Summary Radiocarbon dates for a number of pollen analytic features marking important vegetational changes in the Post‐glacial of the British Isles are plotted in two figures (Figs. 2 and 3, summarized in Fig. 4). Despite the limitations of the radiocarbon method it becomes clear, where sufficient dates are available, that most of the vegetational developments of the earlier part of the Post‐glacial are diachronous. Some of these changes have been used as pollen zone boundaries. The elm decline appears synchronous, however, within the limits of the methods, and the final pine decline in Ireland, which is shown to be older than supposed by Jessen (1949), appears to be one of the least diachronous of the horizons examined. Marked differences in the dates of similar vegetational changes within a small area, and between upland and lowland, are pointed out.

SUMMARYTbe establisbment and expansion of alder [Alnus glutinosa (L.) Gaertner] in Britain between approx. 8000 and 5000 years ago is discussed in relation to cbanges of climate and sea-level, and to buman influences.Detailed pollen analyses of Mesolitbic layers at Newferry, Co. Antrim are presented. Evidence from tbis and otber sites suggest widespread disturbance of forest cover wbich, by locally reducing competition, (cf. McVean, 1956) appears to bave been one of tbe factors in tbe establisbment of alder.Estuarine babitats are suggested as baving importance in tbe spread of alder but tbe onset of climatic wetness was probably not a key factor (as bas often bitberto been supposed) otber tban in tbe sense of being permissive.Key words: Newferry, Boreal-Atlantic transition, alder, pollen analysis, radiocarbon dating. INTRODUCTORY REVIEWThis paper sets out to re-examine some of the pollen analytic and stratigraphic evidence for vegetational and environmental change at the classical horizon known as the Boreal-Atlantic transition. The use of these terms has been abandoned by many recent authors, and for quite good reasons. Nevertheless, they still serve as a convenient framework in which to enclose the rise of the pollen curve of alder [Alnus glutinosa (L.) Gaertner] which is a prominent feature of all Flandrian pollen diagrams of sufficient age.The names ' Boreal' and ' Atlantic' are derived from the work of the famous Scandinavian bog geologists. Axel Blytt and Rutger Sernander (for references and some summary in English see Fries, 1965a, b). Working in late Victorian and Edwardian times they interpreted the presence of trees in peat bogs to imply a dry climate in the period they called 'Boreal' and the absence of trees in the superincumbent layer to indicate a wet climate: the 'Atlantic' period. (As is well known, the sequence was considered to have been repeated, giving names, again with climatic implications to the Sub-boreal and Sub-atlantic periods.) Even in 1909, however, we find another Scandinavian worker, Gunnar Andersson putting considerable obstacles in the way of the simple interpretation of tree stutnp layers in peat as indicative of climatic dryness.Despite objections such as these the Blytt-Sernander terms, together with their climatic implications, became transferred to the pollen zones that were subsequently defined both on the continent and in Britain. Andersson's doubts have been raised again, however, by the most recent study of tree-layers in peat in Britain. Birks (1975) concludes that little regional climatic significance can be assumed from the occurrence of pine stumps in Scottish bogs, and that they cannot be taken as evidence in support of dry Boreal and Sub-boreal periods. Despite this, there is evidence of Boreal dryness from other sources (see below).

Objective To review the practice in two hospitals with further samples despite providing two consecutive clear ones. At Hospital B, 24 (24%) patients failed to diCering protocols in the timing of seminal analysis after vasectomy. provide samples; 10 (13%) patients had persistent spermatozoa at 6 months and live spermatozoa were Patients and methods The results from 245 vasectomies carried out at Hospital A, where semen was assessed detected in one patient's samples. All eventually produced clear samples, with none requiring exploration. 3 months after vasectomy, were reviewed and compared with those from 100 consecutive vasectomies After changing the protocol, 87 vasectomies were performed, with 18 (21%) patients failing to provide at Hospital B, where semen was assessed 6 months after vasectomy. The results of seminal analysis at samples; seven (10%) of the samples collected showed occasional nonmotile spermatozoa at 6 months in Hospital A were also audited after changing to the 6-month protocol. The patients' preferences for the either the first, second or both samples, with all samples clear by 8 months after vasectomy. timing of seminal analysis were also obtained. Results Of the 245 patients at Hospital A, 58 (24%)Conclusions The complete disappearance of spermatozoa after vasectomy takes longer than is generally believed failed to provide samples, leaving 187 (76%) for evaluation; 528 samples were examined (mean 2.8 and we therefore suggest that given adequate counselling, seminal analysis 6 months after vasectomy is per patient, range 1-13). The first sample was positive in 36 (19.3%) and the second positive in 10 (5.3%), cost-eCective and in the patient's interest.

Detailed boring records and surface levels, combined with knowledge of the rate of extension of organic deposits in the lake basin (Part 1), allow the production of a computer-generated contour map and isometric drawings of the microtopography of the area around the Star Carr site of Clark (1954) (figs 1 and 2). The site was at the mouth of a shallow gully on the southern face of a hillock of glacial till which could be reached from the higher ground to the N over dry ground. The hillock extended into the lake basin as a low peninsula ending in a spit, at the entrance to its relatively narrow outflow channel. The occupation area was at a point where the open water most closely approached the shore and extended from the marginal wetland on to the dry slopes of the hillock.Pollen and lithological analysis, combined with extensive C14 dating, is described at four closely spaced points along a section through the basin deposits close to the Star Carr site. Dated sequences of local vegetation development are established. The results are used to reconstruct pictorially the environmental changes through a period of occupation contemporaneous with, and presumably an extension of, the occupation of the Star Carr site (fig. 9). The dry ground supported birch wood throughout, but natural successional changes in the wetland, on a nominal timescale, were as follows:(a) At 9800 BP the open water of the lake lapped the shore save for a narrow zone of reeds, sedges and water plants.(b) By 9650 BP immediately before the occupation, reedswamp dominated by the great reed (Phragmites) had extended well into the basin. There was a narrow drier zone at the landward side of the reedswamp with abundant ferns enclosing a damper patch with fen plants.(c) At the time of the occupation, around 9600 BP, the inshore reedswamp had largely been replaced by fen dominated by the saw sedge (Cladium). The marginal environment, where artefacts were found, was still dominated by ferns but a wood layer occupied the former damp fen area, presumably having been deliberately emplaced to consolidate the ground. Cladium fen and fringing reedswamp formed an extensive tract to the E of the occupation area behind the spit mentioned above, and probably also to the W.(d) By 9300 BP (on the nominal timescale used for the reconstruction) the occupation was over and the wood layer and an associated ‘brown layer’ were covered by Cladium deposits on which willows were now growing.Attention is drawn to the need for detailed work on the taphonomy of artefacts as a component of any further excavation in the organic deposits of the Vale of Pickering.

Sixteen sites in and around a small upland bog in South Wales were investigated by means of pollen analysis and radiocarbon dating. Most of the sites have ombrogenous (blanket) peat overlying a thin basal mor with abundant charcoal. A Devensian Late-glacial basin filled with muds and reedswamp deposits is shown to underlie the blanket peat in part of the area. It is concluded that the outlet of the basin was probably blocked by the development of ombrogenous peat, perhaps around 6500 years BP (though not closely dated), which spread across the basin and later up its western shore. The pollen diagrams are divided into a series of pollen assemblage zones. The zone boundaries appear synchronous within the limits of the methods. Hazel played an important role in the woodland vegetation of the pre-peat mineral soils. This woodland had generally been replaced by heath and blanket peat by about 6000 years BP. Nevertheless, some woodland apparently persisted locally in areas where peat or mor accumulation had not yet begun. Alder appears to have been established in the basin area by ca . 7000 years BP and to have spread more widely some 500—1000 years later, possibly taking advantage of environmental damage caused by Mesolithic man, evidence of whose occupation is found in the area. It is concluded that Mesolithic man was probably responsible for making a small clearing in the woodland at ca . 8000 years BP when the first mor deposit began to accumulate. Heath vegetation first came into existence at about this time and there is circumstantial evidence of maintenance by burning. Heath conditions lasted in some areas until ca . 5500 years BP and on the more permeable soils podsolization took place. It is argued that the accumulation of relatively impermeable mor soils under heath was a major factor in the initiation of ombrogenous peat growth. This most generally began in the period ca . 5500-5800 years BP though it was both earlier ( ca . 7600 years BP) and later ( ca . 4000 years BP) in some areas. A comparison is made of the behaviour of certain pollen curves at the major sites in which it is found that sites with common features fall into spatially coherent groups. It is concluded, therefore, that the pollen diagrams often reflect vegetational changes taking place in relatively small areas. A reconstruction of the vegetational changes in the 4000 years after ca . 8000 years BP is made by means of a series of maps. The classical elm decline of the Atlantic-Sub-boreal transition ( ca . 5000-5500 years BP) is variably represented and there follows a series of three other declines or minima dated to ca . 4600 years BP, ca . 4000 years BP and ca . 2850 years BP (though again with some possible variability). The Bronze Age appears to have been a time of major human impacts on the local vegetation with some woodland regeneration taking place in the earlier Iron Age before a renewed period of clearance that persisted through Romano-British times.