The autumn weekend meeting was held on 28-29 October in the Department of Botany, Royal Holloway College, by kind permission of Professor K. Wilson. On the Saturday, papers were read under the chairmanship of the President, Mrs J. Appleyard. Summaries are given below.
Dr E. V. Watson: ‘Reflections on some difficult or controversial species in the genus Pohlia.’
Following a short introduction which dealt with fundamental questions relating to the determination of bryophyte material, an outline was given of the present position as regards several distinct ‘situations’ in Pohlia, where the relationships between the British species are imperfectly understood. The following were briefly discussed: (1) Relationship between Pohlia acuminata, P. polymorpha and P. elongata. (2) Pohlia nutans and its allies, with special reference to the dioecious species P. sphagnicola and P. marchica. Attention was drawn to some plants which had been collected by Dr E. F. Warburg on Berkshire commons and provisionally referred by him to P. marchica – not hitherto recognized as a British species. (3) Some relatively easily recognized species, P. cruda, P. crudoides (non-British) and P. ludwigii. (4) Gemmiferous Pohlia species, with special reference to the varied interpretations of the P. annotina – P. proligera boundary line. (5) P. pulchella and P. lutescens, the former recently recognized, the latter about to be published as British species. (6) The subgenus Mniobryum, with brief reference to the varieties calcarea and glacialis of P. wahlenbergii. Most of the remarks were of a tentative nature, pending more detailed work on the genus.
Dr P. J. Grubb: ‘Uptake and redistribution of mineral nutrients in Polytrichum formosum, latest facts and theories.’
Evidence was presented for the existence of a selective system of uptake for cations between the soil and the shoot. The experiments previously described as showing no evidence of this type (cf. Trans. Br. bryol. Soc. 1961, 4 , 184; 1965, 4 , 900.) were reconciled with the present evidence by assuming that some damage results in the rhizome system from washing out from soil and/or the use of too simple salt solutions. Evidence was also presented for the redistribution of potassium, nitrogen and phosphorus from old regions to new. Calculations have shown that this occurs too fast to be accounted for by diffusion alone. Movement within the symplasm is likely to be most important in most mosses; in Polytrichum and a few others the leptome may be important. The primary selective system of uptake from soil to shoot might work either via the symplasm of the shoot as a whole or via the rhizome cortex alone, followed by passive movement in the hydrome.
Dr A. Eddy: ‘Bryophytes of New Guinea’.
Dr E. Lodge: ‘Epiphyllous bryophyte communities of Jamaica’.
Various general features of the biology of epiphyllous bryophytes were briefly reviewed and the distribution of these organisms in Jamaica was considered in relation to its forest types. An examination of a large number of ‘host’ leaves has revealed that a rich flora of epiphyllous bryophytes, comparable with that reported for Guadeloupe and Martinique by Jovet-Ast, is to be found on the island. So far, fifty-seven epiphyllous species (mostly belonging to the Lejeuneaceae) have been identified, twenty-five of these representing additions to the known bryophyte flora of Jamaica. Individual leaves of ‘host’ plants may be treated as relevés for phytosociological analysis, the epiphylls occurring on each one being listed and their cover-abundance assessed, using the ten-point Domin scale. Preliminary attempts to synthesize these data have indicated that several associations of epiphyllae may be represented in Jamaica. Some of the more clearly defined of these were described and illustrated by colour transparencies.
Dr D. H. Lewis: ‘The distribution of sugar alcohols in bryophytes and its possible taxonomic significance.’
Following the discovery of an acyclic polyhydric alcohol (polyol) with the chromatographic mobility of volemitol in Lophocolea bidentata, a range of leafy liverworts was analysed. Compounds tentatively identified as mannitol, sorbitol and volemitol (alone or in combination) were found in many and none in others. The polyols co-existed with hexoses, sucrose and a series of soluble fructosans. In all cases where more than one species of a genus has been examined, the pattern of polyols was consistent, e.g. Scapania (mannitol); Marsupella, Gymnomitrion and Nardia (sorbitol); Lophocolea and Chiloscyphus (volemitol); Lepidozia (volemitoi with sedoheptulose); Plagiochila (volemitol with mannitol); Porella (none). In several families, e.g. Marsupellaceae, Scapaniaceae, and Bazzaniaceae, all genera examined were also homogeneous, whereas in others this was not so. Frequently in the latter case the limits of the families have been treated differently by various authorities. This difference of treatment for the genera Harpanthus, Saccogyna, Mylia, Anthelia and Odontoschisma by Arnell, Müller, Jones and Schuster was illustrated in relation to their polyol content and that of allied genera. It was suggested that the possession of a particular combination of polyols was a ‘good’ generic character and may be of value in delimiting taxa above this level (family or subfamily).
Dr J. H. Dickson: ‘Late Quaternary history of Meesia tristicha and Dicranum undulatum.’
The ecology and distribution of the two species were briefly described. Relict status is clearly shown by the present patterns supported by numerous sub fossils. Important periods in the decline of Meesia tristicha were the Late-glacial/Post-glacial transition, and the Boreal-Atlantic transition. The major fragmentation of D. undulatum took place in the last 2,500 years; anthropogenic destruction of the bog habitats was a principal factor.
After discussion and questions put to the speakers, the President thanked them and Dr Dickson for arranging the paper-reading programme. In the evening a conversazione was held in the Botany Department’s new laboratories where a large number of exhibits were on display:
|Mr K. J. ADAMS:||A mapping scheme for Essex bryophytes.|
|Miss S. BOYD ANDREWS:||Paintings of bryophytes.|
|Dr P. D. COKER:||Distribution of some ‘copper’ mosses in Britain. The distribution of epiphytic bryophyte communities in the British Isles. Some microclimatic measuring apparatus used in bryophyte ecology.|
|Dr J. H. DICKSON:||Stereoscan microscopy of bryophyte spores.|
|Mr M. V. FLETCHER:||Reading bryophytes.|
|Mr E. R. B. LITTLE:||Oil bodies of Riccardia.|
|Mr E. R. B. LITTLE:
and Mr J. G. DUCKETT:
|Mnium medium in Britain.|
|Mr S. T. LICENCE:||Hypnum lindbergii in Essex.|
|Mr K. LEWIS:||Exhibition of bulbiferous Pohlias.|
|Dr E. LODGE:||Epiphyllous bryophytes from Jamaica.|
|Mr A. J. PERRY and Mr M. V. CORLEY:||Name this bryophyte.|
|Miss A. L. D. SOUTHORN:||Bryophyte recolonization of burnt areas.|
|Mr W. J. SYRATT:||The effect of sulphur dioxide on bryophytes.|
|Mr P. J. WANSTALL:||Epiphyllietum.|
|Dr E. V. WATSON:||Some species of Pohlia.|
On the Sunday the field excursion was held. In the morning the party visited an area of calcareous fen and river bank at Greywell, N. Hants (v.-c. 12). A number of interesting plants was seen, in particular quite a large group of epiphytes, including Cryphaea heteromalla, now becoming more and more scarce in the S.E. of England. Plagiothecium latebricola was also seen. In the afternoon the party moved on to Hazeley Heath. On disturbed ground by the road, many small acrocarps were seen, including some fine Barbula hornschuchiana. A heavy downpour slowed down operations, but members went on to look at wet heath, valley bog and some fields. Cephalozia bicuspidata var. lammersiana* was discovered on the heath, Riccia sorocarpa* on soil in a field and Bryum pallens on gravelly waste ground.
[ * new v.-c. record ]
Dr E. Lodge must be thanked for organizing a very interesting and successful meeting.
E. R. B. Little