A week-end meeting was held on 28 and 29 October in the Botany School, Cambridge, by kind permission of Prof. H, Godwin.
The programme on Saturday, 28th, consisted of paper-reading and a conversazione. The President, Miss E. M. Lobley, could not be present and so the task of introducing the four speakers fell to Dr E. F. Warburg.
Summaries of the papers follow:
Dr E. Lodge: ‘The Genus Drepanocladus’.
Some of the problems in circumscribing the genus Drepanocladus were briefly considered and then an account was given of transplant experiments which have been carried out on British material of D. fluitans and D. exannulatus. These investigations have shown that the two species are each represented in Britain by two distinct genotypes. Experimental control of the environment, however, has indicated that the two genotypes of each species are extremely plastic. The taxonomic implications of these observations were then considered. The paper concluded with a description of the work of the Finnish bryologist, Tuomikoski, on the Fennoscandian races of D. exannulatus.
Mr D. Briggs: ‘Experimental Studies in the Genus Dicranum’.
Four species of Dicranum had been studied, D. fuscescens, D. majus, D. scoparium and D. bonjeanii and evidence was presented, from morphological studies, which showed that these were, in fact, good species.
Intra-specific variation within the group was examined and the results of culture experiments were given which indicated that such characters as undulation of the leaf-tip and leaf stance could be modified by altering the external environment and were probably unreliable as key-characters, at species or varietal level. Varieties based on entireness of leaves were also difficult to apply as the variation in serration appeared to be continuous.
The results of cytological investigation into Dicranum populations were also presented. Intra-specific variation in chromosome number was shown to occur in D. fuscescens, D. majus and D. scoparium and also variation in ‘small’ chromosomes. The chromosome variation did not appear to ‘follow’ the morphological variation. (Full details of these Dicranum studies will be presented elsewhere.)
Mr J. H. Dickson: ‘Some preliminary observations on the Quaternary Moss Flora of Britain’.
The kinds of fossil mosses found in British Quaternary deposits were indicated by means of slides.
Four deposits were explained in some detail. Two of these, referable to the late glacial period at Low Wray Bay, Windermere (Zone II) and Loch Droma, Wester Ross (Zone I) were dealt with in such a way as to show how fossil moss assemblages can help in reconstructing past environments.
The moss floras of the full-glacial deposits at Colney Heath, Herts, and Broome, Norfolk, were used to demonstrate distributional changes. Thus, Cratoneuron filicinum var. curvicaule, Oncophorus virens, Scorpidium turgescens and Timmia sp., found at Broome, were far outside their present British ranges during the full glacial period.
Dr J. H. Tallis: ‘Some observations on Sphagnum imbricatum’.
Measurements of leaves of Sphagnum austini Sull. ( S. imbricatum Hornsch. ex Russ.) and of the variety imbricatum Lindb., differing in their lax and compacted growth-forms respectively, show that the two taxa differ significantly in the length:breadth ratio (1·175 ± 0·078 and 1·547 ± 0·114 respectively). Transplant experiments indicate that the two are merely growth forms, controlled by the height of the water-table. Measurements of S. imbricatum leaves preserved in Sub-Atlantic peats from three areas show variation in the length:breadth ratio, suggesting that S. imbricatum may have adopted different growth forms during accelerated and retarded phases of peat formation. The principal theories concerning the behaviour of S. imbricatum in recent peats largely fail to take into account the detailed stratigraphy observable in some bog peats.
Many of the 30 members and guests present contributed to the lively discussion of the papers and Dr E. F. Warburg warmly thanked the speakers.
In the evening a conversazione took place and the following exhibits were presented:
|J. H. DICKSON, P. E. BROWN and P. J. HASTINGS:||‘ Meesia longiseta Hedw. in Britain’.|
|S. W. GREENE:||‘A Botanical Dryer suitable for Bryophytes’.|
|P. J. GRUBB:||‘Polysety in Polytrichum’.|
|R. E. LONGTON:||‘Polysety’.|
|Dr F. H. PERRING:||‘The preparation of Grid Square Distribution Maps’.|
|J. H. G. PETERKEN:||‘Colour Transparencies of Bryophytes’.|
|Dr C. D. PIGOTT:||‘Distribution Maps of Sphagnum imbricatum and Camptothecium nitens’.|
|Dr L. B. C. TROTTER:||‘Drawings showing the Histology of Mosses’.|
|Dr S. M. WALTERS:||‘W, E. Nicholson’s Diaries, and the Nicholson Herbarium’.|
|Dr H. L. K. WHITEHOUSE:||‘Rhizoid tubers in British mosses’.|
|Dr H. L. K. WHITEHOUSE
and Mrs M. P. WHITEHOUSE:
|‘A possible association between species of Riccia and the occurrence of Phascum cuspidatum Hedw. var. bivalens Springer’.|
|Mrs M. P. WHITEHOUSE:||‘Stereoscopic colour transparencies of Bryophytes and Bryologists’.|
On Sunday, 29th, about 25 members and guests set off by private transport under perfect weather conditions to see some of the rarer bryophytes of the Cambridge district. First, a stop was made at Quy Fen, where a very large patch of Tortula vahliana was seen on a north-east facing clay bank beneath elders and brambles. A stubble field at Horningsea yielded Ephemerum recurvifolium and Bryum klinggraeffii.
Next the party visited the ancient earthwork, the Devils Dyke, where it crosses the A. 45 (Cambridge to Newmarket), to see chalk grassland bryophytes, including Weissia sterilis and Tortella inclinata, Dr E. F. Warburg quickly found Tortella inflexa, a new vice-county record. This species has since proved to be common on chalk lumps on a 3 mile stretch of the Dyke, west of the original locality. It may well be that careful searching will show that the species is common over the greater part of the 10-mile-long Dyke, where there are suitable chalk lumps.
At Lakenheath Warren, in Suffolk, v.c. 26, Eurhynchium pulchellum var. praecox and abundant Rhytidium rugosum were seen. In the adjoining Forestry Commission plantation at Wangford Warren, Dicranum rugosum, originally found by Mr M. Macfarlane, and Rhytidiadelphus loreus, found by Dr H. L. K. Whitehouse, were shown to the party. Much to everyone’s astonishment, Mr S. W. Greene discovered a large clump of Ptilium crista-castrensis, a new record for southern England. Shortly afterwards, two further clumps were found. Another new county record was made with the discovery of Odontoschisma denudatum on a rotten pine stump.
Close searching of a fairly small area of the plantation has yielded over 20 localities of Ptilium, a species totally unexpected in this part of Britain. It seems likely that the species has been introduced, and with this in mind, Dr H. L. K. Whitehouse is trying to find the origin of the trees (Scots and Corsican Pine) from the Forestry Commission. Dicranum rugosum has also proved to be common at Wangford.
The discovery of Ptilium brought a fine day’s bryologizing to a fitting end.
Thanks are due to the local secretary, Dr H. L. K. Whitehouse, whose careful organization was of great assistance to the meeting which was a success in every way, to the Botany School for providing refreshments, to Dr E. F. Warburg for taking the chair, to Dr J. H. Tallis for speaking at short notice in place of Dr C. H. Gimingham, and to Mr S. W. Greene who has not only acted as programme secretary for three of the week-end meetings so far held, but was responsible for their initiation.
James H. Dickson