The Tenth International Botanical Congress Bryological Excursion was held at Bangor, North Wales, from 21 to 28 July and was attended by 28 botanists. Bangor proved to be an ideal centre both in being situated in an area of varied topography and geology with a mild oceanic climate and in having available the laboratories and accommodation of the University College of North Wales. It was the aim of the organizers of the excursion to show something of the diverse bryophyte flora of North Wales and to give some indication of the structure and composition of the communities of various types of habitat.
The localities and types of habitat that we visited were as follows:
Wednesday, 22 July. The rocky gorges of the Afon Dulyn and Afon Ddu.
Along the west side of the Vale of Conway are a series of wooded gorges with fast-flowing streams descending from the mountains. Two of these streams were visited: the Afon Dulyn, near Tal-y-bont, flowing through a deep humid gorge over rocks which are base-rich in parts; and the Afon Ddu, near Dolgarrog, which flows over acid rocks and has a less humid atmosphere. The relative paucity of species by the Afon Ddu is in marked contrast with the abundance of species by the Afon Dulyn where the high humidity and the presence of basic rock produce a rich flora.
Thursday, 23 July. Coed Crafnant, Cwm Bychan and the Roman Steps.
Coed Crafnant is a sessile oakwood (Quercus petraea) on the steeply sloping east bank of the Afon Artro near Llanbedr. The rocks on which the wood is situated are mainly very hard grits and shales, the floor of the wood is terraced, the horizontal parts often being very wet and supporting bog species.
To the east of Coed Crafnant is Cwm Bychan, a valley from which leads the Roman Steps, a medieval pack-way, to a pass known as Bwlch Tyddiad. In the lower part of Cwm Bychan is a small humid wood and the upper part consists of heath and bog. The Roman Steps and the path through Bwlch Tyddiad run beside cliffs and boulder scree and provide easy access to species characteristic of rocks and rock-ledges of the submontane parts of North Wales.
Friday, 24 July. Cwm Dyli and Glaslyn, Snowdon.
Glaslyn is a lake situated near the top of a glaciated corrie, Cwm Dyli, on the east side of Snowdon. The geology of Snowdon is complex. The rocks are of varying acidity and basicity and provide conditions suited to a variety of species of bryophytes.
Saturday, 25 July. Rhaeadr Du and Cader Idris,
Rhaeadr Du consists of two waterfalls in a stream flowing through the Coed Ganllwyd National Nature Reserve. The Reserve is situated on the southern flank of the Harlech Dome of Cambrian rocks; it contains a dolerite sill which provides the base-rich habitat necessary for some of the plant species present. The stream runs through a gorge in a Quercus petraea wood and a striking feature is the extreme humidity resulting from the continual spray from the waterfalls.
The bryophytes from the north side of Cader Idris are mostly the same species that grow in the corries of Snowdon; the main interest of the part of the mountain that we visited is the comparison between the bryophytes of extremely acid rocks and of basic rocks in the vicinity of Llyn-y-Gafr where two different rock strata outcrop.
Sunday, 26 July. The Menai Straits and the Aber Valley.
The Menai Straits separate the island of Anglesey from the mainland of North Wales near Bangor. Much of the coastal rock is Carboniferous Limestone but some of the rocks are Ordovician and Pre-Cambrian and are acid.
Geologically the Aber Valley is of Ordovician rocks which are mainly acid. With high humidity and rainfall the valley supports the rich bryophyte flora characteristic of such areas in North Wales.
Monday, 27 July. Tywyn Aberffraw
The sand-dunes known as Tywyn Aberffraw, although relatively small in area when compared with other dune systems in Wales, have an extremely rich and interesting bryophyte flora. The dunes are calcareous, except in the oldest parts where they may be acid as a result of leaching. On the northern margin of Tywyn Aberffraw are several calcareous flushes by the Afon Ffraw.
Discussion of findings
It is clear that a considerable number of different types of habitat were visited, including acid and basic woodlands of varying humidity, submontane and montane localities and coastal sites. In the ensuing account bryophyte species are listed in the habitats in which they most commonly occurred. This does not mean, however, that they were entirely restricted to those habitats.
The notable feature of most of the woods (Coed Crafnant, Coed Ganllwyd, those by the Afon Dulyn, in Cwm Bychan and in the Aber Valley) was the high humidity with the consequent rich growth of mosses and liverworts on the ground, on rocks and on trees and the presence of many small species on rotting logs and epiphytic on other bryophytes.
The most important species of the ground flora were usually Atrichum undulatum, Brachythecium rutabulum, Dicranella heteromalla, Dicranodontium denudatum, Dicranum majus, D. scoparium, Eurhynchium praelongum, Fissidens bryoides, Hookeria lucens, Isopterygium elegans, Leucobryum glaucum, Mnium hornum, M. undulatum, Plagiothecium undulatum, Pleurozium schreberi, Rhytidiadelphus loreus, Thuidium delicatulum, T. tamariscinum, Calypogeia arguta, C. fissa, Lepidozia pinnata, L. reptans, Lophocolea cuspidata, Pellia epiphylla and Plagiochila asplenioides. In drier and less humid parts the ground flora was sparser and poorer in species and the only plants usually seen were Dicranum scoparium, Polytrichum formosum, Pleurozium schreberi, Plagiothecium undulatum, Thuidium tamariscinum and Lophocolea cuspidata. Where, however, the floor of a wood was waterlogged and the canopy open, as for example in Coed Crafnant, many wet-ground species were seen such as Acrocladium cuspidatum, Aulacomnium palustre, Brachythecium rivulare, Polytrichum commune, Sphagnum compactum, S. cuspidatum, S. imbricatum, S. palustre, S. papillosum, S. plumulosum, S. rubellum. S. subsecundum, Blepharostoma trichophylla, Cephalozia bicuspidata, Odontoschisma denudatum, O. sphagni, Ptilidium ciliare and Trichocolea tomentella. Most of the paths in the woods visited had a poor flora, being too well trodden, but Ditrichum lineare, characteristic of such a habitat, was found (new to Wales) on a path beside the stream in Coed Ganllwyd.
Several common species were seen to occur both on trees and rocks; such species were Dicranum scoparium, Hypnum cupressiforme, Isothecium myosuroides, Mnium hornum, Bazzania trilobata, Frullania dilatata and Plagiochila spinulosa. Species restricted mainly to rocks in and around the woods included Amphidium mougeotii, Bartramia pomiformis, Bryum capillare, Dicranoweisia cirrata, Dicranum scottianum, Grimmia hartmanii, Hedwigia ciliata, H. integrifolia, Ptychomitrium polyphyllum, Rhacomitrium spp., Diplophyllum albicans, Marsupella emarginata, Saccogyna viticulosa, Scapania gracilis and S. umbrosa. Where there were base-rich rocks several other species such as Barbula recurvirostris, Camptothecium sericeum, Encalypta streptocarpa, Fissidens cristatus, Grimmia apocarpa, Tortula intermedia and T. muralis were noted.
Species which are mainly corticolous and which thrive in North Wales where atmospheric pollution is low included Orthotrichum affine, O. lyellii, Ulota bruchii, U. crispa, Zygodon viridissimus and Lejeunea ulicina.
Some of the more interesting bryophytes were those occurring on rotting logs, wet peaty soil and creeping over other bryophytes. These included Tetraphis pellucida, Aphanolejeunea microscopica, Drepanolejeunea hamatifolia, Harpalejeunea ovata, Lejeunea cavifolia, L. lamacerina var. azorica, L. patens, L. ulicina, Lophozia longidens, L. ventricosa, Nowellia curvifolia, Riccardia palmata and Tritomaria exsecta.
Rocks in the wetter parts of Coed Crafnant and in and beside streams in such woods as Coed Ganllwyd and in Cwm Bychan provided habitats for many species, the most important ecologically of which were Blindia acuta, Brachythecium plumosum, Eurhynchium riparioides, Heterocladium heteropterum, Hygrohypnum eugyrium, Hyocomium flagellare, Thamnium alopecurum, Rhacomitrium aciculare, Trichostomum tenuirostre, Marsupella emarginata and Scapania undulata. Species that were less common, but of interest because of their mainly oceanic distribution in Britain. included Campylopus setifolius, Isothecium holtii, Sematophyllum demissum, Ulota hutchinsiae, Jubula hutchinsiae and Plagiochila tridenticulata.
In the montane and submontane regions the contrast between the floras of acid and basic rocks and between exposed and sheltered north-facing rock outcrops or cliffs was most noticeable; the basic rocks and north-facing cliffs having a greater number of species and the combination of the two producing an abundance of species met with in few other parts of Great Britain.
Exposed acid rocks had a poor flora, the main components of which were Hedwigia ciliata, Ptychomitrium polyphyllum, Rhacomitrium fasciculare and R. heterostichum (in its many forms) with Andreaea rothii, A. rupestris and Campylopus atrovirens on rocks receiving some flow of water. On the ground and banks and in crevices amongst the rocks were such plants as Dicranum scoparium, Oligotrichum hercynicum, Plagiothecium undulatum, Polytrichum aloides, Rhacomitrium lanuginosum, Diplophyllum albicans, Nardia scalaris and more rarely Diphyscium foliosum and Oedipodium griffithianum. Where the rocks were calcareous, as for example by Llyn-y-Gafr, the common rock species were Barbula recurvirostris, Grimmia apocarpa, Ctenidium molluscum and Tortella tortuosa. These species were frequently brightly coloured and the reds and yellows were in marked contrast with the dull greens and greys of the species on acid boulders.
Flushes in the mountains were marked by species such as Bryum pseudotriquetrum, Dicranella palustris, Philonotis fontana, Scapania undulata, Sphagnum spp. and Pellia epiphylla, again making a bright splash of colour. Where the flushes were basic more species were present and in addition to some of the above there were Acrocladium sarmentosum, Campylium stellatum, Cratoneuron commutatum var. falcatum, Drepanocladus revolvens and Scorpidium scorpioides.
The richest areas were the shaded cliffs above Glaslyn on Snowdon, above Lyn-y-Gafr on Cader Idris, beside the Roman Steps and above Bwlch Tyddiad. These cliffs, containing both acidic and basic rocks, provide a variety of habitats including dry rock faces, extensive areas of damp or wet rocks, rock ledges, and humid crevices in rocks and scree. Many of the species in the previous two paragraphs were frequent. Plants of rocks not subjected to a surface flow of water included Brachydontium trichodes, Grimmia atrata, G. conferta, G. funalis, G. ovalis, G. patens, G. stricta, G. subsquarrosa, G. torquata, Pterogonium gracile, Gymnomitrion concinnatum, G. obtusum, Lophozia alpestris and Porella laevigata. Species of damp or wet rock surfaces were Arctoa fulvella, Barbula ferruginascens, Bryum alpinum, Dicranum falcatum, Fissidens osmundoides, Gymnostomum aeruginosum, Rhacomitrium ellipticum, Anthelia julacea, Cephaloziella pearsonii, Cololejeunea calcarea, Marsupella alpina, M. emarginata, M. sphacelata, M. ustulata, Mylia taylori and Scapania undulata. Rock ledges and crevices had an abundance of species amongst which were Amphidium lapponicum, A. mougeotii, Anomobryum filiforme, Bartramia ithyphylla, Breutelia chrysocoma, Distichium capillaceum, Ditrichum flexicaule, Encalypta ciliata, E. vulgaris, Hookeria lucens, Hypnum callichroum, Isopterygium pulchellum, Plagiobryum zieri, Plagiopus oederi, Pohlia acuminata, P. cruda, P. ludwigii, P. polymorpha, Polytrichum alpinum, Rhabdoweisia crenulata, R. denticulata, Trichostomum brachydontium, Barbilophozia floerkii, Diplophyllum taxifolium, Marchantia polymorpha var. alpestris, Preissia quadrata, Reboulia hemisphaerica, Scapania aequiloba, S. curta and Tritomaria quinquedentata.
Whilst the above lists give some conception of the species present it gives no idea of the spectacle provided by the abundance and colour of plants such as Breutelia chrysocoma, Bazzania tricrenata, Herberta hutchinsiae and Mylia taylori. The collection of species such as is found on the cliffs above Llyn-y-Gafr is quite remarkable and caused considerable comment amongst the visiting bryologists.
The Carboniferous Limestone on the shore of the Menai Straits was the only limestone locality that we visited and here, especially in seepage areas, were a number of species not seen elsewhere. The most frequent species were Anomodon viticulosus, Barbula tophacea, Ctenidium molluscum, Eucladium verticillatum (forming tufa in several places), Neckera complanata, N. crispa, Pottia heimii, Rhynchostegiella tenella, Thamnium alopecurum, Trichostomum brachydontium, T. tenuirostre, Ulota phyllantha, Leiocolea badensis, L. turbinata, Lunularia cruciata, Radula complanata and Riccardia sinuata.
The last day at Tywyn Aberffraw was specially noteworthy because of the great interest of some of the species that grew there. The mobile dunes were bare of bryophytes or had occasional patches of Tortula ruraliformis, a species that was seen to be widespread throughout the dunes. The fixed dunes were little richer, there usually being Barbula spp., Brachythecium albicans, Camptothecium sericeum, Ctenidium molluscum, Hypnum cupressiforme var. tectorum and Frullania tamarisci.
The remarkable bryophyte flora is associated chiefly with the dune slacks and with the flushes by the Afon Ffraw. The flora of the slacks varies with the height of the water table. Species of the wetter parts of the dune slacks that were seen included Acrocladium cuspidatum, Bryum pallens, B. pseudotriquetrum, Campylium polygamum, C. stellatum, Dicranella varia, Mnium undulatum, Leiocolea badensis, L. turbinata, Pellia fabbroniana, Riccardia pinguis, Southbya nigrella (the only known Welsh locality), Moerckia flotoviana, Petalophyllum ralfsii, and Preissia quadrata. The last three species are characteristic of dune slacks in Wales. In the drier parts of the slacks and on sandy patches in dune pasture were Barbula fallax, B. unguiculata, Camptothecium lutescens, Campylium chrysophyllum, Climacium dendroides, Cratoneuron filicinum, Ditrichum flexicaule, Encalypta streptocarpa, Pleurochaete squarrosa, Rhodobryum roseum, Tortella inclinata, Tortula ruralis and Trichostomum crispulum. In and near the calcareous flushes and pools at the northern edge of Tywyn Aberffraw were Acrocladium cordifolium, Amblyodon dealbatus, Catoscopium nigritum, Cratoneuron commutatum var. falcatum, Drepanocladus sendtneri, Meesia uliginosa, Mnium seligeri, Philonotis calcarea and Marchantia polymorpha var. aquatica.
A notable feature of the dunes is the unusual admixture of southern Mediterranean species such as Pleurochaete squarrosa and Southbya nigrella and boreal species such as Amblyodon dealbatus, Catoscopium nigritum and Meesia uliginosa (which strangely enough are not known from the mountains of North Wales).
As there was no Bryological Section at the Edinburgh Botanical Congress the Bangor excursion provided the only opportunity for all the bryologists attending the Congress of meeting together. It was unfortunate that the weather during the period 21-28 July was not better. Whilst none of the excursions was rendered impossible by rain, low cloud and occasional showers prevented a full appreciation of the scenery of North Wales.
Some idea of the attraction of North Wales was provided at a reception given by the University College of North Wales on the first evening in an introductory talk by Prof. Richards illustrated by coloured slides after an address of welcome by the Dean of the Faculty of Science. The excursion was rounded off by an informal dinner followed by a ‘Welsh Entertainment’ on the final evening.
A. J. E. Smith
Appendix. Participants on the Bryological Excursion
Mr G. C. G. Argent, Bangor
Mr A. C. Crundwell, Glasgow
Miss E. Clausen, Copenhagen
Mr R. D. Fitzgerald, Hexham
Mrs J. W. Fitzgerald, Hexham
Dr M. Fulford, Cincinnati
Prof. H. Gams, Innsbruck
Mr S. G. Harrison, Cardiff
Dr M. J. Harvey, Halifax. Canada
Mr C. Jeffrey, New Maldon
Prof. A. Kalela, Helsinki
Mrs Kalela, Helsinki
Prof. M. Lange, Copenhagen
Mrs B. Lange, Copenhagen
Dr E. Lawton, Washington
Dr F. LeBlanc, Ottawa
Dr W. S. G. Maass, Halifax, Canada
Mrs E. Nyholm, Stockholm
Mrs J. A. Paton, Truro
Prof. G. Sayre, Massachusetts
Dr J. T. de Smidt, Utrecht
Dr W. C. Steere, New York
Mrs D. O. Steere, New York
Prof. G. S. Torrey, Connecticut
Mrs Torrey, Connecticut
Miss Torrey, Connecticut
Dr A. Touw, Leiden
Dr E. F. Warburg, Oxford
Dr W. S. Lacey, Bangor
Prof. P. W. Richards, Bangor
Dr A. J. E. Smith, Bangor.