The customary autumn weekend meeting was held at Leicester University on 27 and 28 October.
Thirty-six members and guests attended the paper-reading sessions on the Saturday. The five speakers were introduced by the President, Dr E. F. Warburg, and summaries of the papers are given below:
Mr J. H. Dickson: ‘Observations on Neohodgsonia mirabilis from Tristan da Cunha’.
A brief account was first given of the situation, flora and phytogeographical significance of this south Atlantic island. Neohodgsonia, a monotypic genus of the Marchantiales, resembles Marchantia in general morphology but has bifurcate carpogoniophores. The complex nomenclatural history of the genus was reviewed. It is known also from New Zealand and Gough Island and almost certainly will be discovered elsewhere in the southern hemisphere. On Tristan it is widely distributed. Several slides were shown of its habitat, ranging from sheltered ground between tussocks of Spartina arundinacea and Blechnum palmiforme to wet rock faces in gullies.
Dr C. H. Gimingham: ‘Some aspects of bryophyte ecology in heathlands’.
The growth forms of bryophytes were first discussed with particular reference to their resistance to desiccation. The distinction was made between the weft form (exemplified by Pleurozium schreberi and Hylocomium splendens) and the mat form (Hypnum cupressiforme). The superiority of the latter in conserving water was demonstrated. In heath communities the frequency of these forms is clearly related to the micro humidity of the various phases of the Calluna growth cycle.
An illustrated survey followed of the heath communities in north-west Europe. It was shown that the various associations dominated by particular ericaceous species had characteristic bryophyte synusiae the inter-relationships of which paralleled those of the vascular plants.
Dr E. F. Warburg: ‘Some remarks on the genus Weissia’.
Recent research on this genus has revealed the existence of several taxonomic as well as nomenclatural problems, which may necessitate the description of a new species closely related to W. controversa, and the revival of W. longifolia Mitt. A critical evaluation was made of the characters used to separate species within the subgenera Weissia and Astomum. The importance of the following characters was discussed: leaf margin, width of nerve, length of mucro, cell and spore size. It was shown that a correlation existed between these characters in both subgenera and that most of the species fell into one of two groups, exemplified by W. controversa and W. rutilans, which were, in general, ecologically distinct.
The status of W. mittenii was considered and it was suggested that, combining as it does characters of W. multicapsularis and W. rostellata, it may prove to be of hybrid origin. This is also indicated by the relatively high proportion of bad spores. It was suggested that hybridity might be important elsewhere in the genus. In conclusion the need for pure taxonomic research on British bryophytes was urged. The ensuing discussion centred chiefly on the possible role of hybridization in this genus and in Bryum.
Mr S. W. Greene: ‘The bryophyte flora of South Georgia’.
The position and topography of South Georgia, a sub-antarctic island lying south of the antarctic convergence were discussed, followed by a review of the history of its bryological exploration. The 1960-61 botanical expedition to the island greatly extended the areas previously surveyed. The difficulties involved in identifying antarctic bryophytes were discussed and the need for a re-evaluation of all the taxa described from south polar regions was emphasized.
The sparse vegetation of South Georgia was illustrated by colour slides and the part played by the bryophytes in each community was mentioned. A notable addition to the island’s flora was Sphagnum fimbriatum; it occurs in Rostkovia magellanica bogs, and in one locality was seen to have formed about 40 in. of its own peat.
Dr G. Halliday: ‘The bryophyte flora of East Greenland’.
The bryophyte flora is remarkably constant throughout the Arctic. This uniformity, which is not the result of taxonomic ignorance, is considerably greater than that of the vascular flora. Some recent lists from Alaska suggest that about 85% of the bryophytes are common to arctic Europe. Even more pronounced is the similarity of the east Greenland bryophyte flora to that of arctic Europe. About 160 species of mosses have been recorded from east Greenland and of these only five have a west arctic distribution. A few are restricted in Europe to the Arctic (e.g. Schistidium tenerum) but the majority are arctic-alpine, extending southwards to the mountains of central Europe (e.g. Mnium hymenophylloides). In several species the arctic and southern populations are sub-specifically distinct.
Colour slides were shown of some of the bryophytes and the range of habitats in the region between 72 and 73° N. The high-arctic climate is relatively dry and there are few habitats with a continuous supply of melt water throughout the summer. Peat formation is local and the two species of Sphagnum, S. girgensohnii and S. warnstorfianum, are both restricted to the outer coast.
A conversazione was held during the evening in the Botany Department, by kind permission of Prof. T. G. Tutin. The following exhibits were shown:
|Miss A. P. CONOLLY:||‘Some late-glacial puzzles’.|
|J. H. DICKSON:||‘The first illustration of polysety?’.|
|J. H. DICKSON:||‘Neohodgsonia’.|
|Dr G. HALLIDAY:||‘Some east Greenland bryophytes’.|
|A. J. E. SMITH:||‘The B.B.S. Map Distribution Scheme’.|
|Dr E. F. WARBURG:||‘Seligeria oelandica Jens. & Med.; new to the British Isles’.|
|Dr E. F. WARBURG:.||‘Some species of Weissia’.|
|Dr E. F. WARBURG and A. R. PERRY:||‘Platygyrium repens (Brid.) B., S. & G.; new to the British Isles’.|
The excursion on the Sunday was attended by about twenty-five members and guests. Despite frequent heavy showers, a most rewarding and enjoyable day’s bryologizing ensued in north-east Leicestershire, a region which has received little attention from bryologists.
The party first visited King Lud’s Entrenchments and walked for about a mile along The Drift, which runs over the limestone uplands and here forms the Leicestershire-Lincolnshire boundary. Weissia crispa var. aciculata was noted and also several Pottia spp. including P. intermedia.
The next stop was at Barkestone Wood, in the Vale of Belvoir, where Plagiothecium sylvaticum s.s. and Bryum klinggraeffii were found. The most interesting finds, however, were made on the exposed shores of Knipton Reservoir. Of particular interest was the discovery by Mrs Paton and A. J. E. Smith of Ephemerum cohaerens*, known previously only from W. Sussex, Hertfordshire and S.E. Galway. Riccia crystallina was fairly frequent and associated with it were R. glauca and Physcomitrella patens.
[* = New v.c. record]
On the return journey to Leicester, a brief survey of the limestone walls in Branston resulted in Dr Gimingham finding Barbula convoluta var. commutata*.
Thanks are due to Mr S.W. Greene, who once again acted as programme Secretary, and to the Belvoir Estate for permission to visit Barkestone Wood and Knipton Reservoir.