On the Vegetation of Four Durham Coal-Measure Fells: I

On the Vegetation of Four Durham Coal-Measure Fells: I. General Description of the Area and Its Vegetation Author(s): Harold Jeffreys Source: Journal of Ecology, Vol. 4, No. 3/4 (Dec., 1916), pp. 174-195 Published by: British Ecological Society Stable URL: http://www.jstor.org/stable/2255630 . Accessed: 25/06/2014 09:31

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ON THE VEGETATION OF FOUR DURHAM COAL-MEASURE FELLS

I. GENERAL DESCRIPTION OF THE AREA AND ITS VEGETATION

BY HAROLD JEFFREYS

(WithPlate XI and threeFigures in theText)

INTRODUCTION

The term"fell" is extensivelyused in the Northof Englandto denote a tractof elevatedcountry in a moreor lessuncultivated condition. Well- knownexamples are Scafell,Cross Fell, Bow Fell and WiddybankFell. In thewest of Durham, where the underlying rocks are mainlythe coarse sand- stonesof the Bernician and MillstoneGrit series, the ground on them is mostly coveredwith thickpeat, and the principaldominant plants are Calluna vulgaris,Eriophorum vaginatum, and Sphagnumspp. (mainly S. cymbifolium)'. The vegetationtherefore belongs to the moorformation. In the east of the county,however, the coal measuresoutcrop, and manychanges in the environmentare associatedwith the geologicalchange. The rainfalldimin- ishes,the soils are mostlysand (oftenvery fine) and clay,and the elevation is lower. Most of the westof the countyis over1000 feet in height,while in the coal measurearea a hillof over800 feetis a rarity. Peat is seldom ornever formed, save in exceptionalcircumstances, and onsome of the steeper slopeseven humusis not to be found. The nativevegetation is divided mainlybetween the heath, marsh, and neutralgrassland formations, although the last is largelydue to humaninterference, which is in mostlocalities of considerableimportance. The soil of N.E. Durhamis readilycultivated, and the arable area considerablyexceeds that under pasture. Natural woodlandis nearlyabsent, and plantationsusually line the steepbanks of streams,as theseare almostimpossible to utiliseotherwise. The area (Fig. 20) is drainedby the RiversTyne and Wear,and their tributaries.The only affluent of the Tyne that we needconsider is theTeam, a dirtystream about 13 milesin length,which rises near AnnfieldPlain, 1 Lewis, F. J., "Geographical distributionof vegetation in the basins of the Eden, Tees, Wear and Tyne." Geogr.Journ. 28, 1904, pp. 313-331.

This content downloaded from 188.72.126.25 on Wed, 25 Jun 2014 09:31:36 AM All use subject to JSTOR Terms and Conditions H. JEFFREYS 175 flowseast for8 miles,and turnsnorthwards at Birtley,falling into the Tyne near Gateshead. From Birtlevto Gateshead it followsthe old valley of the Wear, known as the "Great Durham Wash." Of the tributariesof the Wear, the most importantfor our purposeare the Cong Burn and the South Burn, whichenter the main streamrespectively at the northend of Chester- le-Streetand a mile south of that town.

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The Team flowsin a wide and low valley, and on the sides of it rise the steep RavensworthHills and the SheriffHill range. The ground remains low betweenBirtley and Chester-le-Street;to the south-westof this is the elevated ground of the Waldridge and Edmondsley neighbourhood. Geo- logicallythis is probablycontinuous with the RavensworthHills. The fourfells to be describedin this paper are WaldridgeFell, Beamish Fell, BirtleyFell, and TinklerFell. The annual rainfallin the districtis usually about 28 inches, but its seasonal distributionis very variable. No Britishvegetation seems to have been describedthat bears any close resemblanceto that of this area. That of the Pennines is widelydifferent, and the moors of North-East Yorkshire', although on Jurassic rocks, resemble the Pennine moors more than the coal-measure heaths. The heaths of the New Forest are related to it, and some featuresof the coal- measureheaths show an affinitywith the sandy areas of the Breck Country2. The present paper consists of a descriptiveaccount of the vegetation; it is proposed to deal subsequentlywith experimentalwork that has been carriedout on certainpoints connected with it. The maps have been taken fromthe 6-inch ordnance survey charts, and the details filledin from a triangulation. The general map of the district(Fig. 20) is derived from the half-inchBartholomew map, sheet 2.

GENERAL DESCRIPTION OF THE FELLS CONSIDERED Waldridge Fell, where most of the work in this paper has been done, lies about two and a half miles south-westof Chester-le-Street,and is a roughlyrectangular area approximatelyhalf a square mile in extent. To the northof the village is a furthertract of waste ground,disconnected from the main Fell but ecologicallya part of it. The Fell is extremelyirregular in its verticalsection, ranging in heightfrom 427 feetto 150 feet,while the hills are thirteenin number. The south-eastside of the Fell is bounded principallyby the South Burn, and the north-westside by the Cong Burn. These are both small streams,of a yellow colour owing to the oxidation of ferroussulphate in the water, this being itselfan oxidation product of the iron pyritesin the coal of neighbouringpits. The sides of these streams away from the Fell are mostly covered with plantations, excepting the portion of the South Burn to the south of the ChesterMoor road. Here the Fell extends east of the stream to the top of a steep hill covered with bracken,while the moisterground in the valleyis spontaneousand apparently natural woodland, of Betula alba on the rightbank and Alnus rotundifolia

1 Blgee, P., "Eastern moorlandsof Yorkshire." This JOURNAL, 2, 1914, p. 1. 2 Parrow, E. P., "On the ecology of the vegetation of Breckland." T-hisJOURNAL, 8, 1915, p. 211.

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on the left. The rightbank of the Cong Burn is an almost precipitousslope all the way, and fromthe point where the stream entersthe Fell to the railwaybridge it is covered with an oak-hazel wood. A sparse alder wood lines both banks of the streammuch lower down, just beforeit leaves theFell. Many small streamsrise withinthe area. The whole of the south-west side is drained by that marked 1 in Fig. 21, althoughthis itselfleaves the Fell immediatelyafter its source in Bog 7. Stream 2 is a tributaryof it, whilethose marked3 and 4 end blindlyin a depressioncontaining numerous small Juncuseffusus bogs. Streams5, 6 and 7 are fed by the large Wanister bog (Bog 11), while 8, 9 and 10 also fall into the South Burn. A few small intermittentstreams enter the Cong. Of all the fourteenstreams in Fig. 21, however,only Nos. 1, 5 and 10 are permanent. The othersall become dry in August. Most of the bogs also are not permanentlywet, the exceptions being Nos. 4, 7 and 11. In addition the duck pond 5 never becomes dry, and Bog 13 veryrarely does so. Both of these drain into the Wanisterbog, thoughby no very definitechannel. Of the hills withinthe area, the highestis Hill 10, overlookingthe village. The most strikingin appearance, however,is the Wanisterhill (Hill 2), on account of its sharp rise fromthe low-lyingground where the Wanisterbog lies. Hills 6 and 7 are mere rubbishheaps, 8 is an old air shaft,and 11 is a pit heap. A bare and precipitousslope overhangsthe valley that contains Bog. 7. The generaltopography consists of a gradual but irregularrise fromthe South Burn and Stream 1 up to the ridge where Hills 10 and 12 stand. Round these is a plateau, with a steep slope to the north. The detached portionis likewisea plateau, sloping very rapidlyto the Cong Burn, whose valley is indeed a ravine. A furtherinteresting area is a disused pasture north-eastof this, between the plantationand the burn. Pasturingis not extensiveon the Fell, only a few ponies being fed, while rabbits occur only on Hills 1 and 3, and in the pasture just mentioned. On these two hills they are scarce, and apparentlyhave little effecton the vegetation. They may have been more plentifulformerly, as the steep slope opposite Hill 13 is knownas "Rabbit Banks." The sandy areas are a large tongue extendingfrom Hill 3 nearly to the rows of houses surroundingPond 5, a smaller patch near the east corner, and the detachedpart. The rest is mainlyclay, with varyingquantities of sand. Human interferenceis in evidence in several ways. Two waggon-ways intersectthe Fell, but their effecton the vegetationseems very local. The heaps of shale fromthe collierieshave a highlycharacteristic vegetation, as have also the Smithydenequarries near the Edmondsley road. The most interestingeffects due to human agency are, however,the constructionof footpathsand burning. The formerappears to introduce two ecological

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This content downloaded from 188.72.126.25 on Wed, 25 Jun 2014 09:31:36 AM All use subject to JSTOR Terms and Conditions H. JEFFREYS 179 factors,namely, mechanical wear and water content. All of these effects on the environmentmust be regardedas in a sense biotic,although indirect in some cases. I have no evidence that any part of the Fell has ever been cultivated. The followingplants attain dominance on various parts of Waldridge Fell. Dry grassland:-Festuca rubra, Agrostis vulgaris. Heath:-Pteris aquilina, Calluna vulgaris (with Empetrumnigrum), Vaccinium myrtillus, Ulex europaeus,Deschampsia flexuosa, Holcus mollis,Nardus stricta. Inter- mediate:-Holcus lanatus, Molinia coerulea, Carex goodenowii. Marsh: Juncusglaucus, J. effusus,J. acutiflorus,Epilobium hirsutum, Glyceriafluitans, Sparganiun ramosum,Eleocharis palustris,Alopecurus geniculatus, Agrostis alba. Woodland:-Quercus sessiliflora,Corylus avellana, Alnus rotundifolia, Qrataegusmonogyna, Betula alba, Salix cinerea. Ruderal or transient: Senecio viscosus,Poa annua, Rumex acetosella. Beamish Fell is at the most southerlypoint of the course of the Team, which flowsround three sides of it. The Team at this point is a pebbly streamabout fouryards across. The Fell rises steeplyfrom it on all sides. Although not at present interferedwith by man, it has probably been a plantation in quite recent times, as young trees of the Great Maple (Acer pseudoplatanus)occur frequently,and this tree is not indigenous. The area is marked as a plantationin the Ordnance Survey Map of 1850 under'the name of OusbroughWood. The southernslope is indeed a youngplantation now, and the whole area is marked as woodland in Bartholomew'smap (sheet 2). To the northis an older plantation,mainly of Great Maple and Quercussessiliflora. There is littlevariety in the vegetation,the only domi- nants being Pteris aquilina, DeschampsiafJexuosa, Holcus mollis,Betula alba. The soil is verysandy, except on parts of the southernslope, whereit is clay. There is no pasturage, and at presentlittle human interference.Rabbits occur, especially near the top. Birtley Fell lies about a mile and a half north-eastof the town of Birtley,and is the southernextremity of the SheriffHill ridge. It is a long and narrowstrip of elevated ground,running roughly north and south. In contourit is comparativelyregular, being merelya fairlysteady slope up to the most northerlypoint, where Shadon's Hill (487 feet) stands. There are no natural streams,but several ditches have been cut for drainage, apparentlyto adapt the area for pasture. Much of it is now enclosedand cultivated,but of the part that remainscommon land little has ever been ploughed. Three air-shaftsdisfigure the Fell, and thereare onlythree ponds, all artificialand quite uninterestingduckponds. Two considerable bogs exist. A featurethat has not, I believe, been explained,and that does not occur on any of the other fells,is the occurrenceof many meres near the highestpoint. These are small depressions,varying in size. The largest are about three yards across and a yard deep, while the smaller are only

This content downloaded from 188.72.126.25 on Wed, 25 Jun 2014 09:31:36 AM All use subject to JSTOR Terms and Conditions 180 The Vegetationof four Durham Coal-Measure Fells about one-thirdthe size each way. Some are permanentlyfilled with water, but most dry up in summer. The sides are very steep, and the water is peaty. They are probably to be attributed to very old pitfalls. The subsoil is stiffboulder-clay in the northand coarse sand in the south. The area is much used forhorse pasture,but rabbits are absent. There are fewfootpaths, but the Fell is used as a golfcourse, and muchturfing takes place in order to repair the greens,and one long slope is regularlyrolled. A first-classroad runs along the east side, and a branchof it crossesthe Fell, but is fenced. Burningoccurs, but is not so extensiveas at Waldridge. Associations dominated by the followingplants occur on Birtley Fell: Agrostisvulgaris, Calluna vulgaris, Ulex europaeus,Nardus stricta,Juncus squarrosus,Molinia coerulea,Alopecurus geniculatus. Tinkler Fell occupies the highest point of the ridge of the Ravens- worthHills. In shape it is roughlysquare, risingto the highestpoint in the centre,which attains over 700 feet. Close to this hill is the only pond on the Fell. There are a few intermittentstreams. Along the south-eastern edge was a pine plantationtill recently,but this has now been felled. The Ravensworthwoods are on the northernside, with a local area of heath of somewhatdifferent type fromthe main Fell. Rabbits are plentifulon this part, but rare on the main portion. A few hawthornhedges cross the Fell, giving evidence of formerpasturage. In 1850, accordingto the ordnance survey made about that date, the north-easternhalf of the Fell was under pasture, but little differencecan now be detected between the two halves, except in the ribbed appearance of the ground of the part that has been ploughed. Communitiesdominated by the followingspecies occur:-Agrostis vulgaris, Calluna vulgaris,Holcus mollis,Nardus stricta,Juncus effusus.

II. DESCRIPTIONS OF THE ASSOCIATIONS (1) Dry grassland (Agrostetum vulgaris) is developedat the extremeeast cornerof WaldridgeFell, and also dominatesthe pasture that overhangsthis corner,just outside the Fell proper. It surroundsPond 5, extendingbetween the gardens of the houses and the edge of the pond. Owing to the fowlskept by the miners,manuring at this point is intense. At some points on the south-westernedge it appears between the railings and the nearest path. Part of an area on the northernside, formerlyen- closed as a pasture,but now disused,is coveredwith it, and also the disused pasture adjacent to the detached portion. It occupies in addition other pastures round the Fell. It seems probable that pasturage does actually encouragethe developmentof this association,particularly on dry ground. The same association occurs on the drierparts of BirtleyFell, and also on a verydry and sunnybank at the northside of a pond on,Tinkler Fell.

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The compositionof the associationis as follows'. (1) At Waldridge:- Agrostisvulgaris cd Rubus idaeus o Plantago lanceolata o Festuca rubra cd Conopodiumdenudatum o Rumex acetosella o Ranunculus repens f Galium saxatile o R. acetosa 0 Stellaria media o G. verum f Luzula campestris f Cerastiumtriviale o Hypochaerisradicata o Festuca ovina a Polygala vulgaris f Hieraciumpilosella I Poa annua o Trifoliumrepens a Cnicus arvensis f P. pratensis a T. minus r C. lanceolatus o Dactylis glomerata f T. hybridum r Achillea millefolium f Holcus lanatus f T. procumbens r Crepisvirens r H. mollis o Medicagolupulina o Leontodon autumnalis o Anthoxanthumodoratum a Potentillafragariastrum f Campanula rotundifolia o Cynosuruscristatus f P. erecta o Calluna vulgaris vr Equisetum arvense r (2) At Birtley:- Agrostis vulgaris d Genista anglica r Prunella vulgaris o Sagina procumbens o Rubus fruticosusagg. o Plantago major f Polygala vulgaris I Leontodon autumnalis a P. lanceolata f Trifoliumminus o Bellis perennis a Rumex acetosella a T. repens f Taraxacum officinale f Luzula campestris a T. pratense r Campanula rQtundifolia f Triodia decumbens o Lotus corniculatus o (3) On TinklerFell: Agrostisvulgaris d Rumex acetosella o Nardus stricta f Trifoliumminus r Luzula campestris sd Aira praecox f T. repens vr Holcus mollis o Poa pratensis o Galium saxatile f Festuca ovina f Cynosuruscristatus I B3ellisperennis vr F. rubra o

Along the intermittentwater-courses on BirtleyFell Agrostisgrowth is stimulated; Poa annua and Holcus mollisare mixed with it. This association is clearlyseparated fromthe fringingNardetum, which then passes into Calluna and Whin (Ulex). In places this damp Agrostetumis invaded by Juncus squarrosus. Agrostisis dominant on the greater part of Shadon's Hill. The soil is pure finedry sand, with a verythin layer of humus. (2) Bracken association (Pteridetum aquilinae) is at present completelydominant over all the area on Waldridge where the subsoil is dry sand; it does not attain perfectdominance except in these conditions, althoughin some places on sandy clay it may be seen in competitionwith Ulex and Calluna, and even with Nardus. It is not developed on Birtley Fell or TinklerFell, and at Beamish it is in competitionwith Deschampsia flexuosa. The species associated with the brackenare very few: whereit is growingmost thickly there are none at all, but whereit becomes somewhat thinner Deschampsiaflexuosa, Vaccinium myrtillus,or Holcus mollis may become subdominant. It occursfurther in several of the plantations,especially in some of those on the northside of the Cong valley. From these it is capable of spreadinginto the surroundingland.

1 The following contractions are used in these lists: a, abundant; cd, codominant; d, dominant; f, frequent; 1, local; la, Id, etc., locally abundant, locally dominant, etc.; O, occasional; r, rare; sd, subdominant; vr, very rare.

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Both of the methods of propagation of bracken (by rhizomesand by spores) are of great importancein enabling it to establish itself,but each has its limitations. In general we are safe in saying that nearly all of the new bracken stems in a continuous Pteridetum are from the rhizomes, whereaswhere there is a brackenpatch separated by several yards fromall other areas covered with the same plant the original colonisation of the outlier was due to spores. This association will be consideredin greater detail later. (3) The Heather association (Callunetum vulgaris). At present the amount of pure Callunetumat Waldridge (Fig. 22) is not great. There is a small patch of it beside Stream 5, and it occurs irregularlybetween the Cong and the main road to Chester-le-Street,on a steep slope facing north. The northernslope of Hill 10 also is nearly pure Callunetum. The greater part of the plateau containingHills 9, 10 and 12 was probably originallyCallunetum, and heatheris now dominantover a very large part of it, but it appears to be degenerating,partly to bracken,partly to Nardus, and partlyto Molinia. At Beamish heatheris never dominant. At Birtley it occurson a great part of the Fell, chieflynear the northend; it is never- theless degeneratingto Ulex and Nardus, and the plants are neververy tall. This association reaches its greatestdevelopment on TinklerFell, covering morethan half of it withwell-grown bushes. A peculiarityof Calluna is the persistenceof its bark afterthe refuseof the plant has been buried below humus. The gradual raisingof the level of the groundby depositionof vegetable mattercauses considerablequantities of the dead refuse of the dominantplants to be buried in humus, though most of the materialultimately gets washed away by rain. Most of what remainsrots and helps to make additional humus. It is a remarkablefact that unless Calluna has been actually burntto charcoal,the bark remainsin the soil in a recognisablecondition long afterthe woodypart has disappeared. I have never succeeded in identifyingit, however,at a greaterdepth than fourinches. This persistenceof the refuse(even thoughit is not nearlyso well preservedas it sometimesis in peat) makes it possible to forma very usefulestimate of the formerextent of the Callunetumon the Fells, which at Waldridge and Birtley was much greaterthan it now is. I have thus found Calluna refusein the followingplaces at Waldridge:-on Hill 1; on the southernslope of Hill 2; near the path just below Pond 5; and on several places on Hill 13. It has not been foundnear Bogs 1, 2 and 3, whereNar- detum now occurs. Calluna must then have formerlygrown over most of the sandy area that is now coveredwith bracken, and as Calluna now occupies all the remainingdry and sandy parts except the small area near the east corner,we may concludethat nearlyall the dry sandy portionof Waldridge Fell is now or has been formerlyCalluna heath, and much of it has since degeneratedto Pteridetum. At Birtley also Calluna was formerlymore.

This content downloaded from 188.72.126.25 on Wed, 25 Jun 2014 09:31:36 AM All use subject to JSTOR Terms and Conditions 184 The Vegetationof four Durham Coal-Measure Fells extensivethan it is now. Explanationsof this degenerationwill be given later. On the elevatedpart of WaldridgeFell we may see Callunaareas sur- roundedby Nardetum,in whichthe Pterisis confinedto the Callunetum, noneof it appearingin theNardetum. Sometimes,but notalways, there is a zoneat theedge where the Callunetum is pure(i.e. devoidof Pteris). There are severalobviously possible explanations of this fact. One is thatwe are here dealingwith an incompletezonation in the orderBracken, Calluna, Nardus,in whichthe factortending to cause the dominanceof brackenis notpresent to suchan extentas to producethe full effect. Another is that the Calluna-Nardusseparation occurred originally, and thatfor some reason Pteriswas able to colonisethe Callunnaareas, but not the Nardetum. It willbe shownlater that the latter suggestion is sufficientto accountfor the factnoted, although it maynot be theonly factor operating. Callunaon thesehills produces a purplish-brownstain in the sand to a depthvarying from 15 to 30 centimetres,but rarelyseems to cementthe grainsso as to producea pan, as has been recordedfrom other localities. The writerhas observeda ratherhard purplish pan severalinches deep in a partof the Ulexarea on BirtleyFell, but thisdoes not seem to havQbeen sufficientto preventthe Ulexfrom ousting the Callunaafter the pan was formed. The compositionof the Callunetum is as follows:- Waldridge Birtley TinklerFell Ulex europaeus 0 - - Potentilla erecta o a r Rosa canina o Crataegusmonogyna o Hieraciumumbellatum - - vr Leontodon autumnalis - - r Vacciniummyrtillus f sd Erica cinerea f a E. tetralix f Empetrumnigrum a Luzula multiflora - f Nardus stricta f a f to cd Agrostisvulgaris f Holcus mollis - - f Deschampsia caespitosa - - one plant D. flexuosa la Pteris aquilina f (4) Bilberry association (Vaccinietum myrtilli). This is prob- ablya mereaspect of theCallunetum. The principalreason for separating it is thatat Waldridgethe bilberrycontinues to existunder the brackenin manyplaces where the Calluna has disappeared,so thatit evidentlyfor some reasonpossesses greater power of resistingthe destructiveeffect of the bracken. Its listwhere it occursapparently free is as follows: Vacciniummyrtillus Id Calluna vulgaris a Deschampsia flexuosa a Potentillaerecta f Erica cinerea f Agrostisvulgaris f Theresemblance to theCallunetum is manifest.

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(5) Deschampsietum flexuosae. This again may representonly the degenerateresidue of a number of other associations. At Waldridge it is usuallyto be foundin a zonation at the edge of a Nardetumthat is furthest fromwater. This correlationis very complete,but at its lower edge the Deschamnpsietummerges into a dry Nardetum,and may be regardedas a facies of the latter. Further,the dominantplant occurs plentifullyin the Callunetumat the top of the Fell, thoughon the otherfells it is rare in the Callunetiim. Where the spread of the bracken appears to be limited at presentby high water content,the Deschampsiais generallyto be found as a narrowfringe separating the brackenfrom Nardus. This is not an invari- able rule, however,and bracken frequentlypasses into Nardetum without any intermediatezone of Deschampsita. At Beamish the nature of this association is totally-different. The dominantoccurs plentifullyin the plantationat the north end of the Fell, as also does bracken. From this it is but a shortstep to assume that both these plants also occurred on what is now heathland but was formerly plantation,and that whenthe treeswere felled they assumed local dominance, and are now strugglingfor the masteryunder the altered conditions. The soil is a sandy clay, with humus about 8 cms. deep. At some points at Beamish I have made marksin the groundto show wherethe brackenfront reached in the autumn of 1914, and thus to indicate the rate at which it spreads. At BirtleyDeschampsita flexuosa is a rare plant. It is locally dominant on some slightlyelevated spots in the rolled strip but nowhere else. At TinklerFell the plant is never dominant. The compositionof the association is as follows:

Waldridge Beamish Waldridge Beamish Hypericumpulchrum vr Rumex acetosella o Rubus idaeus o Salix aurita 1 (north) - R. fruticosusagg. 1 Betula tomentosa - f Galium saxatile f f Scilla nutans r Solidago virga-aurea - r Luzula campestris r Senecio sylvaticus vr Juncuseffusus - Id Campanula rotundifolia 1 Carex binervis o o Erica cinerea o r C. stellulata r E. tetralix o (northside) - Festuca ovina a vr (elsewhere) F. rubra f Vacciniummyrtillus r a Agrostisvulgaris a 1 Calluna vulgaris o (northside) a Anthoxanthumodoratum o vr r (elsewhere) Nardus stricta f vr Empetrumnigrum 1 (northonly) - Trisetumflavescens o Digitalis purpurea o Holcus lanatus - Teucriumscorodonia I I (top) Aspidiumspinulosum - o Ilex aquifolium vr

The numberof true heath plants at Beamish is so great that it seems likelythe Fell was heath beforeit was planted,or even that parts have never been plantedat all but have always been heath. The whole area is however markedas plantationon the map of 1850. Journ. of Ecology IV 13

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(6) Nardetum strictae occurs at Waldridge under four aspects, accordingto the nature of the soil and the water supply. The lists vary slightlyin the fourcases, and these mergeinto each othergradually at their margins. It covers perhaps a larger area at Waldridge than any other association except bracken. It always occurs nearer to water than either brackenor Calluna, and it is thereforeprobably separated from these through havinga greaterwater supply. In the slightdepression that containsBogs 1, 2 and 3, thisis particularlywell seen,for on each side the brackenis dominant: the water drainingfrom the hills passes over the lower parts of theirslopes to reach the valley, thus increasingthe supply there. In these circum- stances Nardus is foundto be dominantover the whole of the valley,passing into Juncus effususand Carex goodenowiiat the bogs and streams them- selves. Round the bogs the wet Nardetummay be recognisedby the large quantity of Juncus squarrosuspresent. When a Nardetumis developed on coarse sand, it usually passes at its lower edge into a Molinietum,but when the amountof clay presentis large,it morefrequently passes into a Juncetum effusi. The boundaryis veryaccurately marked by the surfaceof the water by whichthe marshyareas are floodedin winter. No Nardus seemsto grow where it is ever covered with water. Experimentsare at -presentbeing carriedout to test whetherthis correlationdenotes a directcausal connection or not. At Birtley,Nardus dominatesmost of the southernpart, save wherethis is held by Ulex and Calluna. The northernpart does not bear so much of it. In the southernportion it has certainlyspread to a considerableextent at the expenseof the Callunetum. At Beamish the Nardetum does not occur. The reason is probablythe historicalone, that Nardus does not ordinarilygrow in woods,and that since the plantationthat formerlycovered this area was cut down the Nardus has not yet had time to colonisethe ground. At Tinkler Fell, Nardus occupies a large area; indeed it and Calluna cover nearly all the Fell. As elsewhere,it occupies somewhat lower and accordinglydamper ground than does Calluna.

Compositionof the Nardetum

Waldridge Birtley Tinkler -, - -Fell Fine sand and clay Coarse sand

Dry Wet Dry Wet Ranunculusflammula o 0 Cardaminepratensis I Viola palustris I Polygala vulgaris - o Ulex europaeus r Lathyrusmontanus vr vr Potentillaerecta - f - f f f Hydrocotylevulgaris - a - f

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Compositionof the Nardetum(continued) Waldridge Birtley Tinkler

______A______Fell Fine sand and clay Coarse sand Dry Wet Dry Wet Galium saxatile a I a Scabiosa succisa I- f Hieraciumpilosella la - - H. murorum f Cnicus paluster f Leontodon autumnalis a Achilleaptarmica o Campanula rotundifolia r Calluna vulgaris o o vI f to a o Erica tetralix o o E. cinerea - o - f Vacciniummyrtillus I o Euphrasia officinalis a Rumex acetosella r r Salix repens - f Luzula multiflora - f f f L. campestris o - - - _ Juncuseffusus o - o J. conglomeratus - 0 J. acutiflorus - o f J. supinus - - Isd J. lamprocarpus f- J. bufonius - - Isd J. squarrosus vr vr f id o Carex leporina o C. intermedia - - r r C. binervis - r - r C. panicea - o Festuca pratensis r - f F. ovina a f a f - F. rubra a o f Anthoxanthumodoratum - a to Id o a - a Agrostisvulgaris f f sd f Deschampsia flexuosa a sd r Triodia decumbens f f f Holcus lanatus o o H. mollis - f f Equisetum palLstre o - o Juncussquarrosus becomes dominant on the damp groundnear the south end of BirtleyFell. A peaty humus morethan six inches deep occursthere. The typical Nardetumis on much drierand coarserhumus, generally about threeinches deep. (7) The Whin association (Ulicetum europaei) occursat Waldridge principallynear the easterncorner, and in the disused Smithydenequarries. It is exceptionallydifficult to determineto what extent Ulex is a native,and no definiteconditions of soil and watercan yet be laid down that will deter- mine its occurrence. It growsluxuriantly high upon the pit heap (Hill 11), wherethe nutritivesubstances and the water contentare both so low that only Festuca rubraof the ordinaryheath plants seems able to grow,and that sparsely. Again,it growson actuallysubmerged ground in Bog 4, so that the range in whichit can growis evidentlyfar greaterthan what occurs in the heath. Attemptsto limitit to clay or to sand are equally fruitless. 13 -2

This content downloaded from 188.72.126.25 on Wed, 25 Jun 2014 09:31:36 AM All use subject to JSTOR Terms and Conditions 188 The Vegetationof four Durham Coal-Measure Fells Being a shrub,Ulex has the correspondingadvantages and disadvantages. The principaladvantages are (1) the ordinaryherbaceous plants are unable to rise above it and crowd it out; (2) its lowest branchesgrow close to the ground, and leave little room for any herbage below, thus facilitating spreading; (3) as it is a leguminousplant, it is independentof the nitrogen supply in the soil. Its principal disadvantage,however, is that it has to regenerateitself from seed. This leads to two furtherdefects:-(1) the seed is heavy, so that rapid spreadingis difficult;(2) the young plants are herbaceous,grow slowly, and are rathersensitive. Thus Uliceta somewhatresemble woodland in theirecological characters. The spread of Ulex mustbe largelydetermined by the facilityof distribution of the seed. Viewed in this light the distributionof Ulex on BirtleyFell becomes of special interest. It accuratelyfollows the wire fencethat sepa- rates the Fell fromthe road on the easternside; there are very few gaps, the principalbeing near the forkin the road. The Ulex area is a strip of nearlyuniform width, and about fiftyyards across. It is difficultto resist the opinion that in some way Ulex once succeeded in establishingitself either along this fence or along the disused waggon way parallel to it, and is now spreading at a fairly constant rate. A small gutter runs outside the fence,and it is possible that this may have originallyserved to distributethe Ulex seeds along its whole length. In addition to this area, Ulex occurs at the base of Shadon's Hill and on the Hill Pit heap. On account of the facilitywith which apparently bird-sown Ulex can colonise bare ground,it is likely that it originallyestablished itself on the Hill Pit heap, and has since spread fromthat point. On the othertwo fellsno whin association occurs; indeed Ulex is there a rare plant. The compositionof the associationis as follows VTaldridge Birtley Waldridge Birtley Ranunculus repens o o Hypochaerisradicata f f R. flammula - o Erica cinerea r o Viola sylvestris o Calluna vulgaris o Linum catharticum - I Digitalis purpurea o Stellariaholostea r - Teucriumscorodonia f - S. graminea o - Rumex acetosella f a Cerastiumtriviale - o Salix repens f to Isd Genista anglica r Luzula multiflora o Rubus fruticosusagg. f Juncuseffusus f R. idaeus f Carex goodenowii o Rosa canina r C. flava I Potentillaerecta r a C. leporina r Pimpinellfnziifrin.! o - Agrostisvulgaris a Galiumni-i.i i c Anthoxanthumodoratum a o Scabiosa succisa f Holcus mollis f f Achillea ptarmica - o H. lanatus a Solidago virga-aurea I 1 Molinia coerulea f Senecio jacobaea I Pteris aquilina f vr Cnicusarvensis f Aspidiumspinulosum r C. paluster r- f Ophioglossum vulgatum vr Hieraciummurorum r - Equisetum arvense vr H. umbellatum vr

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(8) Holcetum mollis. This association occurs in scattered patches in many parts of Waldridge Fell. The principal is in a slight depression near the summitof Hill 13, whereits developmentis due apparentlyto the presenceof rabbits,which attack this plant less than almost any other. It also occursin many parts of the lower slopes of hills at both Waldridgeand Beamish. The dominantcovers most of the groundin many of the plantations,but seems to be sharplylimited where the slope becomessteep. Steep slopesin plantationsand woods are generallytenanted by Pteris,Deschampsia flexuosa and Aspidium filix-mas. Holcus mollis also grows under all the hawthornbushes at the base of the Cong Valley, although these are sur- rounded by Deschampsiaflexuosa. It is locally dominanton the west side of Shadon's Hill, on some damp places of small gradient. From these facts it appears likely that a large quantityof organic matterin the soil tends to favour Holcus mollis; this has since been verifiedexperimentally. In addition, this plant is among the firstto colonise a burnt area, and it is favoured by shade, at the expense of its ordinarycompetitors. Its ecological relationsare thus very complicated. In the absence of all the dis- turbingfactors that favourit, it is unable to hold its own, but when they enter,it becomesa veryimportant member of the groundflora. The Holcetum mollis of summitof Hill 13 has Potentillaprocumbens o, Rubusfruticosus agg. r, Galium saxatilea, Calluna vulgarisr, Urticadioica r, Juncus effususo, J. squarrosuso; while under the hawthornbushes the ground vegetationconsists of Viola sylvestriso, Lychnis diurna o, Senecio sylvaticus1 plant, Digitalis purpurea 1 plant, Agrostisvulgaris f, Holcus mollis cd, Pteris aquilina cd. The violet and the campion here mentioned occur also sparinglyunder the brackennear by. (9) Molinietum coeruleae occurs principallyround the outlet of the Wanisterbog. It is developed on a fairlydeep stratumintermediate in characterbetween humus and peat. The damperparts mergeinto an associa- tionof Carex goodenowii, but thetransition is gradual,and too muchreliance must not be placed on the separationinto two associations. It occursagain in the depressionthat surroundsHill 9, and in one bog on the northernslope; thisbog is peculiarin that Nartheciumossifragum is subdominant. All these spots are eitherin depressionsor else suppliedwith water with a highcontent of organicmatter; the water contentand the organiccontent are therefore both presumablyhigher than in the surroundingparts, which are generally Nardetum. In a small bog near the ChesterMoor road Carex goodenowiiis in almost pure dominance. The associationsare composedof the followingspecies:

MolinietumCaricetum MolinietumCaricetum Ranunculas flammula o o Lotus major f Cardaminepratensis r f Potentillaerecta o Viola palustris f f Hydrocotylevulgaris f a Sagina nodosa f Galium uliginosum -.

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MolinietumCaricetum MolinietumCaricetum Valeriana dioica - f Nartheciumossifragum r to Isd Scabiosa succisa f a Triglochinpalustre f Cnicuspaluster f - Carex goodenowii a d Achillea ptarmica - o C. stellulata o sd Calluna vulgaris if - C. panicea o a Erica tetralix If - C. flava a Empetrumnigrum if - C. pulicaris vr Menyanthestrifoliata - a Anthoxanthumodoratum a to Id Anagallistenella - r Nardus stricta f - Pinguiculavulgaris - f Festuca ovina o Juncussupinus Molinia coerulea d var. fluitans - o Holcus lanatus f J. obtusiflorus f Briza media o J. squarrosus o Aspidiumspinulosum I Luzula multiflora o o Equisetum sylvaticum I Scirpus caespitosus f Sphagnumspp. o Orchisericetorum - f (10) Oak-Hazel Wood occurs on the steep slope (in some places quite precipitous)on the northernslope of the Fell. The soil is a sandy clay, and usually very dry,except whereintermittent streams are running. The exposed rocks are a hard jointed shale. Most of the trees are small, and none exceed 30 feet. List :-Quercus sessilifiorasd, Corylus avellana d, Betula alba Id, Crataegusmonogyna f, Rosa canina f, Fraxinus excelsiorr, Holcus lanatusf, Deschampsiaflexuosa f. On a level part of the bank just above this wood, Salix aurita occurs in large quantity,and with it its hybridswith S. caprea and S. cinerea. Only one plant of pure S. caprea has been found. A dry Nardetumsurrounds this thicket. A somewhatsimilar thicket occurs on a flatpart at the base of the hill,where the followingoccur :-Salix aurita a, S. caprea 1 plant, S. cinerea 2 plants, Holcus mollts d, Festuca pratensis a, Agrostisvulgaris a, Pteris aquilina f. (11) Hawthorn Scrub. On the steep slope of the detached portion, where landslips are frequentlyoccurring, an open hawthornscrub is developed. The soil is fine sand, which is full of small apparentlywater-worn bouldersat the top. List :---Ulexeuropaeus f, Cytisusscoparius o, Crataegus monogynad, Rosa dumetorumo, R. villosa vr, Rubus idaeus o, Sambucus nigerf, Fraxinus excelsior(young) o, Agrostisvulgaris sd, Holcus mollisf, Deschampsiaflexuosa sd, Pteris aquilina sd. The very small stream num- bered 14 has many hawthornbushes on its banks; very few occur among the surroundingbracken. (12) Marsh associations. Examples of these in this area are nine in number,and little more than a sketch of them will be given here. The alder, birch,and Salix cinereawoods may also be included in this section. As thereseems to be little necessaryecological connectionbetween marshes that are not connectedby watercourses,the simplestmode of treatmentis to deal withthem geographically in a convenientorder. Bog 4, near the most easterlycorner of WaldridgeFell,, differs from all the other marshesin the comparativepurity of its water, which is almost

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colourless. Stream 10, whichflows through it, is a rapid streamand appears to be deep-seated,as it never becomes dry even in summer. An analysis of the water of the bog was made in June,1915, to findthe organicmatter, the acidity,and the dissolvedoxygen. Onlya roughtitration with permanganate and sulphuricacid was made to findthe reducingstrength of the organic matter present. The dissolved oxygen was found by Winkler's method'. It was found that the reducingstrength was equivalent to less than Totg normal permanganate,the dissolved oxygen amounted to 2-6 c.c. per litre, and the acidity, estinmatedwith caustic soda and phenolphthalein,was 3-4 x N x 10-4. The mineralcontent is low in all the watersexamined, and is mainlydue to iron. The centreof this bog and that of the upper part of the issuingstream are dominatedby a dense growthof Epilobium hirsutum. No other plant grows among it. Round the edges a differentassociation occurs in the shallow water, dominated by Juncus glaucus. The compositionof this in the bog is as follows: Ranunculus repens a Ulex europaeus 1 bush Senecio aquaticus o R. flammula o Epilobium tetragonum Mentha aquatica a Nasturtiumofficinale a var. obscurum o Poa trivialis a Cardaminepratensis r Ulmaria palustris o Deschampsia caespitosa f C. flexuosa r Galium palustre f Carex goodenowii Cerastiumtriviale f Cnicus paluster f Equisetum palustre o Lotus major f Tussilago farfara o

Round the outlet the vegetation is not so close, and the only plants growing are Nasturtiumofficinale sd; Glyceriafluitans Isd; Ranunculus lenormandia. The plants associated withJuncus glaucus in the upper part of the stream are verydifferent. They are:-Ranunculus repens,Stellaria utiginosa, Hydro- cotylevulgaris, Senecio aquaticus, Veronica beccabunga,Stachys sylvatica, Myosotiscaespitosa, Holcus lanatus,Triglochin palustre. On the marginof the streamis a fringeof Juncusacutiflorus, merging to Scirpus palustrislower down, with Equisetum limosum occasional and Lychnis flos-cuculifrequent. Bog 7, near the mostwesterly corner of the Fell, lies at the bottom of an almostprecipitous slope. The soil underit seems to be clay, whilethe water does not seem much differentfrom that in Bog 4. The vegetation,however, is altogetherdifferent:-Sparganium ramosum d, Ranunculusflammula f, Cardaminepratensis o, Galium uliginosumf, Veronicascutellata o, Potamo- geton natans a, Eleocharis palustris a, Glyceriafluitans sd, Equisetum limosumsd, Sphagnumsp. a. Juncus effususis dominantround the edge. This vegetationis very similar to that of the ponds in disused clay-fields in the same district. Pond 13 is supplied with water fromthe boilers of the collieryengines,

1 Purvis and Hodgson, Water,Sewage, and Foods, Cambridge,1914, p. 46.

This content downloaded from 188.72.126.25 on Wed, 25 Jun 2014 09:31:36 AM All use subject to JSTOR Terms and Conditions 192 The Vegetationoffour Durham Coal-Jleasure Fells and cannot be regardedas natural. In it Glyceriafluitans and Alopecurus geniculatusare co-dominant. Bogs 1, 2, 3, 6, 9, 10, and 12 are all occupied by Juncus effusus. The water of all of them is stagnantwhile it is present,but usually dries up in summer. There is no underlyingpeat. The associated species are few,the chiefbeing Juncus bufonius,Carex goodenowiiand Agrostisalba. The last is locally dominantround the marginof Pond 10. Streams8 and 9, and most of the otherintermittent streams, have their beds,covered with a wet Nardetum,with Anthoxanthum,Deschampsia caespitosa, Carex panicea, C. flava, and Hydrocotyle.In many places Juncus effususoccurs in the centre. Its leaves are very dry in summer,and much brackengrows among it. Nearly all this brackenhas the ends of its leaves withered. No bracken occurs in the Nardetum, although it is usually dominant on the other side of the Nardetum. The sides of the South Burn above the ChesterMoor entranceare lined with spontaneouswoods of Alnus rotundifolia,Salix cinereaand Betula alba. The alder occupies most of the left bank to a distance of about 30 metres fromthe stream. The soil is verywet, with a largeamount of organicmatter. The florais veryrich. List: Ranunculus repens f Scrophularianodosa o R. flammula f Veronica chamoedrys o Lychnisdioica f Digitalis purpurea f Hypericumtetrapterum o Pedicularispalustris a Geraniumrobertianum o Ajuga reptans o Acer pseudoplatanus r Stachys sylvatica o Oxalis acetosella f Prunella vulgaris f Trifoliumrepens f Menthaaquatica f Lotus major f Lysimachianemorum o Vicia cracca o Alnus rotundifolia d Crataegusoxyacantha f Salix cinerea sd Spiraea ulmaria f S. caprea vr Pyrus aucuparia f S. aurita a Rosa canina 0 S. pentandra a Rubus idaeus f Rumex conglomeratus f Epilobium palustre o Juniperuscommunis f Chrysospleniumoppositifolium o Callitrichesp. o Oenanthecrocata o Orchismaculata f Galium cruciatum f Juncuseffusus o G. palustre o Luzula svlvatica f Viburnumopulus a Carex vulpina f Lonicera periclymenum f C. leporina f Valeriana dioica f C. laevigata f V. officinalis f C. paniculata a Eupatoriumcannabinum a Glyceriafluitans o Lapsana communis f Holcus mollis a Solidago fv:i n1irea f Deschampsia caespitosa a Menyantl i XIdI . ' s la Equisetum sylvaticum a Fraxinus excelsior o Aspidiumfilix-mas f On the otherbank rmostof the groundis occupied by a ratheropen birch wood, with Holcus mollisor Deschampsiacaespitosa subdominant, according to the dampnessof the soil. The rest is covered withSalix cinerea,but the groundflora is so similarto that of the alder wood that it seems possible that the willowthicket may have only arisen in consequence of the partial

This content downloaded from 188.72.126.25 on Wed, 25 Jun 2014 09:31:36 AM All use subject to JSTOR Terms and Conditions H. JEFFREYS 193 fellingof a previouslyexisting alder wood'. Some alder trees still stand. All these woods are confined.to the base of the hills, and cease abruptly wherethe gradient,becomes great. On Birtley Fell there are few, if any, natural streams, but numerous ditches have been cut. These have a characteristicvegetation, of a very open type. The water is fairlypure, but acid. List:- Ranunculus flammula a Senecio aquaticus a Cardaminepratensis a Myosotiscaespitosa f Sagina proeumbensagg. f Veronica buxbaumii o S. nodosa I Juncuseffusus f Stellaria media Isd J. lamprocarpus f S. uliginosa I J. obtusiflorus f Lotus major f Carex panicea I Peplis portula 1 C. flava I Hydrocotylevulgaris f Poa annua f Gnaphaliumuliginosum f Agrostisalba Id Cnicus paliister a In the true bogs a differentassociation occurs, reseniblingmost the Glyceriapond at Waldridge,although it is morenatural. List - Ranunculus drouetii Id Juncuseffusus f Scirpus setaceus I R. lenormandi I J. conglomeratus f Alopecurusgeniculatus 1 Helosciadiuminundatum 1 J. supinus f Glyceriafluitans f AMyosotiscaespitosa f Carex panicea *f Sphagnum'sp. J Juncusbufonius a C. flava f The small merescontain very peaty water. The vegetationof theirbeds consists mainly of Carex goodenowiiand C. panicea; Juncus squarrosus, Calluna and Nardus occur round the edges. Usually no true water plants occur, but sometimesRanunculus flammula and the wet-growingform of Agrostisalba are to be found in the bottom when the water has nearly dried up. The sides are sometimeslined with Molinia, Erica tetralix,and Juncus squarrosusabove the level of the water, while Nardus and Calluna come down to the upper edge of the Molinia zone. Wanister Bog (Bog 11) is the largest of the Waldridge bogs. It occupies the flat ground to the east of the Wanister Hill, and varies con- siderablyin size duringthe year. It is' smallest in September,and largest in May. When it is fullestthe depth may reach halfa metre,but sometimes the whole becomesdry. The wateris brownand stronglyacid. An analysis

in June, 1915, showed that the reducing strengthwas 2N0 the dissolved oxygen 2-1 c.c. per litre, and the acidity 13*2x N x 10-4. The principal inletsare intermittentstreams dominated by Juncuseffusus. The bog itself is fullof the unbranchedform of Equisetumlimosum. The list of the associationis as follows:-- Ranunculus flammula o Menyanthestrifoliata f Carex goodenowii 0, R. repens f Juncussupinus f C. stellulata o Epilobium palustre o Potamogetopllritei i a Equisetum limosum d Hydrocotylevulgaris a Eriophorumn ':iIii o Sphagnumsp. sd

1 CompareTansley, A. G., Types of BritishVegetation, Cambridge, 1911. 13-5

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The cotton-sedgeten years ago was vastly moreplentiful than it is now. The bottom of the bog is pure peat, and is very powderywhen the water driesup. Much marshgas risesfrom the decomposingmatter at the bottom. Where the Eriophorumgrows the depth in June, 1915, was about 15 cms. The Equisetumnall over the bog rose a uniform40 cms. above the surfaceof the water. About Augustall the stems of this plant die and collapse. At the top end of the bog is a -Caricetumgoodenowii of the following composition: Ranunculusflammula f Carex goodenowii d R. repens f C. stellulata f Cardaminepratensis f Scirpus setaceus o Hydrocotylevulgaris sd Anthoxanthumodoratum a Cnicus paluster o Festuca pratensis o Menyanthestrifoliata, a to sd F. rubra vr Juncuseffusus f Holcus lanatus o J. acutiflorus a Equisetum limosum a Luzula multiflora o Streams 5 and 7 have theirsources in this bog. Most of theirlength is occupied by an association dominated by Juncus acutiftorus.The streams are movingrapidly where this occurs,and most of the plants growwith their rootspermanently submerged. List:- Ranunculus acer o Juncusobtusiflorus f R. repens o Eriophorumangustifolium r R. flammula f Carex flava o Cardaminepratensis r C. panicea f Hydrocotylevulgaris a C. stellulata f Taraxacum officinale o C. goodenowii a to Id Cnicus paluster o Glyceriafluitans f Triglochinpalustre f Festuca rubra o Juncusacutiflorus d Anthoxanthumodoratum f J. lamprocarpus f Equisetum limosum ld J. supinuswith v. fluitanso ER palustre f At the edges this association passes into a Molinietum,and then to Calluna and bracken. A differentJuncetum effusi, with many associated species, occurs in the lowerpart of Stream7, the compositionbeing as follows: Ranunculus acer f to a Cnicus arvensis f Caltha palustris f Mentha aquatica f Cardaminepratensis a Ajuga reptans f Viola palustris f Rumex acetosa o Vicia cracca o Salix cinerea o Ulmaria palustris a Orchisericetorum o Hydrocotylevulgaris a Juncuseffusus d Angelicasylvestris o J. glaucus f Valeriana officinalis f J. acutiflorus(at margin) Id Crepispaludosa r Carex remota o Tussilago farfara o Aspidiumspinulosum f Cnicuspaluster f The marginalassociation is the wet Nardetum. Where the gradientis verv small, Eleocharis palustris becomes dominant. The same plant is dominantwhere Stream 5 spreads out into a broad spongy bog, but the associated species are totally different.

This content downloaded from 188.72.126.25 on Wed, 25 Jun 2014 09:31:36 AM All use subject to JSTOR Terms and Conditions JOURNAL OF ECOLOGY VOL. IV, PLATE XI

H41

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This content downloaded from 188.72.126.25 on Wed, 25 Jun 2014 09:31:36 AM All use subject to JSTOR Terms and Conditions H. JEFFREYS 195

The Scirpetumof the slowlymoving stream includes: Ranunculusrepens f Taraxacum\officinale r Eriophorumangustifolium vr R. flammula f Cnicus paluster f Deschampsia caespitosa o Rubus idaeus a Juncusglaucus I Glyceriafluitans a Hydrocotylevulgaris a J. effusuis a Equisetum palustre a The Scirpetumof the acid bog includes: Cardaminepiatensis Valeriana dioica Salix cinerea Lychnisflos-cuculi Crepispaludosa Orchisericetorum Angelicasylvestris Senecio aquaticus Juncusglaucus 1 Galium palustre Menyanthestrifoliata J. acutiflorus cd G. uliginosum Myosotispalustris Eleocharis palustris cd Valeriana officinalis Pinguicula vulgaris The study of the numerousconstituent associations of the marshforma- tion thus appears to be a matter of considerablecomplexity. It appears probable howeverthat the followingsuggestions may afforda usefulbasis of subsequentinvestigation. (1) A clay soil, permanentlysubmerged, tends to favour Sparganium ramosum. (2) Ground that is very wet, usually submerged, in winter,and badly drained, or else supplied with water with a high content of organic matter,favours Juncus effusus. (3) More rapid drainage, combined with a higher supply of organic mlatter,favours Juncus acutiflorus. (4) Deeper water of the same type as the last favours Equisetum limosum. (5) Shallow water, with a very small amount of organicmatter, or acid, favours Juncus glaucus. (6) Somewhat deeper water of the same type favours Epilobium hirsuturn. (7) A less permanent supply of pure water favours Glyceriaaquatica and Alopecurus geniculatus. (8) Slowly moving permanent acid streams and a very wet type of acid bog favour Eleocharis palustris. The materialavailable is inadequate to establishwhether these relations are general. They account adequately forthe distributionof the herbaceous associations of the marsh formationin the areas considered,and do not appear to be contradictedby observationselsewhere. Until more detailed treatment,preferably by experiment,is possible,they are offeredtentatively as the simplestset of hypothesesthat satisfythe observedconditions.

DESCRIPTION OF PHOTOGRAPHS ON PLATE Xi Phot. 1. Zonation at Stream 10. Juncus glaucus in bed of stream, with Nardus at the edges. On the left this passes to Ulex and then to Deschampsia flexuosa and Pteris aquilina. Bog 4, with Epilobiumnhirsutum, is just visible in the back- ground. Phot. 2. Base of Wanister Hill (Hill 2). Bracken dominates the slope, and is cut off sharply at the bottom, where it changes to Holcus lanatus. Phot. 3. Zonation beside the Wanister Bog. Bracken on the right,Juncus acutiflorusin the edge of the bog on the left,with a light coloured intermediatezone of Nardus. The grass with the conspicuous white heads is Anthoxanthumodoratum. Phot. 4. The Wanister Bog, with Hill 4 behind it. Pale area of Equisetum limosum in the centre, passing to Eleocharis palustris, and then to Carex goodenowiiwith Juncus acutiflorus. Potamogetonplantagineus occurs in the open area in the fore- ground. On the hill behind, the upper part is dominated by bracken, and the lower by Nardus, with some Juncus effususin the beds of the streams.

This content downloaded from 188.72.126.25 on Wed, 25 Jun 2014 09:31:36 AM All use subject to JSTOR Terms and Conditions