonathan Sleath (Kingstone, Herefordshire): Some observations on the bryophytes of the Marsyandi Valley, central Nepal
In July 1998 I had the opportunity to join a group from the Alpine Garden Society on a trek up the Marsyandi valley, in Central Nepal. The trek started from Dumre (450 m), about 75 miles to the west of Kathmandu, and followed the Marsyandi river northwards, behind the Annapurna massif to Thorong Phedi. From here we climbed to the Thorong La pass (5400 m) and retraced our steps back to Dumre. This was not a formal scientific expedition, but I was able to make some bryological observations, take photographs, and perform a little opportunistic collecting.
The track from Dumre to Besi-sahar (820 m) is not passable by vehicles during the monsoon season, which was when we were travelling. This subtropical area has very little natural vegetation, and is intensively cultivated for rice. The bryophyte flora was rather poor, with xerophytic thallose liverworts, such as Plagiochasma appendiculatum, on roadside banks, and Marchantia sp. forming extensive patches along the edges of the paddy fields. The epiphytic Octoblepharum albidum was present on some of the larger trees. Above Besi-sahar the valley begins to become narrower, and the cultivation more patchy. There are more areas of waste ground and disturbed woodland, although the epiphyte growth is poor (presumably due to the very seasonal rainfall) and the richest bryophyte communities are associated with wet rock faces. Mosses found here included Aulacopilum abbreviatum, Gollania schensiana, Racopilum orthocarpum and Scopelophila ligulata.
The path rises steeply before entering the village of Tal (1700 m), which is built on the shore of a lake formed by the Marsyandi when its outflow was blocked by a landslide. The thallose liverwort Exormotheca tubifera is abundant here on the sandy lakeside margins, together with Rhodobryum ontariense. The valley above Tal becomes narrower and more humid, but although there were plenty of waterfalls at this time of year, they had little bryophyte growth. On the moist rock faces there were large patches of Meteorium buchananii, together with Porella sp. and Asterella wallichiana. Fissidens grandifrons was found growing on an ox bone partly submerged in a flush. From Dharapani (1900 m) to Bagarchap (2100 m) there is more cultivation again, and above this point the path enters temperate woodland.
This is the richest area bryologically of the whole valley. The woodland is mainly broadleaved, with some Pinus wallichiana at higher altitudes. The epiphyte growth is relatively rich and includes Anomodon minor ssp. integerrimus, Leucodon secundus and Macromitrium hymenostomum. On the woodland floor were the mosses Plagiomnium cuspidatum, Rhytidium rugosum and Myurella sibirica, together with liverworts such as Jungermannia sp., Plagiochila sp., Chiloscyphus fragilis and the abundantly gemmiferous Lophocolea minor on rotting wood. This area is very unstable, and we had to pick our way carefully across several landslides, where Timmiella anomala was common. In some of the more open areas, Grimmia longirostris was present on the rocks, and thallose liverworts such as Asterella mussurensis and Mannia sp. grew beside the track. Beyond Bhratang (2800 m) the path veers up and away from the river, through some Pinus woodland, and into the lower Manang valley.
This upper part of the Marsyandi valley is much drier, being subject to a rain shadow effect from the Annapurna range. The landscape is more open, rather sub-alpine in appearance, and quite heavily grazed. Both the environment and the people show strong affinities with Tibet. Beyond Pisang (3200 m) there are patches of Betula utilis woodland with a good growth of Thuidium sp. and other pleurocarps. Although dry, some meadows receive moisture from flushes fed by seepage of glacial meltwater. Barbula pseudo-ehrenbergii is found here, along with familiar plants such as Palustriella commutata, Cratoneuron filicinum, Bryum sp. and Philonotis sp.
Above Manang (3500 m) the ground is very dry, most of the precipitation falling as snow in winter. The scrub is dominated by Rosa sericea and Juniperus. What few bryophytes there were seemed to be mainly restricted to deep rock crevices or the occasional flush. Once past Letdar (4000 m) there is more moisture under the dwarf shrubby Juniperus, Rhododendron and Berberis which permits the growth of Didymodon asperifolius, Syntrichia norvegica and Plagiopus oederianus. Many of the large boulders have circinate patches of Macrocoma sp. At higher altitudes, the ground becomes more barren, and the increasing number of unstable screes and landslides permits only limited bryophyte growth.
At Thorong Phedi (4500 m), the track leaves the Marsyandi, and ascends steeply to the pass at Thorong La. This is a silent and desolate arid wilderness of shattered rock and glaciers. Where the scree becomes stabilised there is a fascinating higher plant flora although the number of bryophytes is relatively few and includes Hypnum plumaeforme and Mnium thomsonii.
I have been very much indebted to David Long and Cliff Townsend for their assistance in the determination of the majority of the material collected. I have also had helpful advice from Howard Matcham, Brian O’Shea, Henk Greven, Dries Touw and Philip Sollman.
Field excursion to Chee Dale and Deep Dale, 12 September 1999
A field excursion was held on the Sunday of the AGM weekend to the limestone dales near Buxton in Derbyshire. The principal venue was Chee Dale, a reserve of the Derbyshire Wildlife Trust which has recently been extended by the purchase of ground immediately to the west of the old Millers Dale railway station. The car park at the disused station was our starting point for the day. We were pleased to be welcomed by Steve Price, the reserve manager, who acted as our guide.
The morning was spent in old quarries on the south-facing slopes near the station. The ground was dry and stony, and this limited the diversity of the flora. Didymodon ferrugineus and Aloina aloides were among the species seen. Many epiphytic bryophytes remain scarce in Derbyshire, so a record of Radula complanata on a tree at the edge of the quarry was very pleasing.
After lunch, members proceeded to Chee Dale proper, a wooded limestone gorge with precipitous crags. It was sad to see the erosion caused by the increasing numbers of rock-climbers who visit the gorge. The relatively dry conditions on the rock walls after recent dry weather permitted some species to be detected more easily than usual. Among those noted on the limestone cliffs and boulders were Preissia quadrata, Apometzgeria pubescens, Leiocolea alpestris, Pedinophyllum interruptum, Porella cordaeana and Cololejeunea calcarea. The mosses included Gymnostomum calcareum, Seligeria acutifolia and Orthothecium intricatum. Fissidens crassipes was in the River Wye. Careful searching on one crag eventually revealed very small amounts of Seligeria trifaria at this recently discovered site. It is unfortunate that this crag lies outside the reserve and is suffering particularly badly from the activities of rock-climbers.
A feature of the epiphytic flora of this part of the Wye valley is the abundance of Sanionia uncinata on some of the trees, fruiting profusely. Pylaisia polyantha, which was seen on several trees, also attracted much interest.
Deep Dale, a narrow valley running south-west from Topley Pike Quarry, had been put forward as an alternative venue for the day. A small group led by Tony (AV) Smith made this their main objective, recording Distichium inclinatum and Leiocolea badensis in the lower part of the dale near the Quarry. Another group made a quick incursion late in the afternoon in search of Brachythecium appleyardiae, found here a few years ago. The population was refound without difficulty on dry stones at the base of a crag. Also seen during this brief visit were Breutelia chrysocoma, in small quantity at a known site, and Scapania aspera.
Our thanks are due to the Derbyshire Wildlife Trust for permission to visit Chee Dale, and especially to Steve Price for his commendable patience at our characteristically slow progress through the reserve.