Taxonomic workshop 1982: Bradford University

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27 November 1982 - 28 November 1982

Workshop report

Fourteen members of the B.B.S. attended a two-day taxonomic workshop at the University of Bradford, 27-28 November, 1982. The first day was spent in the laboratory of the School of Environmental Science: the morning session was devoted to the genus Scapania and the afternoon session to small acrocarps of soil, under the direction of Mr. David Long and Mr. Tom Blockeel, respectively.

A short talk was given, which outlined the general features of Scapania, hints for field collection, drying, preparation of specimens for microscopic examination, and described some of the important characters used in distinguishing the British species, namely gemmae, perianths, leaf cuticle, size and shape of leaf lobes, structure of the keel, border development, leaf decurrence and oil-bodies. Herbarium specimens, prepared slides and important literature were provided for reference. Participants then studied specimens of a range of species and identified these using several recent keys.

Small acrocarps should be collected with copious soil in order not to lose any vegetative propagules. Specimens are best wrapped in paper and placed in a box or other container to prevent crushing. If they cannot be examined fresh, they should be dried as soon as possible to avoid fungal infection. The low-power binocular microscope is especially useful in sorting specimens and preparing them for examination under higher power. Whenever possible the opportunity should be taken to search for tubers, particularly in such genera as Bryum where they are of diagnostic value. This may be achieved by placing a stem or two, with soil attached, in a drop of water and cleaning away the soil and debris with a needle or brush, repeating the process one or more times in clean water. For final examination a single stem should be teased apart to minimise the risk of foreign tubers mistakenly being identified with the wrong stem. When present, the tubers are usually readily discernible under the binocular microscope at a magnification of x30 or less.

Archidium Contrary to statements in some floras, A. alternifolium is usually fertile. However the capsules may be concealed at ground level among the sterile innovations. These innovations are distinctive with widely-spaced leaves becoming shorter towards the tip of the stem.
Ditrichum D. cylindricum is a frequent species, but easily overlooked. The wiry, flexuose leaves have a distinctive facies, and the apical part of the subula is toothed all round. Tubers are constantly present.
Pleuridium The androecial shoots of P. subulatum are persistent, but the inflorescence of P. acuminatum may be difficult to prove in mature plants. It is therefore easier to identify plants before development of the capsules (still recognisable as Pleuridium by the long perichaetial leaves).
Dicranella D. schreberana, D. rufescens, D. varia and D. staphylina are separable on leaf characters (i.e. leaf orientation, denticulation and cell width), but tubers are useful confirmatory characters, especially in D. schreberana and D. staphylina, and they may enable very immature or poorly developed shoots to be named.
Barbula B. fallax and B. tophacea commonly occur on soil. Both have elongated cells overlying the nerve, although this character may not be well expressed in small or immature plants. B. tophacea often has tubers, similar to those of B. tomaculosa, but more variable and less conspicuous. B. tomaculosa may prove to be widespread: the tubers are plentiful and therefore conspicuous. Among other characters, B. fallax differs from it in having papillose cells, and B. tophacea in the broadly shaped apical half of the leaf. The cells overlying the nerve of B. tomaculosa do not differ markedly from the laminar cells, but may be shortly rectangular.
Pohlia P. lutescens is a frequent species, and should not be mistaken for P. carnea. It has narrower leaf cells and a much more opaque leaf of a yellow green colour. Flagelliferous shoots are frequently produced. The tubers are diagnostic but may be difficult to detect because of their shape and colour.
Bryum The ‘erythrocarpum‘ group cannot usually be named without tubers. Once detected, the tubers are distinctive and allow ready recognition of most of the species. B. rubens is sometimes difficult to separate from B. microerythrocarpum: the former typically has tubers with protuberant cells clustered at the base of the stem and leaves with wide cells and a distinct border, the latter smooth tubers not clustered at the base of the stem and leaves with narrower cells (<15µm) and the border poorly developed. B. bicolor which has lost its bulbils may be mistaken for B. ‘erythrocarpum‘ however, it is usually distinct in its more concave leaves, and the fallen bulbils can often be found in the soil.

On the second day a field excursion was held to Broadhead Clough near Mytholmroyd, recently acquired as a Nature reserve by the Yorkshire Naturalists’ Trust. The clough is an open bowl-shaped valley running up to the Calderdale moorland near Halifax. Though scenically attractive, with woodland of oak, birch and holly, it has only the impoverished bryophyte flora characteristic of the South Pennine areas which have long endured severe atmospheric pollution. The elimination of epiphytic and rupestral species has allowed limited colonisation of trees and rocks by tolerant opportunists such as Orthodontium lineare and Campylopus paradoxus. Wet habitats have a slightly more diverse flora. Hyocomium armoricum and Nardia compressa were recorded by streams, and Tetradontium brownianum on wet grit rock. Three species of Sphagnum, S. recurvum var. mucronatum, S. fimbriatum and S. palustre, were on wet ground on the woodland floor.

The approach to the Reserve, through pasture-land, gave the opportunity to observe small acrocarps on banks by the track. Some of the species discussed on the previous day were present, though not all could be proved in situ. They included Pleuridium acuminatum (a young state with mature inflorescences), Pseudephemerum nitidum, Weissia rutilans, Pohlia lutescens, Bryum rubens and B. sauteri. Scapania scandica was also present. Some of these species, including the Pohlia, were seen on the banks of the Cragg Brook along with Ditrichum cylindricum, fruiting Dicranella schreberana and Bryum gemmiferum.

We are most grateful to our two speakers, the local secretary (Dr. Mark Seaward), and the University of Bradford for such a useful and enjoyable meeting.

Tom Blockeel


Bradford University