THE LATE DEVENSIAN VEGETATIONAL HISTORY OF THE WHITLAW MOSSES, SOUTHEAST SCOTLAND

Transcription

1 Phytol. (1982) 91, THE LATE DEVENSIAN VEGETATIONAL HISTORY OF THE WHITLAW MOSSES, SOUTHEAST SCOTLAND BY J. A. WEBB AND P. D. MOORE Department of Plant Sciences, King's College, 68 Half Moon Lane, London, SE24 9JF, U.K. {Accepted 23 October 1981) SUMMARY Late Devensian Late-glacial deposits are described from the Whitlaw Mosses, near Melrose, Roxburghshire (now Borders). Pollen diagrams and macrofossil lists are given for the bottom sediments of Beanrig Moss and Blackpool Moss, two small fens lying in hollows in the undulating boulder clay of Tweeddale. The succession of taxa through the sediments indicates interstadial conditions followed by stadial conditions. Critical determinations of certain microfossil and macrofossil indicator taxa, permits the identification of certain plant communities. These are as follows: Communities identified from within the stadial are; (1) bare-ground communities of open, wind-exposed areas with Artemisia cf. norvegica and Papaver spp. of the section scapiflora as the main indicator types; (2) bare-ground communities in sheltered areas of long snow-lie with such species as Salix herbacea, Polytrichum norvegicum and P. alpinum. The main communities identified in the interstadial are as follows: (1) scrub with shunddint Juniperus and sparse tree birches (e.g. B. pubescens); (2) base-rich, well-drained short turf with abundant Helianthemum; (3) damp, tall-herb meadows in which Rumex acetosa is important; (4) dwarf-shrub heath with Dryas octopetala and Betula nana; (5) open-ground communities with Artemisia spp. and Hippophae. Communities identified from both the stadial and interstadial are: (1) short-turf calcareous flushes or springs with Selaginella and various mosses; (2) fens and marshy lake margins with, e.g. Homalothecium nitens. Several taxa have not hitherto been found in the Late Devensian of the British Isles, amongst which are Artemisia cf. campestris, A. sect, dracunculus, A. cf. maritima s.l., Gypsophila repens/fastigiata, Hedysarum cf. hedysaroides, Minuartia rubella, Rhacomitrium cf. canescens and Vaccinium vitis-idaea.the identification of the pollen grains and macrofossils is discussed and comments are made on the biogeographical and ecological implications of the records, especially of those species which are now no longer part of the British flora. INTRODUCTION Inferences regarding contemporaneous vegetation derived from fossil assemblages generally lack precision when resolution into plant communities {sensu lato) is attempted. Success in this area depends in part upon the degree of taxonomic precision achieved in the fossil identifications and in the combined use of microand macrofossil data to gain information, together with the nature of the depositional site. In this study, cores from two adjacent small basins, comprising sediments of Late Devensian Late-glacial age are analyzed and compared in order that detailed conclusions concerning the nature and spatial heterogeneity of past vegetation can be achieved X/82/ $03.00/ The New Phytologist

2 342 J. A. WEBB AND P. D. MOORE ^^'NETHER WHITLAW // FARM ^'\ AvirrS^^-.S^= ^-.. Fig. 1. Sketch map of Southern Scotland and Northern England (above), showing the location of the Whitlaw Mosses (black square). The lower map (larger scale) shows the detailed arrangement of the Mosses.

3 Vegetational history of the Whitlaw Mosses 343 The series of deposits known collectively as the Whitlaw Mosses lies on the old Selkirkshire-Roxburghshire border, at the northeastern extremity of the Southern Uplands, and approximately 5 km outside Selkirk, near the A 699 to St. Boswells (see Fig. 1). To the northwest and north lie respectively the Moorfoot and the Lammermuir Hills, and 30 km to the south and southeast, the Cheviots. The River Tweed curves around the sites some 5 km to the north and continues eastwards out of the Southern Uplands. The countryside surrounding the sites is gently undulating, mostly pastoral farmland with numerous small hollows containing lakes or ponds in various stages of terrestrialization. The Whitlaw Mosses occupy four such hollows between 245 m and 275 m above sea level in which the basins have been filled completely with peat. The parent rocks of the area are the Silurian Birkhill Shales and Gala group of the Llandovery Series; these lower Palaeozoic rocks being tightly folded and almost vertically disposed, the effect of erosion on alternating bands of hard and soft rock giving a micro-relief of closely spaced ridges and hollows - the so called' corrugated hills' (Ragg, 1960). The parent rocks are covered by till or stony drift and solifluction deposits, the till being a rather fine-textured, brownish grey matrix with lumps of greywacke and shale. The orientation of landforms, such as drumlins and crag and tail features in lower Tweeddale, suggests that the main directions of iceflow over the area during the Devensian were northeast and east, roughly following the valley of the Tweed from a dispersal centre in the middle of the Southern Uplands. This centre is the Broad Law, Hart Fell and White Coomb area where the rivers Tweed, Annan and Clyde now rise. Broad Law is approximately 32 km from the Whitlaw Mosses. It is reported by Sissons (1974) that this small centre carried glaciers during the Loch Lomond readvance (stadial of the Late Devensian Late-glacial, equivalent to Godwin's Zone III, 1975). Beanrig Moss (National Grid Reference 36/517293) and Blackpool Moss (36/517289) are only two of the five sites which make up the Whitlaw Mosses, all within a radius of 1-5 km (Eig. 1). They are all eutrophic valley or basin fens, fed by base-rich ground water and showing a range of rich fen communities, ranging from open bryophyte-rich areas through tall herb associations to closed willow carr (Daniels, 1972). Blackpool Moss is the larger, at its longest axis approximately 300 m long, whilst Beanrig Moss is no more than 200 m long. The two sites are separated by 150 m of pasture land, through which a connecting drainage ditch has been cut. STRATIGRAPHY The stratigraphy of the sites was investigated by means of a series of borings, 25 m apart along the transects shown in Eigure 2. Borings were taken using a Russian peat sampler (Jowsey, 1966) and were described in the field. The stratigraphic profiles are given in Eigures 3 and 4. The profile from Blackpool Moss (Eig. 4) is presented relative to the water table, which was at or near the peat surface. Dense carr vegetation rendered more precise levelling impossible. The basal deposits in both profiles are divided into four stratigraphic units (SUs) which are used as the basis of subdividing macrofossil records. Their relationship to detailed stratigraphy is given in the following sediment descriptions.

4 344 J. A. WEBB AND P. D. MOORE (a) Limit of carr 50 m Fig. 2. (a) Plan of Beanrig Moss Showing surface contours in feet above an arbitrary datum point and position of stratigrapbical transects (adapted from Daniels, 1972). (b) Sketch map (not to scale) of Blackpool Moss to show the position of stratigraphical transects and isolated borings.. Two profiles will be described in greater detail. Core 4C from Beanrig Moss has the following sediment stratigraphy: m m m m Slightly humified Sphagnum peat with Molinia roots and leaves, Salix roots, modern Phragmites rhizomes, Vaccinium oxycoccus leaf More humified fen peat with Molinia roots, Equisetum roots. Ranunculus (subgenus Batrachium) achenes. Moss remains between 0-70 and 0-90 m More compact and fibrous peat (orange-brown but turning black on exposure to air) with Phragmites and Equisetum remains, Menyanthes seeds, Carex vesicaria nutlets and utricles. Some clay detectable (SU4) A grey-brown, finely fibrous, clayey, coarse detritus mud. Potamogeton leaf fragments and fruitstone. Equisetum roots. Band of silt at 1-40 m and more silt towards 1-55 m (SU4)

5 Vegetational history of the Whitlaw Mosses 345 3C 4C 5C 6C 7C OT -hiatus L I t L _ L 1,7 SU4 Clay <7'-4 L L L-t L L L L L clay' L L L L L L L L L L L SU2 Q \ Dicot. leaves ff- I Myriophyllum shoots 3-- L L L L T ' L L L L L L H t II L L L L L L L L L L SUI ^ I Eriophorum angustifolium roots A I Wood ^ Sphagnum 7tr\ Mosses other than Sphagnum Hill Swamp or fen peat I/X^ Coarse detritus mud luul Marl [UL] Clay l»i Shells..[ Silt and sand 4-- \*\P\ Angulor rock fragments Metres Fig. 3. The stratigraphy of Beanrig Moss along transect C. l'55-l 70 m '' m Blue-grey clay with roots penetrating from above (SU3) Fine, greenish-grey muddy clay which contains small fragments of Acrocladium giganteum (SU3) m Grey clay with included plant material (mostly bryophytes) (SU3) '' m Grey clay with small angular rock fragments (SU3)

6 346 J. A. WEBB AND P. D. MOORE EAST A (bank) B D Fine detritus mud Laminated mud Metres Fig. 4. The stratigraphy of Blackpool Moss along a roughly east-west transect. Symbols as in Fig. 3. 2O m Khaki-coloured, clayey and silty, coarse detritus mud with Phragmites fragments and Equisetum roots (penetrating from above) (SU2) m Khaki-coloured clayey and marly coarse detritus mud. Much plant material. Flakes of CaCOg and shell fragments obvious (SU2) m Soft, grey and pink banded clay (SU2) m Marl band with yellowish nodules of CaCOg (SU 1)

7 Vegetational history of the Whitlaw Mosses WEST H J (Bank) Potamogeton fruitstones Q. a> Q Fig. 4 continued. 225 Metres M Soft grey clay with slightly organic (clay-mud) bands at 3-12, 3-45 and 3-70 m (SUl) '-ore H from Blackpool Moss has the following stratigraphy: U'u0~0-65 m Dark brown rooty swamp peat of variable wetness and with abundant Phragmites. U'Oi-0-75 m y/ m Band of unhumified Acrocladium cuspidatum and other mosses Light brown or orange brown Phragmites peat varying from very wet and sloppy to very compact. Texture suggestive of coarse detritus mud. Wood fragments. Bryophytes, fruit stones of Potamogeton.

8 348 J. A. WEBB AND P. D. MOORE m Very fibrous swamp peat, made up of vascular strands of Equisetum with a little Phragmites m Coarse detritus mud with wood, Equisetum, Phragmites, Betula bark, Salix leaves, Potamogeton fruit stones 4-(X)-4-90 m Fine, dark brown detritus mud, often banded with black layers. Betula pubescens twigs and leaves. Salix leaves, Potamogeton fruit stones, Valvata piscinalis shells (SU4) m Dark green-black detritus mud with Valvata and soft, marly nodules. Pisidium species present (SU4) m Dark, grey-green detritus mud with shells (SU4) m Light, grey-green, clayey detritus mud (SU3) m Pink-brown, banded with grey slimy clay. Fragments of mosses (SU3) m Light grey-green detritus mud with some clay (SU2) m Dark, grey clayey detritus mud (SU2) m Pink and grey banded slimy clay. Stones at 6-48 m (SUl) 7-00-m No penetration Lake sediments of Late Devensian Late-glacial character occur very near to the present peat surface at Beanrig Moss, but lie underneath approximately 6 m of lake muds at Blackpool Moss. From the apparent hiatus within the peat at Beanrig Moss, it was concluded that the sequence was truncated, an amount of peat formed during the post-glacial having been removed. Blackpool Moss, on the other hand, appeared to have undisturbed sediments, since it had been a small lake until fairly recent times. METHODS Cores collected using a Russian sampler were stored in plastic containers at 2 C. Only the sediments of Late Devensian Late-glacial character were investigated by pollen and macrofossil analysis. At Beanrig Moss the same core (4C) was used for pollen and macrofossil analysis but at Blackpool Moss core H was used for pollen analysis and the core I from 25 m away for macrofossil analysis. Pollen extraction was conducted using standard techniques (see Moore and Webb, 1978); Frdtman (1960) acetolysis was employed, together with HCl treatment and boiling in lif. Four slides were made for each level and counting was carried out with a Zeiss binocular phase-contrast microscope. Routine counting was carried out under X 400 magnification, critical identification under x 1000 magnification oil immersion and phase contrast. The fossil pollen sum included the pollen grains and spores of all dry land plants and those wetland types not considered to be local. Grains of Cyperaceae, spores of Sphagnum and of the Pteridophyta were included in the sum, whilst grains of Potamogeton, Typha spp., Myriophyllum spp., Nymphaea, Menyanthes, spores of Equisetum and colonies of algae were excluded from the sum. At Beanrig Moss the total fossil pollen sum was allowed to vary from level to level, ranging between extremes of 836 and 383 grains, with most counts falling between 550 and 750 grains. This variation was occasioned by the fact that an attempt was made to estimate pollen concentration by use of the method described in Bonny (1972) whereby exotic marker pollen is added to the sediment and a count is made of fossil plus exotic grains to a total of At Blackpool Moss the total count of fossil pollen grains per level was kept constant at 650 and the total of fossil plus exotic was allowed to vary between levels. In addition, at Blackpool Moss, those portions ofthe four slides which had not been covered during the count were

9 Vegetational history of the Whitlaw Mosses 349 scanned, and any pollen types new to the level were noted. These 'outside the count' records were indicated on the diagram by a different symbol from ' inside the count' records. In the pollen diagrams, the counts of the individual taxa inside the sum are presented as percentages of the total fossil pollen, along with the 95 % confidence limits of these percentages (calculated for each taxon in the manner described by Mosimann, 1965). No confidence limits have been calculated for pollen and spore types which are outside the sum or present in very small quantities (a cross or a letter on the diagram). The values of types outside the sum are displayed on the diagrams as a percentage of total land pollen plus the particular taxon. Sediment samples for macrofossil analysis were taken at selected intervals and were dispersed in water (with the addition of detergent in the case of clay samples and 10% HCl in the case of calcareous ones). The suspensions were then sieved and all the remains retained by a 100 mesh to the inch sieve were sorted in a Petri dish with the aid of a low power binocular microscope. If the samples contained obvious mollusc shells, these were removed before the rest of the sample was treated with HCl. Contiguous 5 cm deep sections of the core, each with a volume of approximately 30 cm^, were the basis for the qualitative data (Fig. 8). Added to the diagram from Beanrig Moss are the results from another core taken at point 4C between the depths of l'5o and 2*50 m. This core (which was originally collected as a duplicate) was examined in order to test the hypothesis that analysis of 30 cm^ samples was sufficient to show the general pattern of occurrence of taxa. At Beanrig Moss, estimation of the changes in abundance of the commoner taxa was made by recording the numbers of each macrofossil taxon sieved from the 1 cm^ of sediment used for the preparation of the pollen slides (see Fig. 7). Identifications were made by comparison of the fossils with type material and by reference to the works of Katz, Katz and Kipiani (1965), Bertsch (1941) and Beijerinck (1947) for the macrofossils; Faegri and Iversen (1947), Erdtman, Berglund and Praglowski (1961), Erdtman, Praglowski and Nilsson (1963) and Moore and Webb (1978) for the pollen grains and spores. The nomenclature of the pollen taxa identified is in accordance with that in Moore and Webb (1978) except in the cases discussed in the Appendix. The Appendix contains full descriptions of the most important pollen and macrofossil identifications. British plant names are after Clapham, Tutin and Warburg (1962) and Smith (1978). Non-British plant names are after Tutin et al. ( ). THE POLLEN DIAGRAMS Pollen diagrams for the two sites are given in Figures 5 and 6. They have been zoned according to the fiuctuations in what are here considered to be the more important taxa, i.e. Betula (tree), Betula nana-type, Juniperus, Salix, Filipendula, Thalictrum, Empetrum, Oxyria-type, Cruiciferae, Helianthemum, Cerastium-type and Artemisia. The zone boundaries have been located at positions on the diagrams where marked changes occur in the curves for one or more of the above taxa (taking into account the 95 % confidence limits of the percentages). The sporadic occurrences of grains of Quercus, Alnus, Picea, Corylus and Ulmus shown on the diagrams are not considered in the account which follows. It is assumed their presence can be explained by long distance transport, redeposition or contamination.

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14 354 J- A. WEBB AND P. D. MOORE Beanrig Moss {Eigure 5) The following is a brief description of the pollen and spore characteristics of the zones into which the diagram is divided. Zone BRM-a High values for Salix (up to 20 %) and Rumex acetosella (up to 15 %). Betula (tree) and Betula nana-type behave erratically; Juniperus values very low (2 to 3 %). A wide variety of open-ground herb and shrub taxa found at very low percentages. Of especial interest are Artemisia type-b, Artemisia type-f, Papaver, c.f. Medicago falcata, Lonicera, Gentianella cf. amarella. Subzone flg- Declining values for Rumex acetosa-\- acetosella, Salix and Myriophyllum alterniflorum. Peak values (27%) for Betula (tree) and Rubiaceae (5%). Betula nana type behaves very erratically. Zone BRM-b High values ior Juniperus and Helianthemum, low values for Salix (3 to 4%). Range of open ground taxa as BRM-a with a few additions - those of especial interest being Artemisia type-a, Gypsophila fastigiata/repens, Saxifraga cernua/ rivularis, Hedysarum cf hedysaroides, cf. Erangula alnus, Gentiana cf. verna and Scabiosa. Hippophae consistently found in traces. Subzone b^. The highest values for Helianthemum (9-3%). Subzone b^. The highest values ior Juniperus (23 to 28%). Zone BRM-c. High values for Artemisia (total) (up to 15%), Oxyria-typQ (15 to 19%), Cerastium-type (2 to 6 %), Cruciferae (4 to 8 %), Saxifraga oppositifolia (1 to 5 %), Thalictrum (5 to 10%), Pinus quantities noticeable. Very low values ior Jfuniperus (1 to 2 %) and Betula (tree) (2 %). Range of rarer taxa similar to BRM-a and BRM-h. At two levels within this zone pollen was too sparse for a count to be made. Nevertheless, it was felt that the following subzones could be recognized. Subzone c^. Transition period with rising Artemisia type-a, and Artemisia indetermined; falling Gramineae from peak of 34 %. Subzone c^. Highest values (for diagram) for Artemisia type-a (15 to 16%), and lowest values (for diagram) for Gramineae (10 to 15%). Subzone c^. Transition period with declining Artemisia type-a and Oxyriatype. Rising Gramineae, Rumex acetosa + acetosella. Ranunculus type and Myriophyllum alterniflorum. Zone BRM-d Covers another transitional period, with sequential short-lived peaks in Rumex acetosa-{ acetosella (15%), Ranunculus type (6%), Rubiaceae (2%), and Myriophyllum alterniflorum (63 %). Steadily increasing Betula (tree) and Eilipendula. Gramineae rises to a peak (43 %) and then falls. Jfuniperus still low (2 %). Traces of Oxyria-type, Artemisia type-a, Cruciferae, Cerastium-type, Saxifraga oppositifolia, B. nana type. Few grains of Typha latifolia and Urtica-type. Zone BRM-e jfuniperus rises quickly to a peak of 38%. Peak in Eilipendula (10%). Betula (tree) rises steadily to peak of 20%. Gramineae declining from BRM-d peak.

15 Vegetational history of the Whitlaw Mosses 355 Empetrum has a small early peak (11%) but declines for most of this zone. Declining Myriophyllum alterniflorum and M. spicatum; Typha angustifolia-type, Cosmarium and Euastrum reach peaks. Equisetum rising. Blackpool Moss (Figure 6) For all the taxa found here, the histograms show fluctuations of smaller amplitude than for the same taxa at Beanrig Moss. Consequently (bearing in mind the confidence limits of the proportions), the diagram has been much more difficult to zone than that of Beanrig Moss. A brief description of the pollen and spore characteristics of the zones follows. Zone BPM-a Defined on relatively high values for Filipendula and low values for Oxyria type, Cruciferae and Artemisia (total), jfuniperus is present at just under 10% as are Betula (tree) and B. nana-type. Salix is present in low amounts, Gramineae and Cyperaceae prominent. Empetrum, Thalictrum and R. acetosa present at under 10%. Helianthemum present continually in trace amounts. A wide variety of herbaceous and shrub taxa are found in trace amounts. Especially of interest are Artemisia types - A, B, C, D and E, Arenaria type s.s., Silene acaulis/nutans, cf. Lychnis viscaria/alpina, Gypsophila fastigiata/repens, cf. Astragalus alpinus, cf. Medicago arabica/lupulina, cf. Swertia perennis and Astragalus danicus-type. Subzone BPM-a^. Juniperus and Gramineae values steady or declining slightly {Juniperus 17 to 11 %, Gramineae 29 to 19%). Subzone BPM-a^. Steadily rising jfuniperus (12 to 23%) and Gramineae. Juniperus reaches a peak of 23 % at end of zone. Zone BPM-b Transition period defined by steadily decreasing Jfuniperus (down to 10 %) and increasing Cruciferae (trace up to 2%). Helianthemum at highest value (5%) for diagram. Rumex acetosa, Helianthemum, Betula (tree) and Empetrum all show declines at the end of this zone. The range of rarer taxa of herbs and shrubs remains similar to that of BPM-a. Of especial interest in this zone are the single-grain records of Symphytum, cf. Echium and Ononis-type. Zone BPM'C This is the zone of high Artemisia type-a (up to 6%) and Cruciferae (1 to 7%) along with low Filipendulai^\ %). Subzone BPM-c^. Transition period defined by a temporary peak in Cruciferae. Artemisia type-a increasing steadily throughout and jfuniperus, Betula (tree) and Empetrum declining steadily throughout. Saxifraga oppositifoua appears as at least 1 % of total pollen. Rarer taxa seen for the first time at this site are Hedysarum cf. hedysaroides. Subzone BPM-C2. Highest values for Artemisia type-a (5-5 %). Lowest values (within the zone) for Juniperus (5*3%) and Helianthemum (2%). High Betula nana-type (17%) and Thalictrum (9%). Artemisia types - B and C present. Cerastium up to 3 %. Of especial interest amongst the rarer taxa seen are Silene cf. acaulis/nutans and Saxifraga cernua/rivularis. Subzone BPM-c^. Artemisia type-a lower and Cruciferae, Helianthemum and x acetosa higher than in Cg. The beginning of this period is marked by a sudden increase in the values ior Jfuniperus (3 % to 16%). It remains at this higher

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17 Vegetational history of the Whitlaw Mosses 357 -K u _c o CJ ~ *- so : 4-

18 358 J. A. WEBB AND P. D. MOORE CD CL 03 Q- CQ Q. CQ CL CQ r^ n n J = J e J I n n -4- M n n n n 4-4- n n n n 4-4- n n n 4-4- n n 4-4 n n n n 4 4 r, 4-4,-, r, J I J ^ Op III fii Q- II II -a 0) C 0 u vo bb 4-: n - n n n n n _ fl fl 6» fl- g -»- fl o en 9 fr & fl fl fl ft fl # fl fl fi- -B- fl- :.. fr^ fr 9 & & fl O 0. s ft fl- iiflfl a 6 fr ^» «- -

19 Vegetational history of the Whitlaw Mosses 359 level throughout the subzone and the end of the period is marked by another sharp increase in this taxon (rising to 45 %) accompanied by rises in Betula (tree) of 3 to 10% and Filipendula of 1 to 7 %. At the same point sharp declines are shown by Gramineae (29 to 14%). Cyperaceae (14 to 5%), Thalictrum (6% to 1%), Oxyria-type (4% to 1%), Rumex acetosa (4% to 1%), and Artemisia type-a (2 to < 1 %). THE MACROFOSSIL DIAGRAMS Beanrig Moss As the diagrams have not been divided into 'macrofossil zones', the main features are described below with reference to depth, stratigraphical units (SUs) and pollen zones, where relevant. Quantitative diagram {Fig. 7). The most interesting distributions are shown by the oosporangia of Chara, Nitella and Tolypella. Chara shows its greatest abundance in the detritus mud SU4 (pollen zones BRM-d and BRM-e). It is absent in the clay of SU 3 (pollen zone BRM-c) and sporadic in the silty detritus mud (upper part of SU2, pollen zones BRM-a, ag, b^, bg). Oosporangia of Chara occur at only one level in the lower, more marly and clayey detritus mud (lower part of SU2). Nitella is most abundant at one level at the top of the clay of SU3 at 1 56 m, rare throughout the middle and shows a small peak in numbers at the base of SU 3 at 2-02 m. The only other appearance of this taxon is in the short marly clay-mud layer at approximately 2*94 m in SUl. Tolypella is confined to this last mentioned position. Qualitative diagram {Fig. 8). Many of the records between 1-50 and 2*50 m have rings round them, indicating that they come from the short duplicate core (only records from the duplicate core that are new to the level are shown ringed). In most cases, e.g. Homalothecium nitens, Minuartia rubella, Papaver section scapiflora, the records simply extend or fill in the gaps of those from the first core. However, for a few taxa, e.g. Sphagnum section Acutifolia, S. recurvum and Hylocomium splenders, the majority of the records 1 50 and 2 50 m come from the duplicate core. In any interpretation it is always dangerous to place weight upon the absence of a taxon from any particular level, and for the last mentioned taxa it is obviously impossible to say much from their pattern of occurrence. For most of the taxa, the problem is not too great and, in the cases of angiosperms, gymnosperms and pteridophytes, the macrofossil records can for the most part be viewed in the light of pollen and spore data from the same core. Microfossil evidence may show the continued presence of a taxon where macrofossil evidence shows only sporadic occurrences due to chance fossilization. The main points of the diagram are as followed. The lower grey clay (3-20 to 2-96 m, part of SUl), although it appeared sterile to the naked eye, yielded several interesting macrofossils. Sphagnum sect. Acutifolia was frequent, along with small portions of Salix sp. (not herbacea), Gramineae, Artemisia sect, dracunculus, Scirpus lacustris, Papaver sect, scapiflora, Aulacomnium palustre and Drepanocladus revolvens. Ostracod remains occurred frequently between 3 00 and 310 m, a depth which encompassed a small band with marly nodules. This ostracod layer occured slightly below the layers of Tolypella and Nitella abundance (2-90 m), which was so obvious in the quantitative study. Macrofossils of Potamogeton (leaves and anthers) made their first appearance in clay between 2-85 and 1-80 m in SU 2 and continued to be present for a large section

20 360 J. A. WEBB AND P. D. MOORE ^" 1-21 SU L L SU 3 L 2 0- a. Q SU L L 3 0 L L UUU L L L L L Numbers per ml sediment SU 1 Fig. 7. Quantitative macrofossil data from Beanrig Moss, core 5C- Only abundant taxa are shown. of the marly clay mud above this. Fruit stones of Potamogeton praelongus between 2-60 and 2-40 m suggests that this is the main species responsible for the leaves and anthers. The appearance of P. praelongus and Salix herbacea macrofossils together in the same sample at 260 to 255 m should be noted. Other features of this macrofossil diagram are that between 2 50 and 2-00 m of SU 2 (detritus mud) achenes and leaf fragments of Dry as octopetala were found in every sample, although the highest number of achenes (12) came from sample

21 Vegetational history of the Whitlaw Mosses E 12- o. Q Hn fl SU fs LfS ex 1-6- fl l-s fs f s SU L L L L L fs t-l f I,cp t-s >s Bs f L f s B fste f s fs f f S fn &s fs fs (-1 SU l-n fs t-lh-' I an -a,bs 2-6-,an L L SU L L uuu L L L L L Fig. 8. Qualitative macrofossil diagram from Beanrig Moss, core 4C. Records that are ringed come from the short duplicate core 0-50 to 2^50 m (only records from the second core that are new to the level are shown ringed), a, Achene; an, anther; b, branch; bs, bud scale; c, cone; cp, capsule; cr, caryopsis: cs, cone scale; ct, capitulum; ex, calyx; fr, fruit; fx, fruit stone; 1, leaf; m, megaspore; n, nutlet; s, seed. Records are from contiguous samples, each with a volume of approximately 30 ml. Continued. 13 ANP 91

22 362 J. A. WEBB AND P. D. MOORE SU a. (U Q * H SU L I- f- f-.fr l-s fl 2 2- ha t-a SU a L L SU Fig. 8 continued.

23 Vegetational history of the Whitlaw Mosses SU U a. O 1 4' B SU SU 2 L L.sh SU ' L L \J\J. L L L L L L L LV Fig. 8 continued.

24 364 J- A. WEBB AND P. D. MOORE 2-40 to 235 m. Between 2-60 to 2-55 m and 2-40 to 2-35 m respectively a complete leaf and a leaf fragment of Vaccinium vitis idaea were found. Remains of Betula nana (leaves, fruits and cone scales) occurred abundantly between 2*30 and 2-20 m (pollen zone BRM-ag) where the deposit has a decreased marl content, also becoming silty. Several cone scales were found between 2 30 and 2*25 m, that had the appearance associated with those of hybrids between Betula nana and one of the tree birches (B. pubescens, B. pendula). Only one rather poorly preserved Betula fruit is assigned to the species B. pubescens. The first macrofossils of Tortellafragilis and Minuartia rubella were found between 2 30 and 2*25 m (pollen zone BRM-ag). Homalothecium nitens has frequent occurrence between and 2*25 m (pollen zone BRM-b). Among many other records of taxa from this section of SU2 the mosses Cratoneuronfilicinum, C. commutatum, cf. Rhytidium rugosum and Thuidium sp. deserve mention along with the leaf and male cone oi Jfuniperus, the fragments of Helianthemum leaf and the seed of Arabis cf. hirsuta. In the clay of SU 3 (pollen zone BRM-c) macrofossils of many taxa are seen for the first time, e.g. Oxyria digyna, Saxifraga granulata, Draba sp., Saxifraga sp. Cerastium, Rhacomitrium cf. canescens. Others which have been of sporadic occurrence now appear regularly, e.g. Salix herbacea and Papaver sect, scapiflora. Some taxa appear only at the boundaries of the clay (Potamogeton filiformis, Empetrum sp., Erica tetralix, Rumex acetosella) but there are insufficient records to interpret the pattern of occurrence. From the concentration diagram it can be seen that Nitella also occurs at these boundaries. The upper detritus mud SU4 shows an impoverished fiora compared with the upper clay SU3. Blackpool Moss (Fig. 9) A qualitative macrofossil diagram is available for the deepest sediments from one core at this site. It must be noted that the macrofossil sequence does not come from the same core as the one used for the pollen analysis (Fig. 4, position H) but from a core taken 25 m away at I. For many of the taxa found there is no clear pattern of occurrence but it is obvious that some, e.g. Salix herbacea and Nitella, are present continuously in the clay (4-55 to 5-15 m) of SU3 (pollen zone BPM-c) and sporadically in the other sediments; whereas others, e.g. Daphnia, Cristatella, Ditrichum flexicaule, Bryum sp. show the converse pattern. Of especial interest in Core I are the records of seeds referred to - Silene acaulis and Saxifraga rivularis or S. cernua. These records provide important confirmation of pollen identifications of these taxa from Core H. It is noted that the finds of Tortella fragilis at Blackpool Moss are very similar in distribution (i.e. around the lower boundary of the upper clay) to the finds of this species in the core from Beanrig Moss. The absence of Tolypella from this diagram is probably due to the fact that no samples of the basal sediments of Core I could be taken due to the stiffness of the sediments. Tolypella was found in the basal sediments of a complete core taken from shallower parts of the Blackpool Moss basin. Fig. 9. Qualitative macrofossil diagram from the bottom sediments of core I Blackpool Moss. Abbrevations as in Figure 8, excepting the following: ep, epibippum; he, head capsule; o, oospore; st, statoblast; t, test. Records are from contiguous samples, each with a volume of approximately 30 ml.

25 Vegetational history of the Whitlaw Mosses Depth ( m ^ SU " 4-5 SU f 4- f 4- f f 50 SU

26 366 J. A. WEBB AND P. D. MOORE DISCUSSION Possible age of the sequences described The results here described obviously indicate a Late Devensian Late-glacial age (13000 to B.P.) for the sediments in spite of the lack of radiocarbon dates (hindered by the calcareous nature of the sediments). The presence and distributions of selected indicator fossils such as Salix herbacea, Papaver sect, scapifiora, Artemisia type-a {A. cf. norvegica), Potamogeton praelongus and Betula pubescens, whose present-day habitat requirements are known (see Dahl, 1951; Iversen, 1954; Clapham et al., 1962) indicate that the 'upper clay' at both sites (1-50 to 2-02 m, SU3, pollen zone BRM-c in Beanrig; 5-55 to 610 m, pollen zone BPM-c in Core H, 4-55 to 5-15 m. Core I, Blackpool Moss) was deposited during a temporary cold period (stadial) after a temporary warm period (interstadial). The latter is represented by the detritus muds beneath the clay layer, e.g. SU 2 at Beanrig Moss. The stadial which is most likely to be represented by the upper clay is the Loch Lomond stadial which is correlated with the Younger Dryas stadial (Jessen zone III, see Jessen and Farrington, 1938) in Europe. This is suggested by Mangerud et al. (1974) to have occurred between ^^C years B.P. and i*c years B.P. although dates for the sedimentological change at individual sites might be expected to differ. The muds below these clays contain warmth-loving taxa and were probably deposited during the widely recognized Late-glacial interstadial (see Gray and Lowe, 1977) which covers a time span of (or 14000) to ^^C years B.P. (depending on definitions). The interpretation of fossil assemblages in terms of habitat mosaics The problems associated with the interpretation of pollen and macrofossil assemblages from the Late Devensian are well known (e.g. West, 1964). Before any interpretation of the vegetational history can progress, an attempt must be made to isolate the original species groupings involved. Examples of this sort of approach are the works of Moore (1970) and Burrows (1974) where the fossil taxa are placed into communities with regard to the present ecology of the species involved. To clarify the position when a fossil taxon includes genera or species which may occur in several different communities, the possible genus or species involved in the community is placed in brackets after the fossil taxon. Thus, for example; and Filipendula sp. (e.g. F. ulmaria) in 'Carr or marsh' Filipendula sp. (e.g. F. vulgaris) in 'Base-rich, well-drained short turf. It is to be noted that this notation is not intended to imply that the species or genus in brackets has been identified from the sites discussed here. By the combination of microfossil and macrofossil data in this classification, it is hoped to improve the definition of the communities proposed (see Table 1). In certain cases some difficulty has been experienced in differentiating taxa which have similar habitat requirements, but different temperature requirements, in that some are found today at low altitudes and latitudes and others in these habitats at high altitudes or latitudes. In cases such as these the ones requiring (or tolerating) colder conditions are separated into a subgroup of their own (see group D as an example). They are not separated completely because it is noted that, in the sediments, taxa representing both high altitude and low altitude examples of

27 Vegetational history of the Whitlaw Mosses 367 Table 1. Examples where macrofossil identifications have supported {and in most cases increased the accuracy of) pollen identifications at the Whitlaw Mosses Macrofossil taxon Betula nana B. cf. pubescens Cerastium sp. cf. Cardaminopsis petraea* Arabis sp.* A. cf. hirsuta* Dryas octopetalaf Erica tetralixf Vaccium vitis-idaea cf. Helianthemum sp.* Juniperus communis* Minuartia rubella Myriophyllum sp.f Oxyria digyna* Papaver sect, scapiflora Ranunculus sect. Batrachium Salix herbaceaf Salix sp. (not herbacea)f Saxifraga cf. granulata S. rosacea/hypnoides S. oppositifolia* S. cf. rivularis } Corresponding pollen taxon Betula nana-type Betula Cerastium-type Cruciferae Dryas octopetala Ericaceae Helianthemum Juniperus Arenaria-type s.s. and s.l. Myriophyllum alternifiorum M. spicatum M. verticillatum Oxyria-type Papaver Ranunculus-type Salix Saxifraga granulata-type S. oppositifolia S. cernua/rivularis * Cases where occurrence of the macrofossil is accompanied in the same sediments by relative abundance of the corresponding pollen taxon. t Cases where occurrence of the macrofossil is not accompanied in the same sediments by relative abundance of the corresponding pollen taxon. a similar habitat occur together, such as Hedysarum cf. hedysaroides and Scabiosa sp. in 'base-rich well-drained short turf. These two may have occurred in the same community in the Late Devensian. Taxa which have a rather wide occurrence (e.g. Hylocomium splendens) have been placed under the communities in which they are most commonly found today, rather than in all the ones in which it is possible that they could have lived. This inevitably leads to an over-simplifed picture of the vegetation. One example of this is the group of taxa placed in Group J under the heading ' acid peaty soils or bogs'. The findings of fossils (especially macrofossils) of such taxa in highly calcareous sediments is rather difficult to explain. The taxa involved occur most commonly on acid peaty soils or bogs, but they can also be found in what appear to be very unlikely situations, for example, Calluna vulgaris and Erica tetralix grow on the incipient oligotrophic grassy hummocks in the calcareous flush areas of the present vegetation around Murder Moss. The existence of such a situation during the Late Devensian cannot be ruled out, especially when the substantial representation of other taxa in the 'flush' community (Group G) is considered. The communities envisaged in the vicinity of the Whitlaw Mosses during the Late Devensian are as follows.

28 368 J. A. WEBB AND P. D. MOORE GROUP A Birch Scrub Betula pubescensy Dryopteris filix-mas-type (e.g. D. filix-mas) Crataegus-typ^ (e.g. Crataegus, Sorbus aria) jfuniperus communis (in communities transitional to C.) cf. Frangula alnus, Hylocomium splendens. GROUP B Juniper Scrub jfuniperus communis [the Juniper community at the Whitlaw Mosses does not appear to be related to the fern-rich ones described by Pigott (1956), McVean and Ratcliffe (1962), but perhaps has greater affinities with those on the drier soils of the chalk downs]. GROUP C Base rich, well-drained short turf {mostly closed, but often with a small amount of bare ground) Gramineae, Cyperaceae, Helianthemum, sp., Lotus sp. (e.g. L. corniculatus), Poterium sanguisorba, Dianthus sp., Ononis-type (e.g. Ononis), Astragalus danicustype(e.g. A. danicus), Mentha-type{e.g. Thymus), Campanula-type {e.g. Campanula, Phyteuma) cf. Jasione, Rubiaceae, Compositae, Scabiosa (e.g. S. columbaria) cf. Fchium, Cerastium-type (e.g. C. pumilum), Filipendula sp. (e.g. F. vulgaris). Ranunculus-type, Cirsium sp. (e.g. C. acaulon), Potentilla-type (e.g. P. tabernaemontani or Fragaria), Rhinanthus-type (e.g. R. minor), Centaurea nigra-type, Gentianella cf. amarella, Arabis cf. hirsuta, Linum catharticum-type (e.g. L. catharticum) cf. Medicago falcata, Medicago arabica/lupulina, Botrychium sp., Ophioglossum, Thuidium sp. (e.g. T. abietinum, T. recognitum), Hypnum cupressiforme, Campylium cf. chrysophyllum, Fissidens adianthoides, Ditrichum fiexicaule, cf. Rhytidium rugosum, Hylocomium splendens. Also included within this community are the following taxa which today are found in such short turf communities at high altitudes (e.g. subalpine grassland). Dryas octopetala. Astragalus danicus-type (e.g. Oxytropis campestris), Hedysarum cf. hedysaroides, cf. Astragalus alpinus, Rhinanthus-type (e.g. Bartsia alpina), Gentiana cf. verna, Polygonum bistorta-type (e.g. P. viviparum), Potentilla-typt (e.g. P. crantzii), Lycopodium selago, L. alpinum, L. clavatum, Distichium sp. (e.g. D. capillaceum). GROUP D Bare ground, i.e. disturbed rocky soil, sand, gravel or shingle Chenopodiaceae, Arenaria-type s.s. (e.g. A. serpyllifolia, Minuartia hybrida) cf. Anagallis, Plantago major, Polygonum aviculare, Silene vulgaris-type (e.g. S. vulgaris), Sedum acre-type (e.g. S. acre, S. album). Taraxacum sp., Cerastiumtype (e.g. C glomeratum, Stellaria media), Artemisia cf. maritima s.l. (inland, non-saline forms living on dry calcareous sub-strata - see Persson, 1974), Artemisia cf. campestris, Urtica-type (e.g. Parietaria), Hippophae rhamnoides, Fphedra distachya-type, Draba sp. (e.g. D. muralis), Agrimonia sp., Oxyria-type (e.g. R. crispus), Rumex acetosa, R. acetosella, R. obtusifolius-type (e.g. R. obtusifolius), Potentilla-type, Gypsophila fastigiata/repens (e.g. G. fastigiata - see Albertson, 1950; Sterner, 1938), Hypnum cupressiforme, Polytrichum sect, juniperina (e.g. P- juniperinum), Tortula sp., Tortella sp., Tortella fragilis (see Holmen, 1959), Barbula sp., Fncalypta sp., Bryum sp., Pohlia sp., Rhacomitrium cf. canescens, Ditrichum fiexicaule. Also included in this community are the following taxa which today are found in open communities at high altitudes. Some taxa descend to low levels in the North (e.g. fell fields in Greenland, Iceland, northwest Scotland, Norway).

29 Vegetational history of the Whitlaw Mosses 369 Silene acaulis, Papaver sect, scapifiora, Artemisia cf. norvegica, Minuartia rubella, Arenaria ciliata, Armeria maritima, Plantago maritima, Saxifraga rosacea/hypnoides, S. oppositifolia cf. Cardaminopsis petraea, Salix herbacea*, Draba sp. (e.g. D. incana, D. norvegica), Lycopodium alpinum, L. selago. Lychnis viscaria/alpina (e.g. L. alpina), Oxyria-type (e.g. O. digyna), Cerastium sp. (e.g. C. alpinum), Distichium sp. (e.g. D. capillaceum*), Polytrichum norvegicum*, P. alpinum*. Taxa marked with an * are especially characteristic of areas with prolonged snow^-lie (see Gjaerevoll, 1950). GROUP E Dwarf shrub heaths Dry as octopetala, Empetrum sp., Betula nana, Salixsp. (dwarf types), Vaccinium vitis-idaea, cf. Rhytidium rugosum, Homalothecium nitens (see Dickson, 1973). This community undoubtedly grades in to that of D. GROUP F Short turf calcareous flushes and springs or wet rocks Selaginella selaginoides, Parnassia palustris, Saxifraga cernua/rivularis, Sedum acre-type{g.g. S.villosum), Thalictrumsp.{e.g. T.alpinum),Linumcatharticum-type (e.g. L. catharticum), Epilobium sp., Scorpidium scorpioides, S. turgescens, cf. 'Weissia^ (e.g. Gymnostomum aeruginosum or Eucladium verticillatum), Drepanocladus revolvens, D. uncinatus, Ctenidium molluscum, Cratoneuron cf. commutatum, Cratoneuron filicinum, Acrocladium giganteum, Barbula sp. (e.g. B. tophacea), Philonotis sp., Pohlia sp. (e.g. P. wahlenbergii v. glacialis and others). This community grades into that of G. GROUP G Fens and marshy lake margins Potentilla palustris, Salix sp., Geum cf. rivale, cf. Frangula alnus, Betula pubescens, Filipendula sp. (e.g. F. ulmaria), Valeriana sp., Thalictrum sp. (e.g. T. fiavum), Symphytum sp., Umbelliferae, Succisa pratensis, Cirsium sp. (e.g. C. dissectum, C. palustre) Rumex obtusifolius -type (e.g. R. aquaticus, R. hydrolapathum), Caltha-type (e.g. C. palustris), Sanguisorba officinaiis, Polypodiaceae, Carex sp., Thelypteris palustris-type (e.g. T. palustris), Carex sp., Carex rostrata, Equisetum sp., Menyanthes trifoliata, Scirpus cf. lacustris, Typha latifolia, T. angustifolia-type. Many of the mosses present in G occur in the present group as well, notably: Scorpidium scorpioides, S. turgescens, Drepanocladus revolvens, Bryum sp., Cratoneuron cf. commutatum, C. filicinum, Acrocladium giganteum, Philonotis sp. Other mosses not placed in H, but which occur here are Homalothecium nitens, Aulacomnium palustre, Paludella squarrosa, Mnium cf. pseudopunctatum, Drepanocladus fluitans, D. cf. aduncus, Fissidens adianthoides, Spagnumpalustre. Sphagnum recurvum. GROUP H Damp tall-herb meadows {cf. McVean and Ratcliffe, 1962) Valeriana sp., Filipendula sp. (e.g. F. ulmaria), Geum cf. rivale, Thalictrum sp- (e.g. T. fiavum), Saxifraga granulata, Trollius europaeus, Saussurea alpina, Sedum cf. rosea, Umbelliferae, Epilobium sp. (e.g. E. angustifolium), Succisa pratensis, Cirsium sp. (e.g. C. heterophyllum) cf. Swertia perennis. cf. Anemone (e.g. A. nemorosa), Urtica-type (e.g. Urtica), Sanguisorba officinaiis, Rumex obtusifoliustype (e.g. R. obtusifolius), Hylocomium splendens, Fissidens adianthoides.

30 37O J. A. WEBB AND P. D. MOORE GRO UP I Lake water {plants for the most part immersed) Nymphaea sp., Myriophyllum alternifiorum, M. spicatum, M. verticillatum Potamogeton praelongus, P. filiformis, P. cf. gramineus, Chara sp., Nitella sp., Tolypella s.p. Ranunculus sect. Batrachium. GROUP y Acid peaty soils or bogs Erica tetralix, Polytrichum commune. Sphagnum sect, acutifolium, Vaccinium vitis-idaea, Empetrum sp., Calluna vulgaris. The inferred vegetational history of the sites during the Late Devensian Beanrig Moss The vegetational events inferred are summarized in Table 2. From 3-20 to 2-40 m the only type of evidence of past vegetation is macrofossils, pollen grains being much too sparse in the sediments for counts to be made. In the clay below 310 m remains are very scarce, but communities from edges of marshy hollows are indicated by the moss remains and dry disturbed ground by an Artemisia capitulum (Fig. 10). There are no firm temperature indications in these finds although the clay sediments indicate a period of downwashing over surrounding slopes which were, at most, poorly vegetated. Such a situation is more common under cold climates. The first indication of warming in the lake water is at 3-10 m where the precipitation of marl was encouraged and ostracods thrived in the lake. Table 2. Summary of the vegetational changes during the Late Devensian at Beanrig Moss Assemblage zones, subzones and their dominant pollen taxa BRM-e Juniperus-Betula-Empetrum BRM-d Gramineae /?uwex Cyperaceae BRM-c Artemisia Oxyria Cyperaceae BRM-C2 Artemisia-Oxyria-Cerastium BRM-Ci Artemisia-Oxyria-Artemisia Helianthemum Juniperus -Gramineae Helianthemum-Betula-Gramineae BRM-a^ Betula Salix Rumex BRM-a, Salix-Rumex- Myriophyllum alternifiorum Inferred vegetation Juniper and tree birches form 'parktundra' with some heath area. Openground communities restricted. Lake water shallow Rumex acetosa-rich grasslands with Empetrum heaths. Aquatic plants flourishing Bare-ground communities dominant. A mosaic of: (i) Artemisia norvegica and associates in wind-exposed areas (ii) Salix herbacea and associates in areas of long snow lie. Aquatic flora poor Helianthemum-dominated, dry, open grassland with sparse Juniper scrub and small areas of dwarf shrub heath Expansion of dry grasslands and Juniper scrub Betula nana/dryas dwarf-shrub heaths with scattered tree birch; some grassland and bare ground communities Sparse willow and tree birch scrub intermixed with Betula nana/dryas dwarf-shrub heaths and Rumex acetosa grasslands. Aquatics flourish

31 Vegetational history of the Whitlaw Mosses mm Fig. 10. Drawing of capitulum of Artemisia sect, dracunculus found in a sediment sample between 3.20 and 3-30 m depth at Beanrig Moss. The accompanying land plant taxa [Gramineae, Salix sp. (not herbacea), Scirpus lacustris, Arenaria ciliata and Papaver sect, scapiflora^ indicate a cold, open, partly marshy tundra with degree of bare soil. Between 2*95 and 2*55 m there is evidence that the lake water community was flourishing, dominated by Nitella and Tolypella sp. with Daphnia and Chironomidae present. The species most likely to have been involved in the early Tolypella peak is T. glomerata, recorded from early interstadial sediments from Sweden by Berglund and Digerfeldt (1970). They note that the species has a pronouncedly southern distribution in Sweden, but apparently this is not so in Britain (Groves and Bullock-Webster, 1920). Definite evidence for the warm climate associated with an interstadial was not found until 2*60 m, where the Potamogeton species which replaced the charophytes in the lake water vegetation was determined as P. praelongus, an accepted thermophile often recorded in the Boiling interstadial (Iversen, 1954). At Beanrig Moss it would appear that the macrophytes behaved in the way that Iversen suggested, i.e. they were the first to respond to warmth because of their fast rate of spread (many are known to be carried by animal vectors, see Love, 1963). Aquatic macrophytes also act efficiently as pioneers in that they have no requirement for a mature soil. The presence of Salix herbacea around the lakes at this time gives climatic evidence that conflicts with that of the Potamogeton. S. herbacea is often used as evidence for cold conditions, as it is today commonly found in areas of long snow-lie at high altitudes, e.g. Gjaerevoll, (1950). The evidence of McVean (1955) shows that it is not restricted to this habitat, as he records it covering large tracts in Iceland, often appearing at sea level. It is conceivable that it could have persisted in warmer conditions in the absence of competing warmth-loving, dry-land plants. The period of greatest Potamogeton abundance is between 2-75 and 2-40 m, in the most marly section of the interstadial sediment. It is thought that this very marly section was deposited during the warmest part of the interstadial. Later on in the interstadial, Myriophyllum alterniflorum and Ranunculus sect. Batrachium replace Potamogeton in the lake community. From 2-60 m upwards, the Dryas achenes, Vaccinium vitis-idaea leaves and cf.

32 372 J. A. WEBB AND P. D. MOORE Rhytidium rugosum leaves suggest the local presence of dry land of group E (the dwarf-shrub heaths) and the moss genera Ditrichum, Distichium, Tortula and Barbula suggest that a certain amount of bare ground (Group D) was present. From 2-36 m upwards, pollen evidence is available and immediately it can be seen that Group A (fens and marshy lake margins) is as well represented by pollen as by macrofossils in zone BRM-a. The high percentages of Salix may be taken as evidence of extensive stands of willow (see the surface pollen studies of van der Hammen (1951) and Fredskild (1967). One cannot preclude the possibility that this Salix pollen came from the dwarf willows of Group E, but the macrofossil evidence of tree-willows makes it likely that here were marsh and fen communities, possibly on the lake margins, and/or willow thickets in damp hollows nearby. The high amounts of Rumex acetosa-\- acetosella, which accompany the Salix peak, are more difficult to interpret. Due to its high pollen productivity, Rumex acetosa is consistently over-represented in surface pollen studies (e.g. Birks 1973 b) and its wide ecological tolerance makes it possible that it could have been growing in either of communities H or D. At this time of Salix abundance, small amounts of tree Betula and B. nana are present, the former perhaps as isolated trees or copses, the latter with Dryas in the Group E dwarf shrub areas. Juniperus would also have been present but not abundant. Small amounts of Artemisia (indeterminate) and the presence of Rubiaceae and Ophioglossum confirm the macrofossil evidence of open-ground communities (D). In contrast to its macrofossil record, Dryas is very poorly represented in the pollen spectrum (2% total pollen); but it is noted that such low values can be found in surface pollen samples under Dryas dominated vegetation (e.g. Rymer, 1973) and it is therefore reasonable to suggest substantial Dryas coverage at this time. The lake fiora during BRM-a was dominated by Myriophyllum alterniflorum and Potamogeton, but they are diminished in importance above this zone. Either a fall in temperature or shallowing of the lake water could have had this effect. Dwarf birch is more abundant in subzone BRM-ag as more pollen and many macrofossils of it occur despite an increase in tree birch pollen. One fruit of B. pubescens and two cone scales of hybrids between dwarf and tree birch were found, the latter indicating that B. nana was probably still present. Perhaps there were individuals of tree birch amongst quite extensive dwarf shrub communities on the drier slopes around the Beanrig Moss basin. A similar frequency of Betula nana in interstadial sediments is reported from Bornholm by Iversen (1954). During BRM-dg Homalothecium nitens dominates the moss remains and it is tempting to suppose that it was here occupying the more unusual habitat of the ground layer in a dwarf shrub heath (see Dickson, 1973), Group E, rather than its more characteristic habitat in Britain today, which are fens and fiushes (Groups F and G). These last mentioned habitats were in existence at this time as is evidenced by Pedicularis, Parnassia, Geum cf. rivale, Cratoneuron and Philonotis. During BRM-a2 there is a slight increase in taxa of Group D (the bare ground indicators); notable amongst these are Saxifraga oppositifolia, Papaver sp., Ephedra distachya type, Artemisia type-b, Minuartia rubella and Tortella fragilis (see Fig. 11). It will be noted that some of these taxa are cold tolerant although they are not definite indicators of cold conditions. Dry basic short turf is also present during BRM-ag. The occurrence of cf. Medicago falcata suggests that this grassland could be likened to the 'Stipa tussock steppe' or 'meadow steppe' of Keller (1927) and several types of 'continental grass-heaths' described by Meusel (1940).

33 Vegetational history of the Whitlaw Mosses mm I mm Fig. 11. Drawing of macrofossil of Tortella fragilis (Hook & Wils) Limpr., found in a sediment sample between 1-90 and 1-95 m depth at Beanrig moss. For the records of Lonicera in this subzone, it is impossible to ascertain what species and therefore what community may be implicated. Zone BRM-b, the last zone of the interstadial, was a time when jfuniperus expanded to a level where scattered patches of well grown scrub with still plenty of bare ground and dry grassland between the patches are indicated. The Frangula alnus record for this zone may mean that this species was living alongside the jfuniperus as has been suggested by Berglund (1966) on the basis of records of Frangula from the late glacial of south Sweden. Dry grassland is here indicated by Group C members and would appear to have been dominated by Helianthemum which is present in substantial amounts, considering the low capability of the genus for pollen production and dispersal. It is present at a maximum of 8 % TP (12 % total dry land herb pollen); these percentages are comparable to ones found by Proctor and Lambert (1961) in surface pollen samples under Helianthemum dominated grasslands in Ireland and France. It is suggested that during zone BRM-b, Beanrig Moss received most of its pollen input from just one community; Helianthemum-rich short grassland. Only a few other pollen diagrams from this period show Helianthemum values as high as the ones described from Beanrig Moss, the majority of sites having much less than 5% of the non-tree pollen. The exceptions are Blackburn (1952), who records Helianthemum as 10% of total pollen from interstadial sediments at Neasham, Co. Durham; Lang (1951), who records it at 20% of total pollen in a Lower Dryas spectrum from southwest Germany; and Singh (1970), who records

34 374 J. A. WEBB AND P. D. MOORE ectoaperture endoaperture 33-5 /i.m (b ectoaperture endoaperture ectoaperture endoaperture Fig. 12. Sketches of fossil Artemisia pollen grains. Type A grain identical to A. norvegica. (b) Type A grain with the more strongly defined pori and shape of A. pontica, but echinae characteristic of A. norvegica. (c) Grain which was placed in type-b and was identified to grains of A. maritima ssp. maritima. Continued.

35 Vegetational history of the Whitlaw Mosses ' -' '' ' '., 19 /I m rr \ endoaperture ectoaperture (f) Fig. 12. continued, (d) Grain which was placed in type-c. (e) Grain which was placed in type-e and was identical to grains of A. campestris. (f) The two grains placed in type-f. it as 10% of total pollen from interstadial sediments at Ballydugan, Ireland. Neither Blackburn not Lang recognized Juniperus pollen in their counts, so it is possible that these values may in fact be overestimates in comparison with the present work. Although Dryas pollen is rare in BRM-b, macrofossils are present throughout the zone. It may still be a part of a dwarf-shrub community with Empetrum, or it could be a component of the grasslands. Other taxa which almost certainly belong to the Helianthemum grasslands in this zone are Scabiosa, Dianthus sp., Gentiana cf. verna, Linum catharticum type, Arabis cf. hirsuta, Plantago maritima, Hedysarum cf. hedysaroides and cf. Astragalus alpinus. The three taxa last mentioned are today characteristic of mountain grassland of the ' subalpine' type, but it is possible that they could have been growing alongside Helianthemum species, as members of this genus can be found in turf communities at high altitudes (over 700 m) in the

36 J. A. WEBB AND P. D. MOORE mountains of central and south Europe (Proctor and Lambert, 1961). Astragalus alpinus can occur in less grassy communities, for instance on the calcareous boulder-clay of a landslide in Norway described by Nordhagen (discussed in Iversen, 1954), where it grows with Lotus corniculatus, Plantago media and Rumex acetosella (all species whose presence is indicated in BRM-b). As to the temperature indications in BRM-b, the presence of Astragalus alpinus and Hedysarum sp. may indicate that conditions were cool, if not cold, at this time. It is unlikely to have been arctic because of the presence of Hippophae, which Iversen (1954) regards as fairly warmth demanding, quoting it as rarely reaching the tree-limit and being sterile in the subalpine zone. The occasional finds of Scabiosa pollen in BRM-b could be regarded as evidence for a temperate climate if the species concerned was S. columbaria, which today in Britain has a limited distribution northwards, having only a few posts farther north than Roxburghshire. However, it is not possible to say that this is the species involved, and there are several others, e.g. S. canescens, S. ochroleuca, which have different temperature requirements from S. columbaria. Another interesting taxon from BRM-b is Gypsophila fastigiata/repens. If the pollen grains were produced by the calcicolous ' continental' species (see discussion later) G. fastigiata (as some authors, e.g. Iversen, 1954, Berglund, 1966, appear to assume for their records) then the parent plants may have grown in a rather open version of the base-rich short turf community (C), rather similar to that which today exists on the Swedish island of Oland (see lists in Du Rietz, 1923, Sterner, 1938; Albertson, 1950). However, if the pollen grains were produced by the calcicolous alpine species G. repens, then a rather different community is indicated. G. repens, although occasionally found in some high-level grasslands dominated by Sesleria coerulea, most commonly grows in high level pioneer communities on sandy or rocky soil (see descriptions in Meusel, 1940). It is recorded in association with Helianthemum species, but not as frequently as is G. fastigiata. If G. repens were present it was most probably a member of Group D. Other taxa in this zone which certainly belong to Group D are Hippophae and Artemisia-types A, B and D. However, from the low amounts present, it is reasonable to suppose that disturbed ground occupied only a small proportion of the landscape at this time. The presence of Artemisia type-a (A. cf. norvegica) and Saxifraga oppositifoua in BRM-b.2 reinforces the idea that the climate was cool if not cold. Flush and fen communities are perhaps important locally during this zone as indicated by the continued occurrence of Homalothecium nitens and Cratoneuron filicinum, and the appearance of Selaginella. Although once again, Homalothecium nitens may be occupying the shrub heath community mentioned earlier. Erica tetralix is conspicuous in the macroscopic remains from BRM-b2, but in this subzone there is no pollen evidence of any Ericaceae, all the Ericales tetrads proving to belong to Empetrum. The increased representation of these two taxa in BRM-ba may mean that in the last stages of the interstadial, leaching had progressed to such a point that typical acid-loving species (Group J) could expand. This conclusion is rather difficult to uphold in view of the findings oi Helianthemum and Gypsophila in the same sediment as the Erica tetralix leaves. However, the findings can be reconciled by supposing that leaching may have been a very local feature of the topography, for example, confined to small hummocks in the marginal fiush areas. The aquatic fiora of BRM-b seems markedly impoverished compared to that of BRM-a. Potamogeton, Chara, Myriophyllum alterniflorum and Ranunculus sect.

37 Vegetational history of the Whitlaw Mosses 377 Batrachium are present in trace amounts only and it may be that their low productivity (giving a slow sediment accumulation rate) accounts for the increased concentration of pollen grains in this zone. This low productivity and the increased silt content of the sediments could be a result of the cooler climate indicated by members of the land flora. At, or just before, the junction of BRM-b with BRM-c, the appearance of many taxa together heralds the arrival of difterent habitats and communities that existed during the cold climate of the Loch Lomond stadial. Pediastrum and Nitella seem to profit from the conditions during the brief transition period between the two zones. Such a peak in Nitella at the beginning of the stadial has been noticed by Berglund and Digerfeldt (1970) Vasari and Vasari (1968) regard the higher values for Nitella in such situations to be a result of solifluction bringing leached surface layers into a lake. However, to explain the Pediastrum response it would be necessary to postulate that increased erosion and down wash brought more nutrients to the lake than was the case before, and this does not seem compatible with the Nitella evidence. As to the land plants of BRM-c, there is a certain danger in interpreting the sudden appearance of macrofossils of a taxon in the sediments as indicative of the arrival of the parent plant in the locality. It may be that as solifluction and downwash increased, fruits, leaves and seeds appeared in the sediments for the first time, although the parent plants may have been growing in the area prior to the onset of such conditions. The macrofossils of Rumex acetosella, Oxyria digyna, Saxifraga oppositifolia and Papaver sect, scapiflora, which appear at the junction, may be examples of this, as these taxa all have pollen occurrences in the interstadial sediments. In zone BRM-c it is evident that Group D (the bare ground communities) dominates the scene. Thejfuniperus scrub and Helianthemum dominated grasslands have gone and have been replaced by communities in which the following taxa are prominent: Cruciferae, Thalictrum, Oxyria digyna, Ditrichum flexicaule, Distichium sp., Saxifraga oppositifolia, S. hypnoides/rosacea, Salix herbacea, Cerastium type, Artemisia type-a {A. cf. norvegica), Arenaria type s.l., Minuartia rubella and Papaver sect, scapiflora. It is easy to over-estimate the importance of, for example, Oxyria and Thalictrum in the vegetation, as these two are fairly abundant pollen-producers. On the other hand, Saxifraga oppositifolia and the species within Arenaria-type and Saxifraga granulata-type probably occupy more of the vegetation than their sparse pollen records would suggest (see Birks, 1973a). The pollen grains in Artemisia type-a compare closely with Artemisia norvegica (see Appendix) and it can reasonably be assumed that this species was an important component of the BRM-c vegetation. A. norvegica is a poor pollen producer and yet is present in substantial percentages in the pollen diagram. In his studies of niodern pollen spectra from surface vegetation, Birks (1973a) reports that A. norvegica was found in pollen spectra only when it was locally present in his sampling plots, and then only at values up to 9 5 % of total pollen. At Beanrig Moss in BRM-c values for Artemisia type-a of up to 12 % of total pollen are recorded. It is possible that surface samples from moss polsters may be misleading when compared with samples from lake sediments, as in the latter case a large proportion (perhaps as high as 80 % - Bonny, 1978) of the pollen will have originally landed on the soil around the basin and been subsequently washed in. It is felt that this adequately explains these high values. McVean and RatcliflFe (1962), in their study of Scottish Highland vegetation.

38 378 J. A. WEBB AND P. D. MOORE quote A. norvegica as being restricted to 'exposed montane summit heath' and in particular to the markedly chionophobous Juncus trifidus Festuca ovina nodum. Extensive solifluction is a feature of this facies. Several of the species quoted as associates of A. norvegica can be detected in zone BRM-c, e.g. Salix herbacea, Polytrichum alpinum and possibly Cherleria sedioides {'Arenaria-type s.l.'). However, there are several points of difference between th^ejuncus trifidus Festuca ovina nodum and the BRM-c fossil assemblage, notably the abundance of Rhacomitrium lanuginosum in the former and its absence in the latter. Another interesting association containing A. norvegica is quoted by Gjaerevoll (1963) from the Gjevilvasskammene Mountains in TroUheimen, south Norway. Here the substrate is disintegrated mica schist on the mountain top. Associates of A. norvegica are (amongst others) Papaver radicatum, Minuartia rubella, Draba fiadnizensis and Draba lactea. This community probably has more affinity with the BRM-c A. norvegica community than does that described by McVean and RatclifTe. Papaver species of the section scapiflora {e.g. P. radicatum, P. alpinum, P. nudicaule) are typically members of exposed, stony 'fell-field' such as occurs in Iceland and Greenland. The combination of these poppies with Artemisia norvegica strongly suggests that during BRM-c there would have existed, somewhere in the vicinity of Beanrig Moss, areas with exposed, wind-blasted mineral soil which was subject to very little snow-lie. This may point to the fact that during the stadial, conditions were very dry as well as very cold. However, other taxa from BRM-c indicate the presence of more chionophilous communities. Salix herbacea is well known for its abundance in areas where snow lies well into the late spring and Iversen (1954) regards Oxyria digyna as a snow-patch plant. Other taxa which are commonly found in this habitat and are represented in BRM-c are Distichium sp., Polytrichum alpinum and P. norvegicum. Of all these, only the last mentioned is actually confined to snow-beds, being typical of beds at the highest altitudes which are exposed latest in the year (see McVean, 1955; Gjaerevoll, 1950). P. norvegicum and S. herbacea are perhaps more typical of snow-beds on soils poor in lime, but have been recorded from calcareous ones. Pennington (1980) has described vegetation mosaics from Greenland in which Artemisia borealis dominates wind-swept ridges among which are found areas of heath and snow-patch communities. Such a mosaic can develop in a region of undulating topography if high winds lay bare the more exposed ridges and snow builds up in the hollows. Such an interpretation could be placed upon the results described here. Several taxa from the BRM-c list could equally well have occurred in exposed areas or in areas of snow-lie (e.g. Saxifraga oppositifolia, Draba sp. and Cerastium sp.). S. oppositifolia has been found to have a great capacity to withstand water stress and thrives under conditions which approach those of an arctic desert (Teeri, 1973), yet it exists also at sea level on the oceanic west coast of Scotland (McVean and RatclifTe, 1962). Another eurytopic species is Tortella fragilis. This moss is described as a calcicole of rock and sand with a wide Eurasian and North American distribution, extending north to Peary Land (Dickson, 1973), but it is also found on the bare, exposed Alvar of Oland (Albertson, 1950) and also in snow beds on very calcareous soils (Gjaerevoll, 1950). In a case like this it would seem that a calcareous substratum is of far greater importance to the plant than either water availability or temperature. The conclusion of the above discussion must be that the mosaic of communities

39 Vegetational history of the Whitlaw Mosses 379 present on land during BRM-c encompassed great extremes of snow cover and of wind exposure, the distribution of such communities being controlled by local microtopography. It is rather interesting that macrofossils of vegetative parts of Myriophyllum species should occur throughout BRM-c when pollen grains are present in only trace amounts. This could indicate the local persistence throughout the stadial of Myriophyllum species in non-reproductive condition. This in turn would explain the early rise in Myriophyllum alterniflorum at the end of BRM-c, for the plant would not need to re-invade the area and would have responded to a rise in temperature simply by an increase in fiowering. At the point where the Myriophyllum alterniflorum rise is taken to indicate the onset of the Flandrian warm conditions Gust before BRM-d), it is interesting that there is a peak in Nitella and the re-appearance of the taxa which occurred at the BRM-b/BRM-c junction, i.e. Erica tetralix and Potamogeton fluformis. Perhaps here again is evidence of Vasari and Vasari's (1968) 'leached layers' entering the lake water. A few of the land taxa characteristic of zone BRM-c persist into BRM-d and it must be envisaged that the plants grew in the area until either their temperature tolerances were exceeded, or they were competitively displaced by invading species which were successful under the warmer conditions.the cold-tolerant taxa must have become progressively restricted to higher ground, until the situation of southeast Scotland today was reached, where many of the taxa typical of BRM-c (e.g. Oxyria digyna, Sedum rosea, Saussurea alpina, Saxifraga oppositifoua, Salix herbacea) are found in a small area on the Moffat Hills (RatclifTe, 1959) approximately 38 km from the Whitlaw Mosses. Some taxa (Minuartia rubella, Papaver sect.scapiflora, Artemisia norvegica) appear not to have been able to survive in this refuge and are thus absent from the fiora of southern Scotland. Zone BRM-d covers the period when the vegetation was changing quickly and taxa rose to prominence for only brief periods. The indication is of grasslands of rather similar character to those of BRM-b, but differing from those in having more Rumex acetosa and much less Helianthemum. In some places Empetrum heath would have been present, probably with an admixture of Betula nana, but no Dryas is recorded (unlike the BRM-b heath). Although several taxa of northern or 'subalpine' affinities are present (Saussurea, Hedysarum) so also is Typha latifoua, a plant which indicates that the July temperature was above 14 C (Iversen, 1954). During this time water plants were abundant, with Myriophyllum alterniflorum dominant and significant amounts of M. spicatum, Potamogeton praelongus, Chara and Pediastrum. There is no representation of the mosses of Groups F and G during this zone, although there are some pollen indicators (Saxifraga cernua/rivularis, Geum cf. rivale) of other plants of these groups. It is suspected that a diminution of downwash from the surrounding slopes, rather than a real disappearance of the nioss communities, is the explanation for this observation. By zone Bl^lS/l-e Juniperus and tree Betula species have arrived in the area, giving the aspect of 'park tundra' to the landscape. The grassland has become both reduced in area and impoverished in species. At firt Juniperus scrub is dominant ^ith a few tree birches intermixed and a small amount of Empetrum heath, but soon tree birches predominate, presumably competitively eliminating the Juniperus. The lake flora here undergoes a considerable change connected with the gradual lessening of the water depth. Chara dominates during this shallow water phase,

40 380 J. A. WEBB AND P. D. MOORE replacing M. alternifiorum. Equisetum, Typha angustifolia, Carex rostrata and Menyanthes presumably form the vanguard of an advancing mat of fen vegetation. The increase in Eilipendula during this zone is most probably connected with the advance of this vegetation rather than any climatic change. Blackpool Moss The discussion which follows is summarized in Table 3. At this site it is much more difficult to relate macrofossil evidence to microfossil evidence than at Beanrig Moss. At Blackpool Moss the two sorts of evidence come from separate cores (H Table 3. Summary of the vegetational changes during the Late Devensian at Blackpool Moss Assemblage zones, subzones and their dominant pollen taxa BPM-d Juniperus BPM-C3 Grammedi. Artemisia jfuniperus BPM-C2 Artemisia-Betula nana BPM-c, Betula nana-cruciferae- Saxifraga oppositifolia- Artemisia BPM-b Oxyria Cjramineaejfuniperus-Helianthemum BPM-a^ ^Mni/)erMs-Gramineae BPM-a, Juniperus-Filipendula ' Rumex Inferred vegetation Extensive juniper scrub with scattered tree birches. Bare ground communities restricted Bare ground communities dominant. A mozaic of: (i) Artemisia norvegica and associates in wind-exposed areas; (ii) Salix herbacea and associates in areas of long snow lie Poorly-Bowering juniper in a few sheltered areas Dry, open grassland with sparse juniper. Increase in amount of bare. disturbed-ground vegetation Juniper scrub expands coverage, but grasslands and heaths still important Wet, tall meadows with stands of willow. Juniper on drier ground with some tree birch and open short-turf grassland. Some dwarf-shrub heaths for pollen, I and X for macrofossils). For this reason it is not possible to say exactly in which pollen zone a certain macrofossil occurred, and only rough approximation can be achieved. The record from the centre of the basin (cores H and I ) shows the basal clay to be devoid of macrofossils and of any microfossils except a few derived, pre- Quaternary spores. It is thus interpreted as having been laid down rather soon after the deglaciation of the area, before vegetation had arrived to stabilize the surrounding slopes during the interstadial. It is possible that there was a depositional break between the basal clay and the overlying detritus mud, when a period of erosion had removed some of the evidence. The pollen diagram would appear to support this theory, as a short distance above the basal clay, the first countable level indicates that there was a well-developed vegetation cover which, it is surmised, would have taken some time to establish. The first zone is interpreted as indicating the presence of Jfuniperus scrub with a small amount of tree birch, marshy areas with tree willows and damp-ground, tall-herb societies

41 Vegetational history of the Whitlaw Mosses 381 (Group H). The last mentioned are rather well represented with Trollius, Succisa, Urtica-type and Swertia perennis, recorded at this site but not at Beanrig. Swertia perennis is a species of wet, grassy places in the subalpine zone of Europe and has several Late Weichselian records, mostly from Zone III or Zone IV sediments (e.g. Berglund, 1966). The dry, disturbed ground community (D) has representatives in zone BPM-a, and at this site the definition of the community has been improved with the recognition of Artemisia type-e {A. cf. campestris) and Artemisia types B and C {A. cf. maritima). A greater degree of resolution here makes interpretation of the vegetation more difficult, because although Artemisia species are generally ones of open disturbed ground, A. campestris occurs in dry open grassland and thus it may indicate a community rather intermediate between C and D (see Appendix for morphological details). The amounts of Empetrum, Dryas and Betula nana-type can be regarded as indicative of the importance of Group E. The occurrence of many cold-tolerant taxa, e.g. Saxifraga oppositifolia, Silene acaulis/nutans, Lychnis viscariajalpina, cf. Astragalus alpinus and Saussurea alpina is in accord with the very small amounts of tree birch indicated. In subzone BPM-ag Jfuniperus scrub increases its cover and this expansion is correlated with the one recorded from the interstadial sediments of Beanrig (see Table 4 for a correlation of zones at Beanrig Moss with zones at Blackpool Moss). In the sediments of Blackpool Moss the pollen peak is much smaller than at Beanrig, but it is difficult to believe that this means a great deal in terms of the density oi Jfuniperus scrub around the two sites. The fact that Blackpool Moss has a large basin with a bigger catchment, is likely to be the reason why the Jfuniperus pollen peak is smaller and the pollen curve is generally 'smoother' than at Beanrig. The high values for Helianthemum which accompany the Jfuniperus expansion at Beanrig are not apparent at Blackpool, 2 % being the maximum recorded at this time. Not until BPM-b, when Jfuniperus is declining, does Helianthemum become abundant with values up to 5 % of total pollen, indicating its prominence in the grasslands on a scale which approaches that recorded at Beanrig. Although Helianthemum grasslands must have occupied a significant area during BPM-b, it also appears to have been a time when the vegetation cover was becoming increasingly fragmented and the soil disturbed. This is indicated by the higher values for the Group D members Oxyria-type and Cruciferae, and the presence of cf. Echium and Polygonum aviculare. In the stretch of detritus mud just below the upper clay, the macrofossil record shows the consistent presence of Tortella fragilis and Polytrichum sect, juniperina. As at Beanrig Moss the detritus mud below the upper clay is the last sediment in which pollen of Gypsophila fastigiata/repens is recorded. Zone BPM-c (encompassing the whole of the upper clay layer) bears a marked resemblance in terms of pollen and macrofossil content to BRM-c from Beanrig. The whole of zone BPM-c is dominated by Artemisia type-a {A. cf. norvegica) and there are maximum quantities of Cruciferae and Saxifraga oppositifolia in the first subzone. The differences are in the relative amounts of certain pollen types. BPM-c has much smaller percentages of Artemisia type-a than does BRM-c and also the amounts of Artemisia type-b are lower in the former zone. At Blackpool Moss, h records are confined to BPM-c but this is not the case with BRM-c Moss. Also Hippophae occurs consistently throughout BPM-c, but has

42 382 J. A. WEBB AND P. D. MOORE Table 4. Suggested correlation of pollen assemblage zones BEANRIG MOSS BRM-e (Juniperus - Betula- Empetrum PRM-d (Gramineae -Rumex- Cyperaceae) BRM-C3 (Artemisia-Oxyna- Cyperaceae) BLACKPOOL MOSS BPM-d (Juniperus) BPM-C3 {Gramineae - Artemisia - Juniperus) BRM-C2 {Artemisia- Cerastium (Artemisia -Betula nana \ BRM-C {Oxyria - Artemisia) BPM-C {Betula /7C/*7-Cruciferae- Saxifraga oppositifoua - Artemisia) BPM-b (Helianthemum- Betula- Gramineae) Juniperus -Helianthemum) BRM-b (Helianthemum- Betula Gramineae) (Juniperus - Gramineae) (Betula - Salix - Rumex) BRM-a (Salix- Rumex- Myriophyllum alterniflorum) (Rumex -Juniperus Filipendula) only one record in BRM-c. Persistence of this relatively temperate plant through the stadial is implied. However, in general, the records for Blackpool combine to give the same impression as at Beanrig, i.e. areas with long snow-lie intermixed with areas of wind erosion. Compared with BRM-c, BPM-c has relatively high percentages for jfuniperus. At Beanrig Moss the low values gave rise to the idea that Jfuniperus had disappeared from the area altogether, but the Blackpool Moss data shows that Jfuniperus may have been misrepresented. The larger catchment of Blackpool Moss reveals that it persisted throughout this period, perhaps in sheltered localities from which there was no drainage to Beanrig Moss. An alternative hypothesis is that BPM-c is contaminated with sediment redeposited from the Jfuniperus-rich. zones below it (this would also explain the

43 Vegetational history of the Whitlaw Mosses 383 Hippophae records) but the pollen spectra from BPM-c have such low Eilipendula and Rumex acetosa, that it is felt that redeposition did not occur. Birks (1973a) records that high level 'prostrate' juniper may contribute as little as 5% to the total pollen rain, even though its 'cover abundance' is 50%, so one can make few inferences about the quantities oi Jfuniperus scrub present at this time. It is noted that persistence oi Jfuniperus in the area throughout BPM-c would be in accord with the observation of its very rapid pollen rise at the end of this zone, implying that the plant did not have to re-invade the area from distant refuges. Thejfuniperus rise occurs at levels where a spectacular increase in the pollen concentration is seen (probably due to a combination of reduced sediment accumulation rate and increased pollen productivity by the vegetation). In such a situation it is unlikely that Jfuniperus increased its areal extent at the expense of any other taxa, and more likely that a general increase in fiowering had occurred, with Jfuniperus outstripping the other taxa in this respect. Local and regional comparisons The Whitlaw Mosses lie only 10 5 km to the southwest of Whitrig Bog, a site described by Mitchell (1948) and also investigated by Miss A. P. Connolly (see Connolly, 1957). In the sediments of Late Devensian age at this site the range of macrofossils found is substantially similar to that described here (Miss A. P. Connolly, pers. comm.). For example, both sites have Papaver sect, scapiflora seeds and abundant material of Saxifraga spp., and Salix herbacea in the Loch Lomond stadial (Zone HI) sediments. Donner (1957) and Bartley (1966) refer to some unpublished pollen diagrams from Whitrig Bog which were constructed by Godwin. They report that, in the interstadial (Zone II) sediments, values for trees and shrubs at this site ranged between 25 and 60%, suggesting that areas of 'park-tundra' were present. Donner (1957) notes also that Jfuniperus was rather abundant in the diagrams, especially at the begining of Zone IV. In this last feature, the Whitlaw Mosses are in agreement, but the trees and shrub values in the interstadial at these sites never go above 45%, and the representation of tree birches is so small that a much more open vegetation than park-tundra is suggested. At Corstorphine, to the north, Newey (1970) gives further evidence of very open conditions during the interstadial (Zone II) with tree pollen at less than 15 % of the total. To the southeast, at Longlee Moor, Bartley (1966) has tree birch at less than 10 % and Jfuniperus up to 16 %, indicating a treeless but perhaps not shrubless landscape. However, 60 m lower in altitude at his Bradford Kaims site, Bartley has tree birch pollen reaching 20% of the total pollen, and macroscopic remains of tree birch are found combined with Jfuniperus values of up to 60%. It is felt that this must surely indicate open juniper-birch parkland similar to that postulated for the Whitlaw Mosses. Most authors regard tree birch pollen at 20 % of total pollen as the lowest amount indicative of open birch woods. This is supported by the surface pollen studies of Birks (1973a). However, this does not mean that tree birch is absent if percentages go below this level. For instance. Smith (1970) discussing Singh's diagram from Woodgrange, Co. Down, notes that the total Betula values are very low (less than 10%) yet tree birch fruits are found in deposits of the same age in the same area. Obviously from the Betula curves it is difficult to determine to what degree the landscape of southern Scotland and northern England was wooded, as tree-birch must have here been at its climatic limit and the distinction between the pollen of tree birch and dwarf birch is not always reliable. Very low levels for

44 384 J. A. WEBB AND P. D. MOORE birch in the interstadial are recorded as far south as Beamish, Durham (Turner and Kershaw, 1973) but 29 km to the southeast of this site, at Thorpe Bulmer (Bartley, Chambers and Hart-Jone, 1976) tree-birch values of up to 50% must have come from birch woodland. Blackburn (1952) records open birch woodland from Neasham, a little to the southwest of Thorpe Bulmer. At Neasham birch is recorded as up to 80% of total pollen during the interstadial, but the nonrecognition of jfuniperus pollen, combined with a rather frequent occurrence of macrofossils of this shrub, make it unlikely that birch woodlands at Neasham were any denser than at Thorpe Bulmer. Indeed, the abundance of Helianthemum at Neasham leads Blackburn to argue that the landscape must have remained open throughout the period. Perhaps at Neasham there were Helianthemum-rich grasslands which paralleled the interstadial grasslands at the Whitlaw Mosses. The presence of such calcareous grasslands may be deduced from diagrams of other sites in northeast England, e.g. Seamer Carr and Killerby Carr (in Clark, 1954) and Bradford Kaims (Bartley, 1966). Such Helianthemum-rich grasslands were not uncommon in the interstadial of Ireland, e.g. at Ballydugan, Co. Down (Singh, 1970). Biogeographical and ecological implications of some plant records Certain of the taxa recorded during this study are of especial ecological or biogeographical interest, being today either restricted in their British distribution or absent from the British Isles. The criteria upon which the following identifications have been based are given in the Appendix. Artemisia cf. campestris {type E grains) In Britain this species is restricted to the Breckland heaths of East Anglia on dry, open sandy grassland (A and B types of Watt, 1940). The Breckland is regarded as an area cleared of forest by Neolithic cultures (Godwin, 1944). However, despite this artificial origin, Pigott and Walters (1954) argue persuasively for the persistence of small numbers of the rare plants of the Breckland from the Late-glacial 'steppe-grasslands', through the post-glacial forested period, to the time of clearance. From refuges they say that plants such as A. campestris expanded into the open grassland or semi-ruderal habitats they now occupy. A. campestris is regarded by many authors as having a 'continental' distribution-type. Plants of this type are described as ' most frequent over a large area within central Asia, eastern and central Europe, but which have markedly discontinuous occurrence in western Europe' (Piggott and Walters, 1954). Artemisia campestris has been separated into a number of subspecies (see Tutin et al., ) which have slightly different habitat requirements, e.g. Firbas (1949) mentions that A. campestris ssp. borealis is one which is important in the Arctic tundra. Other subspecies grow in 'steppe relict' situations on calcareous moraine, e.g. in the valley of the Rhone and its affiuents in Valais, also in the Aosta valley of Piemonte (Persson, 1974). The certain presence of Artemisia campestns S.I. in the Late Devensian interstadial, would be strong evidence in favour of both the existence of such steppe grasslands at this time and perhaps also the relict status of Artemisia campestris on the Breckland today. Artemisia cf. maritima s.l. {type B and type C grains) The number of subspecies within this taxon make discussion of the find rather difficult. As in A. campestris s.l. the subspecies differ from one another in ecology Some are confined to saline substrata (e.g. ssp. maritima) while others can exist

45 Vegetational history of the Whitlaw Mosses 385 in non-saline as well as saline areas (e.g. ssp. humifusa). Persson (1974) in his study on the Artemisia maritima complex reported that most are confined to steppes or similar habitats on saline or calcareous substrata, the areas concerned being mostly arid. The presence of A. maritima s.l. during the Late Devensian could be taken as an indication of the saline character of soils in the area, but this is thought unlikely. Other authors, e.g. Bell (1969, 1970), have inferred the existence of saline conditions in the past by the association of several obligate halophile species in the macrofossil remains, but the salt-dependence of many such plant species has been questioned. Persson's (1974) studies on the germination of seedlings of Artemisia maritima showed that they germinate best in the absence of NaCl, and that seedling growth was optimal in a nonsaline medium or salt solutions of very low concentrations. Salt tolerance was acquired with age. In the light of these observations, together with the results of the present study, it is suggested that during Late Devensian, there existed inland, non-haline populations of Artemisia maritima s.l. as had been shown for populations oi Armeria maritima and Plantago maritima (see McVean and Ratcliffe, 1962; Godwin, 1975). Artemisia cf. norvegica (Type A grains) A. norvegica is a species which today has a very disjunct distribution. It occurs in small colonies on the tops of mountains in the Urals, southern Norway and Scotland. The finding of this species in the Late Devensian at the Whitlaw Mosses adds weight to the suggestion that the distribution has (during the post-glacial) undergone a contraction from a much wider distribution during Late-glacial times. High temperature and competition from other species during the early Flandrian would have eliminated the plant from the lowlands in Selkirkshire and Roxburghshire (Borders), but it might have been expected to persist longer in certain high ground stations (e.g. the Moffat hills described by Ratcliffe, 1959) which are famed for their collection of' Late-glacial relict' species. It may be noted that little information can be gained on the ecological requirements of a species when it has such a restricted distribution as A. norvegica, where the individual plants are often surviving in small isolated colonies, under sub-optimal conditions. The species may be absent from suitable sites because of chance examination followed by inability to recolonise from the nearest refugium. Gypsophila fastigiata or G. repens Whichever species is represented at the Whitlaw Mosses, the biogeographical implications of the find are important. G. fastigiata is a very well known example of a 'continental' species. According to Jager (1972) this distribution type is limited by low winter temperature or short length of growing season in the northeast, drought and soil in the southeast, low summer temperature in the northwest and high winter temperature (which favours competing oceanic psammophilous plants) in the west. However, in the specific case of G. fastigiata, as the range is regressive, historical factors probably play a bigger part in the observed pattern than do climatic ones. If the subfossil record does refer to this species, the occurrence would be in accord with the ideas put forward by Coope, Morgan and Osborne (1971). These authors suggest (on the basis of beetle remains) that late in the interstadial the climate may have been moderately continental, with winter temperatures depressed more than summer temperatures below their present values. G. repens is a more southern species than G. fastigiata, occurring on mountains

46 386 J. A. WEBB AND P. D. MOORE in most central European countries, from the Jura, Alps and Carpathians to northwest Spain and central Italy (Tutin et al., ). It is an example of an ' alpine') species in the stricter sense of the term, i.e. it shows no tendency to extend north into the Arctic areas (as do many cold-tolerant, competition-intolerant species). Hedysarum cf. hedysaroides This is a species found only in the mountains of south central Europe, but it has a more continuous distribution in Arctic Russia and the north and central Urals (Tutin et al., ). The other European species oi Hedysarum have more restricted distributions, but in general are found in similar habitats, i.e. mountain meadows, rocks and sunny slopes (Polunin, 1969). It would appear that the open conditions required by Hedysarum species were in existence around the Whitlaw Mosses until the end of the Loch Lomond Stadial. These identifications, and others, present a weight of information pointing to the conclusion that the climate of the late interstadial and stadial (Loch Lomond) at the Whitlaw Mosses was of the continental type. The records of species which are no longer British, combined with the greater similarity of certain of the inferred communities to continental European ones (e.g. the Artemisia norvegica community of BRM-c and BPM-c with the current vegetation of its Trollheimen station, rather than its Scottish site) is a reflecttion of the fact that the two floras (British and European) were, during Late Devensian Late-glacial times, continuous, as the low sea levels would have left a wide land-bridge between the two land masses. The eastern coast of Britain was then presumably much less subject to oceanic influences than it is now. Additional evidence for such a continental climate during the Loch Lomond stadial in eastern Scotland has been provided by Macpherson (1980), who based his conclusions upon sediment texture and lamination in a kettle hole in the Spey Valley, together with a general survey of Artemisia levels in the area. ACKNOWLEDGEMENTS One author (J. A. W.) held an NERC research studentship during the period of this research. REFERENCES ALBERTSON, N. (1950). Das grosse sudliche Alvar der Insel Oland. Eine pflanzensoziologische Ubersicht. Svensk botanisk tidskrift, 44, ANDERSEN, S. T. (1961). Vegetation and its environment in Denmark in the Early Weichselian Glacial (Last Glacial). Danmarks geologiske undersogelse ser II, 75, BARTLEY, D. D. (1966). Pollen analysis of some lake deposits near Bamburgh, Northumberland. New Phytologist, 65, BARTLEY, D. D., CHAMBERS, C. & HART-JONES, B. (1976). The vegetational history of South and East Durham. New Phytologist, 11, BEHRE, K. E. (1967). The Late Glacial and Early Post Glacial history of the vegetation and climate in North-Western Germany. Reviews of Palaeobotany and Palynology, 4, BEIJERINK, W. (1947). Zadenatlas der Nederlandsche Flora. Veenman, Wageningen: BELL, F. G. (1969). The occurrence of southern, steppe and halophyte elements in Weichselian (last glacial) floras from southern Britain. New Phytologist, 68, BELL, E. G. (1970). Late Pleistocene floras from Earith, Huntingdonshire. Philosophic Transactions of the Royal Society of London, B, 258, BENNIE, J. (1894a). Arctic plants in the old lake deposits of Scotland. Annals of Scottish Natural History, 9,

47 Vegetational history of the Whitlaw Mosses 387 BENNIE, J. (1894b). On the occurrence of peat with Arctic plants in boulder clay at Faskine, near Airdrie, Lanarkshire. Tranasactions of the Geological Society of Glasgow, 10, BERGLUND, B. E. (1966). Late Quaternary vegetation in Easter Blekinge, South-eastern Sweden. A pollen analytical study. I. Late Glacial time. Opera botanica a Societate botanica lundensi, 12, BERGLUND, B. E. & DIGERFELDT, G. (1970). A palaeoecological study ofthe Late Glacial lake at Torreberga, Scania, South Sweden. Oikos, 21, BERTSCH, K. (1941). 'Fruchte und Samen. Handbucher der Praktischen Vorgeschichtesforschung\ Ferdinand Enke, Stuttgart. BEUG, H-J. (1957). Untersuchungen zur spatglazialen und friihpostglazialen Floren- und Vegetationsgeschichte einiger Mittelgebirge. Flora, Jena, 145, BIRKS, H. J. B. (1973a). Past and Present Vegetation ofthe Isle of Skye. A Palaeoecological Study. Cambridge University Press, Cambridge. BIRKS, H. J. B. (1973b). Modern pollen rain studies in some arctic and alpine environments. In: Quaternary Plant Ecology (Ed. by H. J. B. Birks & R. G. West), pp Blackwell, Oxford. BLACKBURN, K. B. (1952). The dating of a deposit containing an elk skeleton found at Neasham, near Darlington, Co. Durham. New Phytologist, 51, BONNY, A. P. (1972). A method for determining absolute pollen frequencies in lake sediments. New Phytologist, 71, 393-^05. BONNY, A. P. (1978). The effect of pollen recruitment processes on pollen distribution over the sediment surfaces of a small lake in Cumbria. Journal of Ecology, 66, BURROWS, C. J. (1974). Plant macrofossils from Late Devensian deposits at Nant Ffrancon, Caernarvonshire. New Phytologist, 73, CHANDA, S. (1962). On the pollen morphology of some Scandinavian Caryophyllaceae. Grana Palynologica, 3(3), CLAPHAM, A. R., TUTIN, T. G. & WARBURG, E. F. (1962). Flora of the British Isles, 2nd edn. Cambridge University Press, Cambridge. CLARK, J. G. D. (1954). Excavations at Star Carr. Cambridge University Press, Cambridge. CONNOLLY, A. P. (1957). The occurreiice of seeds of Papaver sect. Scapiflora in a Scottish Late Glacial site. Verojfentlichungen Geobotanischen Instituts, Zurich, 34, CooPE, G. R., MORGAN, A. & OSBORNE, P. J. (1971). Fossil Coleoptera as indicators of climatic fluctuations during the Last Glaciation in Britain. Palaeogeography, Palaeoclimatology, Palaeoecology, 10, DAHL, E. (1951). On the relation between summer temperature and the distribution of alpine vascular plants in the lowlands of Fennoscandia. Oikos, 3, DANIELS, R. E. (1972). A preliminary survey of Beanrig Moss, a fen in South Scotland. Transactions of the Botanical Society of Edinburgh, 42, DICKSON, C. A., DICKSON, J. H. & MITCHELL, G. F. (1970). The Late Weichselian flora ofthe Isle of Man. Philosophic Transactions of the Royal Society of London, B, 258, DICKSON, J. H. (1973). Bryophytes of the Pleistocene. The British Record and its Chorological and Ecological Implications. Cambridge University Press, Cambridge. DixoN, H. N. (1924). The Student's Handbook of British Mosses, 3rd edn. Sumfield & Day, Eastbourne. DoNNER, J. J. (1957). The geology and vegetation of Late-glacial retreat stages in Scotland. Transactions of the Royal Society of Edinburgh, 63, Du RiETZ, G. E. (1923). Studien iiber die Helianthemum oelandicum - Assoziation auf Oland. Svensk botanisk tidskrift, 17, ERDTMAN, G. (1944). Sadesslagens pollenmorfologi. Summary in English: Pollen morphology ofthe cereals. With notes on pollen morphology in Triticale. Svensk botanisk tidskrift, 38, ERDTMAN, G. (1956). 'LO-analysis' and 'Welcker's rule', a centenary Svensk botanisk tidskrift, 50, 1-7. ERDTMAN, G. (1960). The acetolysis method. Svensk botanisk tidskrift, 54, ERDTMAN, G. (1969). Handbook of Palynology. Morphology - Taxonomy ~ Ecology. Munksgaard, Copenhagen. ERDTMAN, G., BERGLUND, B. & PRAGLOWSKI, J. (1961). An Introduction to a Scandinavian Pollen Flora. Almqvist & Wiksells, Uppsala. ERDTMAN, G., PRAGLOWSKI, J. & NILSSON, S. (1963). 'An Introduction to a Scandinavian Pollen Flora II. Almqvist & Wiksells, Uppsala. EAEGRI, K. & IVERSEN, J. (1974). Textbook of Pollen Analysis, 3rd edn, by K. Faegri. Blackwell, Oxford. EERGUSON, I. K. & WEBB, D. A. (1970). Pollen morphology in the genus Saxifraga and its taxonomic significance. Journal of the Linnaean Society of London, {Botany), 63, EiRBAS, F. (1949). 'Spat- und Nacheiszeitliche Waldgeschichte Mitteleuropas nordlich der Alpen'. Fischer, Jena. EREDSKILD, B. (1967). Palaeobotanical investigations at Sermermiut, Jakobshavn, West Greenland. Meddelelser om Gronland, 178(4), 1-54., O. (1950) The snow-bed vegetation in the surroundings of Lake Tornetrask, Swedish Lapland. Svensk botanisk tidskrift, 44(2),

48 388 J. A. WEBB AND P. D. MOORE GJAEROVOLL, O. (1963). Survival of plants on nunataks in Norway during the Pleistocene glaciation. In' North Atlantic Biota and their History {Ed.hy A. Love &D. Love), pp Academic Press, London GODWIN, H. (1944). Age and origin of the Breckland heaths of East Anglia. Nature, 154, 6-8. GODWIN, H. (1975). History of the British Flora, 2nd edn. Cambridge University Press, Cambridge. GRAY, J. M. & LOWE, J. J. (1977). The Scottish Lateglacial environment: a synthesis. In: Studies in the Scottish Lateglacial Environment (Ed. by J. M. Gray and J. J. Lowe), pp Pergamon Press Oxford. GROVES, J. & BULLOCK-WEBSTER, G. R. (1920). 'The British Charophyta. vol. i. Nitelleae, vol. ii Chareae' The Ray Society, London. HAMMEN, T. VAN DER (1951). Late Glacial flora and periglacial pnenomena in the Netherlands. Leidsche geologische mededlingen, 17, HoLMEN, K. (1959). The distribution of bryophytes in Denmark. Botanisk tidsskrift, 55, IVERSEN, J. (1954). The Late Glacial flora of Denmark and its relation to climate and soil. Danmarksgeologiske Undersogelse (II), 80, JAGER, E. J. (1972). Comments on the history and ecology of continental European plants. In Taxonomy, Phytogeography and Evolution (Ed. by D. H. Valentine), pp Academic Press, London. JARAI-KOMLODI, M. (1966). Etudes palynologiques des couches de la Derniere epoque Glaciaire (Brorup, Pleniglaciaire) de la Grande Plaine Hongroise. Pollen et Spores 8(3), JESSEN, K. & FARRINGTON, A. (1938). The bogs at Ballybetagh, near Dublin, with remarks on Late Glacial conditions in Ireland. Proceedings of the Royal Irish Academy, 44B, 10, JowsEY, P. C. (1966). An improved peat sampler. New Phytologist, 65, KATZ, N. J., KATZ, S. V. & KIPIANI, M. G. (1965). Atlas and Keys of Fruits and Seeds Occurring in the Quaternary Deposits of the U.S.S.R. Nauka, Moscow. KELLER, B. A. (1927). Distribution of Vegetation on the Plains of European Russia. Journa/ of Ecology, 15, LAMBERT, C. A. PEARSON, R. G. & SPARKS, B. W. (1963). A Elora and Fauna from Late Pleistocene deposits at Sidgwick Avenue, Cambridge. Proceedings of the Linnaean Society of London, 174, LANG, G. (1951). Nachweiss von Ephedra im Siidwestdeutschen Spatglaziale. Naturwissenschaften 38, 334-^335. LANG, G. (1952). Spateiszeitliche Pflanzenreste in Siidwestdeutschland. Beitrdge zur naturkundlichen Forschung in Siidwestdeutschland 11, LOVE, D. (1963). Dispersal and Survival of Plants. In: North Atlantic Biota and their History, (Ed. by A. Love & D. Love). Pergamon Press, Oxford. MACPHERSON, J. B. (1980) Environmental change during the Loch Lomond Stadial: evidence from a site in the Upper Spey Valley, Scotland. In: Studies in the Lateglacial of North-west Europe (Ed. by J. J. Lowe, J. M. Gray & J. E. Robinson), pp Pergamon Press, Oxford. MANGERUD, J., ANDERSEN, S. T., BERGLUND, B. E. & DONNER, J. J. (1974^). Quaternary stratigraphy of Norden, a proposal for terminology and classification. Boreas, 3, MCNEILL, J. & BASSETT, I. J. (1974). Pollen morphology and the infrageneric classification of Minuartia (Caryophyllaceae). Canadian Journal of Botany, 52, MCVEAN, D. N. (1955). Notes on the Vegetation of Iceland. Transactions of the Botanical Society of Edinburgh, 36, MCVEAN, D. N. & RATCLIFFE, D. A. (1962). Plant Communities of the Scottish Highlands. Monographs of the Nature Conservancy 1, H.M.S.O., London. MEUSEL, H. (1940). Die Grasheiden Mitteleuropas Versuch einer vergleichend-pflanzengeographischen Gliederung. Botanisches Archiv, Berlin, 41, MITCHELL, G. F. (1948). Late Glacial deposits in Berwickshire. New Phytologist, 47, MITCHELL, G. F. (1952). Late Glacial deposits at Garscadden Mains, near Glasgow. New Phytologist, 50, MITCHELL, G. F. (1953). Further identifications of macroscopic plant fossils from Irish Quaternary deposits, especially from a Late Glacial deposit at Mapastown, Co. Louth. Proceedings of the Royal Irish Academy, B52, MOORE, P. D. (1970). Studies in the vegetational history of Mid-Wales. II. The late-glacial period in Cardiganshire. New Phytologist, 69, MOORE, P. D. & WEBB, J. A. (1978). An Illustrated Guide to Pollen Analysis. Hodder & Stoughton, London. MOSIMANN, J. E. (1965). Statistical methods for the pollen analyst. Multinomial and negative multinomial techniques. In: Handbook of Palaeontological Techniques (Ed. by B. G. Kummel & D. M. Raup). pp Freeman, San Francisco. NEWEY, W. W. (1970). Pollen analysis of Late Weichselian deposits at Corstorphine, Edinburgh, Phytologist, 69, PENNINGTON, W. (1980). Modern pollen samples from West Greenland and the interpretation of pollen data from the British late-glacial (Late Devensian). New Phytologist, 84, PERSSON, K. (1974). Biosystematic studies in the Artemisia maritima complex in Europe. Opera botantcao Societate botanica lundensi, 35, 1-88.

49 Vegetational history of the Whitlaw Mosses 389 PiGGOTT, C. D. (1956). The vegetation of Upper Teesdale in the North Pennines. Journal of Ecology, 44, PiGGOTT, C. D. & WALTERS, S. M. (1954). On the interpretation of the discontinuous distributions shown by certain British species of open habitats. Journal of Ecology, 42, PoU'NiN, O. (1969). Flowers of Europe. Oxford University Press. PROCTOR, M. C. F. & LAMBERT, C. A. (1961). Pollen from recent Helianthemum communities. New Phytologist, 60, PUNT, W. & NIENHUIS, W. (1976). Gentianaceae. In: The North-west European Pollen Flora (Ed. by W. Punt), vol. I, RAGG, J. M. (1960). The Soils Around Kelso and Lauder. Memoirs of the Soil Survey of Great Britain, H.M.S.O., London. RAGHUVANSHI, S. S. & JosHi, S. (1967). Anethumgraveolens : Polyploidy and pollen variability. Flora, Jena, 157B, RALSKA-JASIEWICZOWA, M. (1972). Remarks on the Late Glacial and Holocene history of vegetation in the Eastern part of the Carpathian Mountains. Bericht der deutschen botanischen Gesellschaft, 85(1-4) RATCLIFFE, D. A. (1959). The Mountain Plants of the Moffat Hills. Transactions and Proceedings of the Botanical Society of Edinburgh, 37, RAUSCH, K-A. (1975). Untersuchungen zur spat und nacheiszeitlichen Vegetationsgeschichte im Gebiet des ehemaligen Inn-Chiemseegletschers. Flora Jena, 164, ROBERTSON, D. (1881). On the Post-Tertiary beds of Gravel Park, Greenock, Transactions of the Geological Society of Glasgow, 7, RYMER, L. (1973). Modern pollen-rain studies in Iceland. New Phytologist, 72, SINGH, G. (1970). Late Glacial vegetational history of Lecale, Co. Down. Proceedings of the Royal Irish Academy, 69B, SissoNS, J. B. (1967). The Evolution of Scotland's Scenery. Oliver & Boyd, Edinburgh. SissoNS, J. B. (1974). The Quaternary in Scotland; a review. Scottish Journal of Geology, 10(4), SMITH, A. G. (1970). Late-glacial and post-glacial vegetational and climatic history of Ireland; a review. Irish Geographical Studies, Queen's University of Belfast. SMITH, A. J. E. (1978). The Moss Flora of Britain and Ireland. Cambridge University Press, Cambridge. STERNER, R. (1938). Flora der Insel Oland. Acta phytogeographica suecica, 9, TEERI, J. A. (1973). Polar desert adaptions of a high Arctic plant species. Science, New York, 179, TURNER, J. & KERSHAW, A. P. (1973). A Late- and Post-glacial pollen diagram from Cranberry Bog, near Beamish, Co. Durham. New Phytologist, 72, TUTIN, T. G. et al. (eds) ( ). Flora Europea vols. i-v. Cambridge University Press, Cambridge. VASARI, Y. & VASARI, A. (1968). Late- and Post-glacial macrophytic vegetation in the lochs of Northern Scotland. Acta botanica fennica, 80, VERBECK-REUVERS, A. A. M. L.(1980). Saxifragaceae. In: The North-west European Pollen Flora (Ed. by W. Punt & G. C. S. Clarke), vol. 2, pp Elsevier, Amsterdam. WATT, A. S. (1940). Studies on the ecology of Breckland. IV. The grass heath. Journal of Ecology, 28, WASYLIKOWA, K. (1964). Vegetation and climate of the Late-glacial in Central Poland based on investigations made at Witow, near Leczycy. Biuletyn peryglacjalny, Lodz, 13, WEBB, J. A. (1977). Studies on the Late-Devensian vegetation of the Whitlaw Mosses, south-east Scotland. Unpublished Ph.D. thesis. University of London. WEST, R. G. (1964). Inter-relations of ecology and Quaternary palaeohotany. Journal of Ecology 52 (Jubilee Symposium Supplement), WILSON, D. G. (1973). Notable plant records from the Cromer Forest Bed Series. New Phytologist, 72, APPENDIX Pollen and macrofossil identifications Full descriptions of all taxa identified are to be found in Webb (1977). Only taxa of especial interest are described here. s.l. Grains were placed in this type before it was found to be possible to distinguish the genera Arenaria and Minuartia into a separate group {Arenaria-type ^ s). The present type is a group (defined to a certain extent on negative criteria)

50 39O J. A. WEBB AND P. D. MOORE containing grains with cylindrical columellae arranged in a regular manner between the pori (columellae never arranged in a reticulate pattern as in Silene dioica, or in an irregular pattern as in Cerastium-type). Examination of type slides at a later date in this study, showed that the following species could be grouped under the above description: Arenaria leptoclados, A. serpyllifolia, A. ciliata, A. norvegica, Honkenya peploides, Minuartia hybrida, M. rubella, M. stricta, M. verna, Cherleria sedoides. Lychnis viscaria, L. alpina and Silene acaulis. Arenaria-fy/)^ s.s. Grains placed in this type had the spaces between the pori well-filled with columellae which were arranged in a regular manner. Perforations were always distinct, their density always being greater than or equal to the density of the columellae. The width of the perforations was less than or equal to that of the columellae. Most of the fossil grains had perforations approximately equal in width to the columellae, a condition which was observed in grains on type slides of Minuartia verna, M. hybrida, M. stricta, M. rubella an'd Cherleria sedoides. Only a few fossil grains had perforations smaller than the width of the columellae. This character was observed in grains on type slides of Arenaria serpyllifolia and A. leptoclados. The fact that other fossil grains appeared to be intermediate with regard to this character was the reason for not separating 'Arenaria-type s.s.' still further. The scanning electron micrographs of Minuartia species produced by McNeil and Bassett (1974) show the extent of variation in perforation-density within this genus. Arenaria ciliata s.l., Arenaria norvegica and Honkenya peploides are not included in this type as their pollen grains have very coarse columellae and numerous tiny perforations which make them distinctive. None of the fossil grains resembled these species morphologically. Arenaria-type s.s. is recognized only from Blackpool Moss because the typeslides needed for comparisons were not available at the time of the analysis of Beanrig Moss. Records of pollen identifications ofthe genera Arenaria and Minuartia are rather rare. Birks (1973a) describes an 'Arenaria-type\ whilst Mitchell (1953) records 'Minuartia' and Berglund (1966) finds 'Arenaria sp.', 'Minuartia cf. biflora' and 'M. cf. peploides'. Cerastium-type Grains placed under this heading had columellae which were irregular in thickness and spacing. The columellae often appeared clustered around the pori, and many of the columellae in the centre of the mesoporium were of the hanging type. Perforations were distinct, even in bright field illumination, and were numerous (always more abundant than the columellae). Many fossil grains were assigned to this type. On examination of type slides, all Cerastium species, most Stellaria species, Myosoton aquaticum, Moenchia erecta and Holosteum umbellatuin had grains of this type. Dianthus sp. Six pollen grains were identified to a species of Dianthus because of their small number of pori (12 or less), their coarse columellae (that were irregular in shape and distribution but which sometimes occurred in a reticulate pattern) and their small, distinct, sparse perforations and prominent echinae. Erom LO-analysis,

51 Vegetational history of the Whitlaw Mosses 391 it appeared that the columellae were markedly narrower at their bases than at their tops. Often a reticulate pattern could be perceived within the focal plane at the level of the bases but not within that at the level of the tops of the columellae. All species of Dianthus examined (Z). armeria, D. caryophyllus, D. deltoides, D. arenarius, D. carthusianorum, D. gratianopolitanus) had pollen grains of this type. The grains in Saponaria, Tunica saxifraga and Vaccaria pyramidata were found to be similar but are discounted on morphological grounds. Gypsophila repens/fastigiata In the sediments of both Beanrig Moss and Blackpool Moss were found pollen grains of a member of the Caryophyllaceae which were very distinctive and which are described in Faegri and Iversen (1974) and Chanda (1962) as belonging to the genus Gypsophila. Five grains were observed at Beanrig Moss and seven at Blackpool Moss. They varied only slightly in size, being about 35 jivn. The number of pori was commonly 12, although one grain was observed with 13 and two with 11. The general exine structure was of a fairly common type, being tectate perforate with the width of the perforations less than or equal to the width of the columellae. The perforations and columellae were of similar density, and the columellae were cylindrical and regularly packed in the mesoporium. The most distinctive feature of these grains was the very wide annulus which surrounded each of the pori. This was especially noticeable because of the rather small size of the grains. Annuli from 15 (ivcv up to 2-5 iin\ were noted. Only G. fastigiata and G. repens had annuli of the required thickness and otherwise closely resembled the fossil grains. Gypsophila pollen grains have not been recorded from any British deposit (see Godwin, 1975) and there are no native Gypsophila species. In pollen diagrams from European deposits Gypsophila grains are recorded from sediments of Late-glacial (Weichselian) age. Very often authors simply list the finds under the heading ' Gypsophilla' and it is here assumed that this refers to the species with wide annuli as it is rather difficult to separate the species with narrow annuli (G. muralis, G. paniculata) from some other Caryophyllaceae. Amongst papers dealing with the Late Weichselian where simply ' Gypsophila' is recorded is Rausch (1975). Iversen (1954), Berglund (1966) and Ralska-Jasiewiczowa (1972) go further and record 'G. fastigiata' or 'G. fastgiata-type\ whereas Beug (1957), Andersen (1961) and Behre (1967) record ' Gypsophila fastigiata or repens\ Finds of pollen grains from sediments formed earlier than the Late Weichselian appear to be limited to those of Jari-Kolmlodi (1965) who reports 'Gypsophila' from the Brorup interstadial. Macrofossil finds, for example, those of Lang (1952) of G. repens seeds in Germany, and of Wasylikowa (1964) of G. fastigiata seeds in Poland, show that both these species were able to exploit the conditions that existed during Late-glacial times. cf. Lychnis viscaria/alpina Grains tentatively identified to either of these species were medium sized (approximately 30 [im) with numerous slender, cylindrical columellae which were evenly distributed between the pori. Perforations were also numerous and only Slightly smaller in diameter (under phase-contrast) than the columellae. The perforations were much less distinct than those in the species of Minuartia (grains of which were otherwise similar to the fossil grains). It was often the case that perforations could not be detected using bright field illumination, but became clear

52 392 J. A. WEBB AND P. D. MOORE under phase-contrast. Grains closely similar to the fossil ones were seen on type slides of Lychnis viscaria and L. alpina. Differentiation between these species was not possible. Five grains were found, all from Blackpool Moss. Seeds of Lychnis viscaria and L. alpina have been recorded from the Late Devensian of the Isle of Man by Dickson, Dickson and Mitchell (1970). Silene cf. acaulis/nutans Grains placed under this heading had columellae which were much coarser (in relation to grain-size) than in Minuartia species or Lychnis species. The columellae were either arranged in a reticulate pattern or packed fairly regularly in the area between the pori (this'last was the commonest situation). Perforations were present and were observed under phase-contrast to be both much smaller in diameter than the columellae and much less abundant than the columellae. The grains were medium sized (about 32 ju,m) and always had more than 13 pori. Grains on type slides of Silene acaulis were indistinguishable from the fossil grains, but it was observed that grains of S. nutans could also look very similar to them. Of the other species of Silene with tectate-perforate grains, i.e. 5. otites, S. vulgaris, S. gallica and S. conica, only the first two species were available for comparison. In S. otites the grains were too small and pori too close together, and in S. vulgaris the pori were too few in number, thus the fossil grains could be equated with neither of these species. The taxon Silene acaulis/nutans was recognized only during the counting of the slides from Blackpool Moss, when 11 grains were identified. A re-examination of some of the grains placed under Arenaria-type s.l. (from Beanrig Moss) revealed two more grains referable to Silene acaulis/nutans. Several authors recognize a ' Silene-type', e.g. H. H. and H. J. H. Birks (in Godwin, 1975) and H. J. B. Birks (1973) has gone as far as to recognize Silene acaulis separately from other Silene species in the Late Devensian sediments of the Isle of Skye. Silene vulgaris- One grain from Beanrig Moss was identified to this type as it was tectateperforate with a low number of pori, having very coarse columellae and perforations sparse compared to the abundance of the columellae. It was closely comparable to grains seen on type slides of <S. vulgaris and S. martima. It is not known how many of the European Silene species may come under this type. Artemisia {Fig. 12) Most of the grains placed in this genus were trizonocolporate, tectate-echinate (with echinae 1-5 fim high) and with exine thickest in the centre of the mesocolpium. However, (as is discussed below) the morphology within Artemisia is rather variable, so that this general description is not necessarily true for every fossil grain that was seen. The fossil pollen grains encountered at Beanrig Moss and Blackpool Moss appeared to fall into several types, each with a more or less distinct suite ot morphological characteristics. These types were scored separately and the positions of the grains were recorded so that they could be re-examined at a later date. Grains which could not be placed in any of the recognized types were recorded under ' Artemisia indeterminate' along with those Artemisia grains which were too fragmented, degraded, eroded or obscured to permit critical observation of their morphology.

53 Vegetational history of the Whitlaw Mosses 393 The morphological criteria upon which the fossil grains were segregated into types were as follows. (1) The degree of prominence of the echinae (or conversely, the. degree of smoothness of the tectum) assessed by an optical section of the grain under magnification of x 1000 and surface views under magnifications of x 400 and X 1000 (using phase-contrast). (2) The comparative density of the echinae in surface view and optical section. Two subjective categories were recognized: (a)'sparse in comparison to the distribution of the columellae; (b) ' dense' in comparison to the density of the columellae. Observation of this feature was always carried out under magnification x 1000 and phase-contrast. (3) The density, arrangement and shape of the columellae as revealed by LOanalysis (Erdtman, 1956) and by examination under phase-contrast. The subjective categories recognized for density were ' closely packed' or ' spaced' and for arrangement were ' regular' or ' irregular' whilst those for shape were 'circular in cross-section'. (4) The degree to which the pori were defined and their apparent shape. Size variation was observed to bear little relation to the types distinguished. The Artemisia types scored separately during the pollen counts were as follows. Type-A. Grains placed in this category had thin, unbranched cylindrical, densely-packed columellae and distinct, sparse echinae. In optical section the grain shape varied from elliptic to circular. Some grains had very indistinct endopori (generally the more elliptic of the grains) whereas others had had distinct, circular endopori (the more circular of the grains). Upon examination of the type slides, grains with columellae of similar fineness and density and with echinae as sparse as type-a were found in A. pontica, A. norvegica and A. borealis (although in this last only a few grains conformed). Amongst the fossil grains in type-a, the more elliptic with the indistinct endopori were found to agree most with A. norvegica type material from Norway, although they were all smaller than the Norwegian grains. A. borealis was nearer the size of the fossil grains, but a large percentage of the grains on the type slide showed irregular grouping (or branching) of the columellae (see type-d). The more circular fossil grains with well-defined endopori most resembled A. pontica. although it must be said that in some of the fossil grains the pori were m.ore clearly defined than the best examples of A. pontica. Type-B. Grains placed in this category had columellae which were coarse and sparse in relation to the size of the grain. These coarse columellae were noncylindrical, and in LO-analysis presented a very irregular cross-sectional outline. In optical sections it was observed that this was the result of each columella branching at half to one-third of its length and meeting the tectum as a group of tiny rods. Even when no branching could be observed, the columellae were very thick and 'spaced-out'. Such thick, irregularly-shaped columellae were most noticeable in the middle of the mesocolpium, thinner and more cylindrical columellae being apparent towards the edges of the colpi and in the apocolpia. In grains with such columellae, the echinae were observed to be minute and very densely packed. Some grains appeared completely smooth (even phase-contrast did not show up any trace of echinae). When minute echinae were present, they were in surface view either as dense or more dense than the columellae. ANP 91

54 394 J. A. WEBB AND P. D. MOORE Type-B grains usually had approximately circular endopori, overlain by ectocolpi which tended to curve in a rather characteristic manner (see Eig. 12) although this feature did not appear in every grain placed in type-b on the basis of characters of columellae and echinae. Upon examination of type slides it was apparent that branching, coarse columellae which were irregular in cross-section occurred to different degrees in several species. In A. maritima spp. maritima, however, such columellae occurred in a high percentage of the grains, these grains also having minute and dense (or undetectable) echinae and distinctive circular endopori. A. austraica also had some grains conforming to type-b as described above, but the agreement was here less good. Type-C. Grains placed in this category had fine, cylindrical, dense, unbranched columellae and either no echinae or minute, dense echinae. The apertures were similar to those of type-b in that the endopori were well defined and approximately circular. Examination of type slides revealed that a few type-c grains were present on the slides of A. maritima ssp. maritima that exhibited typical type-b grains. A. maritima ssp. suffruticosa had type-c grains present in the majority, with only a few type-b grains. In addition grains that could be assigned to type-c were also detected on slides of A. vallesiaca and A. austraica. Type-C grains were not distinguished at the time of the Beanrig Moss counts, so it is to be noted that their lack from the diagram does not necessarily imply their absence from the site. Type-D. Grains placed in this category had both coarse columellae with irregular cross-section and distinct, sparse echinae. Relatively few fossil grains fell into this class. It has not so far been possible to match these grains to any of the species examined. Grains of A. arctica and A. laciniata were noted to possess distinct echinae and some coarse, irregular columellae, but in other respects did not resemble the fossil grains exactly. Type-E. Grains placed in this category were circular in equatorial-view optical section, with fine, densely-packed cylindrical columellae that were neither as dense in comparison to the grain size as in types B or C, nor as sparse as in Type-A. The feature in which they were distinct from the other Artemisia types was the poor development of the pori. Each porus appeared no more than an interruption of the endocolpus in the equatorial region of the grain. If the grains were fully expanded, a thin, equatorially elongated rupture indicated the position of the porus (see Fig. 12). These fossil grains appeared indistinguishable from grains on type slides of British material of A. campestris. Ten grains were found at Blackpool Moss. Type-E grains were not recognized at the time of the Beanrig Moss counts. Type-E. Two grains were found (one in Beanrig Moss, one in Blackpool Moss) which appeared so unusual as to not be immediately recognizable as belonging to the genus Artemisia. They appeared completely smooth, with an undulating tectum which gave the grains a verrucate appearance under x 400 magnification. Under x 1000 magnification and phase-contrast it could be seen that they had a mixture of coarse, irregular (i.e. branched) columellae and cylindrical unbranched columellae. On one of them, minute echinae could be discerned under phase-

55 Vegetational history of the Whitlaw Mosses 395 contrast. Both were circular in equatorial-view optical section and had fairly well defined pori. Such grains as these were observed in type material from Germany oi A. salina. Willd., a taxon which is now included within A. maritima s.l. This material, however, had other grains with aperture and size aberrances as well as the characteristic exine structures described above. It is thus not clear whether the grains on the type slide represent the normal state for A. salina or are just a feature of the particular plant collected. Size and aperture disturbances are found in the pollen grains of hybrids or individuals that may be genetically abnormal in some other way, e.g. polyploids (see Erdtman, 1944, 1969; Raghuvanshi and Joshi, 1967). It is thought likely that the unusual exine characteristics described above could also be a reflection of such genetic disturbances. Examination of more pollen from within A. maritima s.l., especially from known hybrids, is obviously necessary here. Artemisia indeterminate Grains placed in this class (in addition to those which were too broken, degraded or obscured for critical investigation) were ones which did not fit into any of the types A to F. Some grains placed in the indeterminate group closely resembled grains on type slides of A. vulgaris, but they could not definitely be distinguished from grains of A. absinthium, A. rupestris, A. atrata, A. laciniata, A. scoparia and some grains of A. maritima and A. campestris. A. vulgaris seemed to vary considerably in size, degree of prominence of the echinae and structure of the columellae, both within and between collections. A few of the grains even exhibited irregular columellae similar to the ones seen in A. maritima, although never in conjuction with the dense, minute echinae seen in that species. Artemisia sect, dracunculus {Fig. 10) A small Artemisia capitulum (which lacked florets) was washed from a clay at 3-20 to 3 30 m, Beanrig Moss. This clay was otherwise very poor in macrofossils. The capitulum was 3-5 mm in length (including the peduncle) with three outer bracts which were mostly herbaceous and three inner bracts (phyllaries) which had wide, scarious margins. The capitulum was compared with material from British Artemisia species, but no convincing match could be made. It was sent to Dr K. Persson of the University of Goteborg for examination. He is of the opinion that the size of the capitulum, combined with the regular arrangement of the bracts when viewed from below bring it nearest to section dracunculus. Tutin et al. (Vol. IV, 1976) list nine species within this group: A. dracunculus, A. glauca, A. trautvetterana, A. salsoides, A. tschernieviana, A. commutata, A. bargusinensis, A. campestris and A. scoparia. A. campestris is a rather variable species, being represented by six subspecies. The capitulum was then compared with such material of the above species as was available to the authors. A. scoparia had capitula which are too small for it to be identified with the fossil and none of the subspecies of ^. campestris which were examined (i.e. ssp. alpina, ssp. botanica, spp. campestris and ssp. maritima) had bracts which were quite the same as in the fossil. A. dracunculus had peduncles which were much longer than that of the fossil. Specific identification, therefore, remains uncertain.

56 396 J. A. WEBB AND P. D. MOORE cf. Swertia perennis Two pollen grains at 6-46 m, Blackpool Moss, were trizonocolporate, faintly reticulate-striate, with well marked endopori and had a thick exine (> 2/tm) containing densely-packed, cylindrical columellae. These columellae were united only at the extreme apex. The striate pattern was more conspicous near the colpi, and the reticulate pattern was more conspicious in the middle of the niesocolpia. Swedish Swertia perennis material produced pollen grains which closely resembled the fossil ones. However, it was observed that the type grains had a more pronounced reticulum than did the fossil grains and definitive identification must await the examination of more material of Swertia and other Gentianaceae. Punt and Nienhuis (1976) note that the grains of Swertia closely resemble those of Gentianella, but the fossil grains were too small for G. amarella (which was also recorded). Swertia perennis pollen has occasional records in European sediments and there have been finds by Andersen (1961), Ralska-Jasiewiczowa (1972), Berglund (1966) and Beug (1957). In Britain a Swertia perennis seed was found in Pastonian/early Beestonian deposits by Wilson (1973) but there are no records of the species from later sediments. Astragalus danicxxs-type Twenty-six grains at Beanrig Moss and three grains at Blackpool Moss assigned to this type were medium in size (about 37 (im in length) trizono-colporate with pori indistinct, and suprareticulate-foveolate with usually ^15 pits across each mesocolpium in the equatorial region (see Eaegri and Iversen, 1974). The lumina became smaller and the muri wider towards the apocolpia, so that these last appeared either tectate with scattered pits or tectate and completely smooth. Grains from type material of Astragalus danicus and Oxytropis campestris both agreed well with the fossil grains and it was not possible to say to which of these species they may have belonged. It was noted that the other members of Astragalus and Oxytropis which were examined (i.e. O. halleri, A. arenarius, A. frigidus, A. glycyphyllos) although varying in morphology, were all distinctly different from O. campestris and A. danicus. Hedysarum cf. hedysaroides Eive grains at Beanrig Moss and 13 grains at Blackpool Moss conformed to this general description: trizonocolpate, finely reticulate, rectangular-obtuse in equatorial-view optical section, size ranging between 24 and 32 fim. The grains agree well with type material of Hedysarum hedysaroides, but the possibility of other Hedysarum species must be considered. cf. Medicago falcata A grain found at level 2-26 m Beanrig Moss appeared closely similar to grains on a type slide of Medicago falcata. It was 38-3 x 40/^m in size, trizonocolpate with a very slight deflection of the colpus at the equator indicating the possible presence of a porus. The surface was alomst smooth, phase contrast showing up minute scabrae. The columellae were distinct, fine, cylindrical and arranged in an even carpet all over the grain. Pollen of Medicago does not seem to have been recorded from Late-glacial or post-glacial deposits. However, there is a report of a seed of 'Medicago sp.' by

57 Vegetational history of the Whitlaw Mosses 397 Lambert, Pearson and Sparks. (1963) from deposits formed during the onset of Devensian glacial conditions. Saxifraga cernua/rivularis Three grains at Beanrig Moss and two grains at Blackpool Moss had the distinctive sculpturing type of these two species. The grains were trizono-colpate (or variously pantocolpate) circular or elliptic in equatorial-view optical section, in size between 25 and 30 fim, and either tectate or semitectate. The sculpturing pattern was composed of indistinct striae which were not immediately detectable under normal (bright field) illumination, but were clear under phase-contrast. It should be noted that under normal illumination the grains resembled those of S. granulata (see below). The ridges (muri) of the striate sculpturing were much broader than the gaps (lumina). The columellae were coarse, in thickness equalling the width of the muri and in arrangement appearing in only one row under each murus. Verbeck-Reuvers (1980) claims that S. rivularis is not straite, but this does not conform with our type material. Of the rest of the genus Saxifraga, according to Ferguson and Webb (1970) besides S. cernua and S. rivularis, only 5. tridactylites has the combination of very faint striate patterning with broad muri. Observation of type slides of S. tridactylites showed that the columellae were too fine and the grains altogether too small for it to be equated with the fossil grains. The S. rivularis/cernua pollen type has been recorded from Late Devensian deposits before, e.g. Bartley (1966) as 'S. cernua'. Saxifraga granulata- Many grains of this type were found at both sites. The type here is defined as having grains which were trizonocolpate (or variously pantocolpate), tectate perforate and scabrate with minute echinae. The columellae were fairly coarse and disposed in an even carpet under the tectum. Occasionally grains with operculate colpi were observed. In these cases the sculpture on the operculum was the same as that in the mesocolpium. The pantocolpate grains were always much larger than the trizonocolpate ones. Although size varied greatly, the pantocolpate grains were nearly always over 38 /im in diameter. It is thought that the majority of the grains found (especially the larger, operculate ones) belong to S. granulata itself, but as grains of S. cespitosa, S. hirculus, S. hypnoides and S. rosacea also conformed to the description above, specific identification was not possible. Saxifraga oppositifolia Many grains were identified to this species. The grains closely resemble those of S. aizoides and some confusion is possible (see Ferguson and Webb, 1970; Verbeck-Reuvers, 1980). In general the polar axis: equatorial axis ratio of grains IS greater in S. oppositifolia, but no numerical analysis was attempted. Tortella fragilis {Hook & Wils.) Limpr. {Fig. 11) Many fragments of a very distinctive moss leaf type were found at all of the three sites investigated. The fragments usually consisted of a section of a long, thin leaf which had a very strong nerve and a lamina composed of isodiametric, highly papillose cells. It was not until the finding of fragments with intact apices and other fragments with complete leaf bases that it became obvious that Tortellafragilis was