Ecological Flora of the Central Chilterns

Transcription

1 Ecological Flora of the Central Chilterns Book III: Spore-bearing Plants Adder's-tongue fern, Prestwood Picnic Site Tony F Marshall, M.A. (Cantab.) August 2014

2 Book III Spore-bearing plants In evolutionary terms these are the earliest and most primitive of our plants. The shed spores develop in a film of water into tiny green plants called gametophytes. These produce small male sperm cells and larger female egg cells, the former maturing first so that they will fertilise the egg-cells of gametophytes other than their parental ones by travelling through the film of water, ensuring cross-fertilisation. They are therefore more dependent on a wet habitat for reproduction than the seed-producing plants. Frosted fronds of male fern, December

3 Family: Lycopodiaceae (Clubmosses) 10.2 Stag's-horn clubmoss Lycopodium clavatum This inhabitant of heathy woods was last recorded locally in 1974 in Monkton Wood and in 1973 in Lodge Wood (in both cases by the late Ted Byrne). It has not been recorded anywhere in the Chilterns or Buckinghamshire since 1974, when it was also recorded in Hillock Wood, just outside our area but neighbouring Monkton Wood. It must therefore be considered extinct in the Chilterns, as it is from virtually all the lowlands, it remaining common only in the north and west of Britain. The location in Lodge Wood was carefully checked in 2001, as it was clearly identified by Mr Byrne, who saw six plants growing under beech with heather beside forestry ruts. A few plants of heather survived, although they were attenuated by the lack of light consequent on increasing conifer cover, and these have also since disappeared. The plant was more extensive in Monkton Wood, where Mr Byrne saw it at three separate locations. One small patch in 1973 under beech with heather and heath bedstraw was not rediscovered in In 1974 there was one 25msquare patch under young beech and conifers where the clubmoss was said to be "abundant" and nine plants under regenerating beech by open tracks at another site. It appears likely that increasing shade was the reason for its demise there, just as it clearly was in Lodge Wood. When producing spore-bearing cones stag'shorn clubmoss is unmistakable, although purely vegetative procumbent shoots can easily be overlooked as moss. There is a record in BMERC of fir clubmoss Huperzia selago from Lodge Wood in This is unlikely to have ever occurred in our area and must have been a clerical or identification error for Lycopodium clavatum. Druce (1926) does not mention stag's-horn clubmoss for our area, so it is likely that it always existed in small quantity, probably varying according to alterations of light through forestry operations. Stag's-horn clubmoss growing in Scotland Family: Selaginellaceae (Lesser clubmosses) Krauss's (Mossy) clubmoss Selaginella kraussiana Discovered by Patricia Strugnell for the first time in Bucks in 2017, naturalised in a garden at a former farmhouse on Church Lane, Great Missenden. This tropical species, which is very moss-like, is sometimes used as ground cover and may also be introduced accidentally with pot plants from garden centres. It is creeping, well-branched, rooting as it spreads, and thus matforming, and in sheltered situations surviving our winter. It is also well established at Savill Gardens, Windsor. The leaves are in four ranks, two larger ones patent, two half the size more or less appressed to the stem (see picture below).

4 10.3 Mossy clubmoss showing 4-ranked leaves Family: Ophioglossaceae (Adder's-tongues) Adder's-tongue Ophioglossum vulgatum This rare plant has been recorded at only seven sites in our area, of which only two are probably extant. It was not mentioned by Druce (1926) and was probably always scarce. It is dependent on undisturbed established grassland that has not been fertilised. Locally it occurs on thin chalk soils and in this situation remains a small plant, just a few centimetres high, much lower than the maximum 30cm or more leaf-blade given in Stace (2010). Identification Unmistakable low plant easily overlooked when growing amongst grass. From the base of a single oval leaf-blade appearing in May arises an unbranched fertile spore-bearing stem that ripens yellow June-July. Notable sites Currently known only at Prestwood Picnic Site, where it was discovered by Peter Daltry in 2011, and in similar native chalk grassland in the back garden of a house on Perks Lane, on the hillside opposite to the Picnic Site (George Lewis, first seen 2004). The fact that these are very recent discoveries in well-explored locations raises the possibility that the plant is a recent arrival by spores from some other nearby site so far undiscovered. All other records are from the 1960s-1980s. In the 1980s it was seen in grassland near Naphill and Speen, but the 1960s records are all from open woodlands that have since shaded over (all had been planted to conifers) and are now unsuitable. Ecological associates No galls or mines are known, and no other associates have been noted locally. Human associations It was traditionally supposed to have been used for healing wounds, but, despite the association of the name giving it that reputation, it would have been of no use in curing adder-bites. Derivation "Adder's-tongue" is a direct transliteration of the Latin ophioglossum, referring to the supposed resemblance of the narrow fertile spike to a snake's tongue (although it is not forked). Another folk-name was Christ's spear. Adder's-tongue at Prestwood Picnic Site

5 Family: Equisetaceae (Horsetails) 10.4 Horsetails were the dominant plants during the Carboniferous era, but they are much less prominent today. All species exude crystals of silica on their stems, making them rough to handle. Field horsetail Equisetum arvense Abundant in many areas of Britain, field horsetail is a rare plant with us. Less dependent on water than our other native horsetails, it is typically in our area a prostrate weedy plant of rough ground and wasteland. It may once have occurred along the River Misbourne when the adjoining fields were wetter, as Druce (1926) considered it "abundant" in our area. Identification There are two types of growth - sterile grooved (6-9 ridges) green stems, upright or sprawling, with bushy simple branches, and pale brownish simple (unbranched) stems topped with sporeproducing cones (<4cm) which usually appear earlier in April. The latter have regular sheaths up the stem with 6-20 dark teeth. I have rarely seen fertile stems produced in our area, which may explain its scarcity, although the lack of fertile stems itself requires explanation. Notable sites This plant is best seen in the hedge along the boundary of the houses on the south side of Green Lane. It also grows in our area by Prestwood Village Hall and in the pavement by the main Missenden road in Great Kingshill. It is well-established at the Sports Centre car-park (first recorded 1996). In many cases it grows in areas that are regularly cleared of vegetation; although the roots survive, it is rarely allowed to grow to any height. That in Great Kingshill grows only in a prostrate dwarf form. Ecological associates None known. Human associations Known as a styptic in folk medicine, it has also been boiled to produce a fungicide (Mabey 1996). Derivation The name comes from a fancied resemblance of the bushy fertile stems to horses' tails. Rough horsetail Equisetum hyemale Native to Britain but not to the Chilterns, this horsetail, also known as Dutch rush, may be planted in or by garden ponds. It is extant at one site in our area, in a garden pond on Orchard Lane, Prestwood. It grows simple unbranched green stems that develop a small cone at the tip. The sheaths up the stem are black at the tip and the base and paler in between and soon lose their teeth. The stems are rougher than any of our other horsetails and have up to 30 ridges. The stems are useful for emerging dragonfly larvae - see the picture, right, which shows the exuvia of a broad-bodied chaser Libellula depressa. Field horsetail Field horsetail in prostrate form Water horsetail Equisetum fluviatile This generally common aquatic horsetail was said by Druce (1926) to be "very common by water" in our region, but I have come across no records for the area. It quite probably once grew along the Misbourne near Little Missenden. The green stems are often simple or irregularly branched, have ridges, and pale green sheaths with small whiteedged black teeth. Rough horsetail in garden pond, Orchard Lane

6 Family: Dennstaedtiaceae (Bracken) 10.5 Bracken Pteridium aqualinum This fern is widespread in our area in woodlands on somewhat acidic soil. Druce (1926) said it was "abundant except on chalk, clay". In the first half of the 19th century it was dominant on much of the common land in our area, growing on the poor soils of sandy clays at Prestwood, Great Kingshill, Heath End and Denner Hill but these were all lost to agriculture at the time of the Enclosures and (except Denner Hill) subsequently used for housing. The current distribution shows that bracken is not averse to clay or even chalk substrates as long as the soil has been leached, does not get waterlogged, and there is enough light. It can be invasive (eg Hampden Common), spreading by tough underground root-stocks that are notoriously difficult to eradicate. Identification Our only fern that has its main stalks branched in more or less horizontal opposite pairs, these branches forming 2-pinnate fronds, the ultimate pinnules being narrow and wavy edged. It can grow to above head height in late summer and its tough fronds survive as brown debris through the winter. Notable sites It grows commonly in hedgerows, eg Hampden Road, Nairdwood Lane (south) and by the lane to Denner Farm from the top of Rolls Lane, as well as most woodlands (eg Hampden Coppice, Atkins Wood, Sandwich Wood), where it can form extensive patches. NVC In open areas on free-draining acidic soils bracken can form the dominant component of U20 Pteridium-Galium communities, often accompanied by heath bedstraw Galium saxatile, tormentil Potentilla erecta and sheep's fescue Festuca ovina. This would have been one of the communities on the former commons, but this habitat has been lost in our area. It is also the dominant in W25 bracken/bramble underscrub in cleared woodland and under hedges, one of its main communities in our area. In these communities it is often accompanied by bluebell Hyacinthoides non-scripta which can get away to flower before the bracken fronds unfurl and shade out most other ground plants. It is sub-dominant in W10 oak/bracken/bramble and W16 oak/birch/wavy hair-grass woodlands, relics of which survive in our area despite the general replacement of oak by planted beech. Galls Five galls have been described in this country, but none have so far been recorded locally and should be searched for. Mines Four leaf-miners have been described, one of which is also a gall-causer. The mines of the fly Chirosia histricina have been recorded locally on bracken (Nairdwood Lane). Other ecological associates Although one of our most common plants, bracken has a limited number of invertebrate associates because of its toughness. The moths Brown Silver-line and Small Angleshades feed on bracken as caterpillars and have been recorded locally, as has the sawfly Tenthredo colon, which shares this habit. Heath damsel bug Nabis ericetorum has been recorded on bracken (Atkins Wood) and the small fungus Rhopographus filicinus grows on the dead stems of bracken in the autumn and winter. Tracts of bracken make excellent cover for many birds and mammals such as roe deer and muntjac. Human associations When bracken was abundant on local commons it was collected by cottagers as bedding for themselves and their animals, having the advantage that it was inimical to fleas. Bracken contains cyanides and may be carcinogenic, so that former uses in folk medicine may have been accompanied by some risk, although it has been used as fodder for cattle. The ash from burning green bracken was used to make a fertiliser high in potash and dried fronds can be used as a mulch or cover for vegetable plots. For these purposes bracken was once extensively cut, helping keep it under control, whereas nowadays its spread is a major threat to conservation. Derivation In Middle English the word was braken and "brake" is still a dialect name; the origin seems to be in Old Norse but the connotations of the term are not known. Varieties Our plant is sub-species aquilinum, which is the common sub-species in Britain except perhaps for the Scottish Highlands. Bracken, Hatches Wood Showing veins in pinnules reaching edge of frond Young frond

7 Family: Aspleniaceae (Spleenworts) 10.6 These are mainly wall-growing ferns. Hart's-tongue Asplenium [Phyllitis] scolopendrium This distinctive fern inhabits wet shady places such as north-facing church-walls, chalk-pits and roadside banks, widely distributed but not common (in Druce 1926 it is recorded as "rare" in our area). Identification The fronds are oblong, bright glossy green, up to 60cm long and grow in clusters. The spores lie underneath the frond in straight diagonal lines from the mid-vein or rhachis. They are quite tough and last well into the winter. Notable sites On most churches (especially the Zion Baptist Chapel in Prestwood), but in small numbers because of frequent wall-cleaning. Often on railway bridges. Larger colonies may be found along deep lanes with high banks, especially where chalk comes to the surface - eg Kingstreet Lane, Featherbed Lane, Perks Lane under Longfield Wood, and Broombarn Lane. It has also been found growing in a drain along Prestwood High Street and Church Street, Great Missenden. It rarely occurs in wet woodland (eg Peterley Wood after the wet winter of ). Ecological associates No galls and only three mines are known on hart's-tongue in Britain. Two of these mines, by the small moths Psychoides filicivora and P. verhuella have been recorded locally. No other associates have been noted. Human associations Although hart's-tongue has been used in folk remedies in Ireland and the west of Britain, it has never been frequent enough in our area to have attracted any particular attention. Derivation The frond is supposed to have the shape of a deer's tongue; it is also called fox-tongue in some localities. Hart's-tongue growing on a stony bank Wall-rue Asplenium ruta-muraria Much smaller but still distinctive fern entirely restricted to walls, where it is rather uncommon in our area. Identification Short tufts (to 10cm) of tough branched fronds with wedge-shaped segments which are themselves sometimes divided. Underside of frond covered with pale brown spores. Notable sites This fern is typical of brick railway-bridges all through Great Missenden and can be abundant there. It occurs more sparsely on church walls because it regularly gets "cleaned" off (eg just one plant on Great Missenden Parish Church in 2014). It is also established on old flint walls beside Lower Warren Farm, Stonygreen Cottage, Abbey Farmhouse in the Square, Great Missenden, and very few other places. Ecological associates No galls and the same three mines that occur on hart's-tongue are known on wall-rue but none have been recorded on that plant locally, nor any other associates. Human associations None. Derivation The fronds are somewhat reminiscent of the Mediterranean herb "rue".

8 10.7 Wall-rue typically growing on railway bridge brickwork Young leaves of wall-rue are less divided Maidenhair spleenwort Asplenium trichomanes Another small fern restricted to walls in our area, where it is even less common than wall-rue. Druce (1926) considered it "very local, rare" in our area. Identification Tuft of wiry dark brown stalks with the frond divided into small oblong pinnae. Notable sites This fern used to be found regularly on the railways bridges with wall-rue, but more sparsely, but it is now rarely found. Recent records are from Missenden Abbey and walls in a nearby garden, the railway bridges at the bottom of Whitefield Lane (2007, but not there 2014) and near Misbourne School, a wall in the High Street, and Hughenden Valley. A drier climate over the last few decades seems to have done this fern no favours. Ecological associates As for other Asplenium spp, but none recorded locally. Human associations None. Derivation The dark wiry stalk is similar to that of Maidenhair Fern, but it is otherwise quite distinct. "Spleenwort" refers to traditional remedies ("wort") for assumed disorders of the spleen, but this seems to have been an invention of old herbals and the only documented use, like other spleenworts, was for coughs and similar ailments, probably because of a similarity of the mucilaginous liquid obtained from boiling the fronds with the mucus produced in colds (the pre-scientific "doctrine of signatures" or the use of "like against like"). Its use was once well-known, for Alexander Pope references it in his "Rape of the Lock": "A branch of healing Spleenwort in his hand". Varieties Our plant is ssp. quadrivalens, the only form in chalk districts, differing from forms in the north or west and on acid substrates by the shape of the pinnae.

9 Black spleenwort Asplenium adiantum-nigrum 10.8 Another fairly small wall-fern almost as uncommon in our area as maidenhair spleenwort. It was not included for our area in Druce (1926). Identification This wall-fern is more fern-like than the others because of its much more divided "ferny" frond. Notable sites It survives in good numbers on the parapets where Martinsend Lane and Rignall Road go over the railway, but has almost disappeared from other railway bridges. It no longer grows on the church walls (eg Great Hampden) where it once existed (if sparsely), except for a single frond unlikely to survive long at Prestwood Parish Church. Ecological associates As for other Asplenium spp, but none recorded locally. Human associations None. Derivation "Black" refers to the base of the stalk, which is green in the rare Green spleenwort A. viride not present in our area. Rustyback Asplenium ceterach This very distinctive wall-fern is very rare in our area, where it has long been known from just one site. Identification The frond is divided into connected lobes, which tend to curl up to prevent water loss in our climate. The most distinctive feature is the dark brown spore masses that give it its name, completely covering the undersides, particularly obvious when the fronds curl up. Notable sites The flint wall of the ha-ha in the private grounds of Missenden Abbey. Rustyback at its one local site Family: Thelypteridaceae Lemon-scented fern Oreopteris limbosperma Recorded from Monkton Wood in 1974 by Ted Byrne, but not seen in any subsequent surveys. It was not mentioned for our area by Druce (1926). The habitat was once suitable, however, and there is no reason to doubt the record. It is like a smallish male fern (below) and could easily be overlooked. Its most distinctive character is the lemon scent when crushed. The nearest extant site to my knowledge is Black Park in the south of Buckinghamshire. There may no longer be any suitable habitat in the Chilterns.

10 Family: Woodsiaceae 10.9 Lady fern Athyrium filix-femina An attractive woodland fern, but easily overlooked. It occurs occasionally across our area in ancient woodland and was said by Druce (1926) to be "locally frequent" in the Hughenden and Kingshill areas. Identification The fronds are bipinnate like male fern, ie the main pinnae are deeply cut into pinnules, which are deeply and finely cut so as to look almost tripinnate, much more delicate and pretty in appearance than the male fern, hence the name, a survival from earlier more sexist times. The fronds can look surprisingly like the pinnae of bracken. The spore covers underneath fertile fronds are not round or kidney-shaped, but bean- or half-moon-shaped. The stalks have only small scattered scales. Notable sites It grows sparsely in most of our more ancient woodlands, particularly Piggotts, Monkton, Little Stocking and Gomms, usually along damp rides (eg Angling Spring Wood) and ditch-edges in leached or more acid places. Galls Only two galls are known nationally, of which one is very rare. The other, rolled fronds caused by the larvae of the fly Chirosia betuleti, is quite common locally. Mines Not known for certain in Britain. Other ecological associates None recorded. Human associations None, which probably shows that the species has never been really common. Varieties Lady fern was particularly known in the times of the Victorian fern-craze for its large number of sports. While this genetic variability may have been collected out, it may still be worth looking out for unusual forms. Lady fern Brittle bladder-fern, Great Missenden Brittle bladder-fern Cystopteris fragilis This is a very rare fern in the south and east of Britain and its occurrence in our area, at its only Buckinghamshire (and Chilterns?) site, is a subject for speculation. It may have been brought in with stone used for building, but it may also be truly native. It has been known for some forty years. Although not recorded by Druce, it could easily have been overlooked and it has probably been at its present site for a century or more. Identification The fronds are narrow, delicate, and small (no more than 25cm) and the pinnae well separated. Notable sites Only one currently known, on the walls of Great Missenden Parish Church, where a very small number of plants are protected by railings in a very shady and wet spot, exactly where it was first recorded in 1975 by Ted Byrne. It still grows with hart's-tongue and male fern as noted by Mr Byrne, but the hart's-tongue is spreading vigorously and could out-compete the Cystopteris. BMERC records also include a 1980 record by Ted Byrne from nearby Missenden Abbey. While there is suitable habitat there it has not been found subsequently and it is almost certain that the second record was misallocated on being entered into the records, as Mr Byrne's own notebooks in my possession make no mention of a second site, although he made several subsequent visits to the first site. He did, however, record it in 1979 on the north-facing wall of Holy Trinity Church in Penn Street (just outside our area), from which it was subsequently lost through cleaning operations. (Rustyback was lost from this site in the same way.) The fact that it existed at another site adds some evidence for its being native. Mines Our plants host the fly Chirosia histricina, which also occurs on our commoner ferns. Derivation The "bladders" are the minute bottle-shaped spore-covers on the underside of fertile fronds, which are soon lost, however, leaving the spore-heaps bare. The stalks are brittle, but this should not be tested, and indeed the plants should not be touched at all, due to their rarity.

11 Family: Blechnaceae Hard fern Blechnum spicant Another rarity in our area, hard fern is distinctive with its contrasting fertile and infertile fronds and is restricted to acid soils. Druce (1926) describes it as local to absent in our area, avoiding lime. Identification The fronds are narrow and 1-pinnate with simple short pinnae. The infertile fronds, rather like a long narrow polypody (see below), grow in a rosette and soon spread close to the ground. The fertile fronds have very narrow pinnae, dark stalks, and stand upright in the centre of the rosette. Notable sites It has been recorded in just three woodlands in our area, but still survives at all of them. It is in smallish quantity on wet clay in Monkton Wood and Hampden Common (under conifers), but is quite prolific in parts of Sandwich Wood, where it grows on drier sandy soil. Ecological associates None known. Human associations None. Derivation The fronds are stiff and "hard" to the touch. Hard fern (2 fertile fronds) in Sandwich Wood Family: Dryopteridaceae Male fern Dryopteris filix-mas Our commonest woodland fern throughout all our woodlands and sometimes walls etc. Identification Robust narrow-ovate bipinnate fronds can stand well over a metre high, often in a shuttlecock-like rosette. The pinnae are green where they meet the main stalk, which is covered, especially towards the base, by pale brown scales, which can be quite dense and obvious in young fronds. Notable sites This fern is so common in woods of all types (wet or dry) that no particular site stands out. Galls The two species noted on lady fern above also apply to male fern. There is also a fungus that can cause thick yellow blotches, but that has not yet been recorded locally. Mines The fly Chirosia histricina and the moth Psychoides filicivora cause mines and have been recorded locally. Other ecological associates The plant hopper Eupteryx filicum has been recorded on male fern in Lodge Wood. Larvae using male fern include Small angle-shades moth and two sawflies Aneugmenus coronatus and Strongylogaster lineata. The number of feeders on ferns is limited by the toughness of the leaves. Human associations I have not come across any. Derivation "Male" in distinction to the smaller, less robust "lady" fern (see above). Luxurious growth of woodland male ferns Kidney-shaped spore clusters on male fern

12 Broad buckler-fern Dryopteris dilatata Almost as common as male fern in our woodlands, and just as widely distributed. Identification Can be as large as male fern, but easily told by the tripinnate triangular frond. The scales on the stem have a narrow or wide black central stripe, often making the stalks look black from a distance. Notable sites As with male fern, this species is so common that it can be found in any woodland. Ecological associates As for male fern. Derivation A "buckler" is a small round shield, and refers to the rounded spore-coverings (see picture of male fern pinna above). The same reference occurs in the name "shield-fern" (see below) Broad buckler-fern (lower) and male fern (upper) Young cluster of broad buckler-fern Rolled shoot-tips on broad buckler-fern caused by fly Chirosia betuleti

13 Borrer's male fern Dryopteris borreri This fern used until very recently to be classed as a sub-species of Dryopteris affinis. Older records often do not distinguish the sub-species and are therefore difficult to evaluate. Dryopteris affinis, however, is very rare in our region and it is likely that all plants in our area are borreri. Identification Like male fern but with shaggier stalks, the scales being a richer golden or reddish brown. The stalk at the base of each pinna, where it meets to main midrib of the frond, has a more or less conspicuous black spot, a useful indicator because male ferns can vary in the density of their scales. These attributes are shared with affinis, but it is distinguished from that species by the pinnules, especially those of the lower pinnae, being more squared off at the end rather than evenly rounded, while the lowest pinnule on the lower pinnae has a marked lobe. It also has gradually tapering pinnae, while those of affinis have equal-length pinnules in the basal half. Borrer's male fern is intermediate between male fern and affinis in the density of scales, being less readily picked out by this character. It is a brighter green than male ferns of similar age but not shiny like affinis. Notable sites Recent records from Hampdenleaf, Hatches, Angling Spring and Monkton Woods, and from Grubbins Plantation, Little Kingshill. Older records from the edge of Peterley Wood and Seerhill Plantation. Ecological associates Probably the same as male fern. Derivation William Borrer was a botanist active in the first half of the 19th century, who apparently first distinguished this variety in Devon. A man of leisure, he had a large garden and arboretum in Sussex. Young plant of Borrer's male fern showing golden scales Lower frond showing square-ended pinnules & lobed basal pinnule [Golden-scaled male fern Dryopteris affinis affinis Despite a mis-transcribed record in BMERC (a mistake for Borrer's male fern), this species has not been found in our area. I have, however, seen it in Crowellhill Wood just to the north of our area. For distinguishing features, see under Borrer's male fern. Other subspecies of Dryopteris affinis are limited to the north and west of Britain, and ssp affinis is also much commoner away from the south-east. It usually stands out because of its very shaggy stalks and midribs and shiny appearance.] Note shiny surface, rounded ends to pinnules and no lobes on basal ones

14 Narrow buckler-fern Dryopteris carthusiana There are records for this fern from 12 woodlands, but most of them are in the 1970s only. Only two sites are confirmed for the 1980s and 1990s, while only two sites exist in the current century. It likes consistently wet conditions and may well have been lost from most of its former sites because of the lowering of the water-table and drier climate in the last two to three decades. Identification From the male ferns it is told by its more dissected fronds and not forming "shuttlecock" clusters; from broad buckler fern it differs in its generally narrower frond (like male fern), paler green colour, and scales with no dark stripe. Notable sites Still present in very wet parts of Monkton Wood, where it was recorded by Ted Byrne in 1974 (then considered "scarce") and in Peterley Wood (3 plants found by Ted Byrne in 1979 and similar number present today). It still grows by two ponds on Naphill Common, just over the western boundary of our area. Ecological associates As for other Dryopteris, but none noted locally, given its rarity Soft shield-fern Polystichum setiferum Compared to our two main woodland ferns above, male and broad buckler, other species are decidedly uncommon in our area. The most frequent of them is the soft shield-fern, although it is restricted to just a few ancient woodlands and hedgebanks. It tends to prefer slightly drier spots such as woodland banks. Identification The fronds are bipinnate like male fern and can grow equally tall, although in our area they are usually rather shorter. While the pinnules of male fern are broad at their base where they join the midrib, those of the shield-ferns are more or less stalked, giving the fern a more divided look. The pinnules also have a "thumb"- like lobe at the base and their teeth are prolonged into hair-like points. Notable sites There are records from just eight sites, of which three are woods (Cross Coppice, Sandwich Wood and Angling Spring Wood), three are ancient lanes, where it occurs on shady hedgebanks (Boss, Broombarn and Greenlands Lanes), and the last two are the grounds of Missenden Abbey and the old overgrown churchyard by Great Missenden Parish Church. It is easily overlooked and it may well occur at further sites in the area. Galls Only one fungus gall has been recorded in this country, and that only in Shropshire. Mines The two Psychoides moths mentioned under hart's-tongue fern are also known to mine Polystichum and may well do so in our area, although they have not been noted specifically on soft shield-fern. Other ecological associates No other species have been recorded locally on shield-ferns, although that is not surprising given their sparsity. Derivation For the name "shield-fern" see under broad buckler fern above. "Soft" refers to the feel of the leaves and the hair-like extensions of the teeth, in distinction from hard shield-fern (below). Young soft shield-fern fronds showing the form of the pinnules More mature plant showing superficial similarity to male fern

15 Hard shield-fern Polystichum aculeatum A very rare fern in our area with just one older record, but currently known from three sites. Druce (1926) said it was "local and generally rare" in our area "nearly extirpated by commercial collectors". It is rather ironic that this species, that was removed from the countryside into gardens is now on the course of a return journey, as at least one of the current specimens is clearly a garden escape! Identification As the name suggests, this fern has leathery fronds that last well through the winter and feel distinctly stiff, as do the hair-like points on the teeth of the pinnules, which are quite bristle-like. The lower edge of the pinnule "thumb" is straight and leaves a space between it and the stalk of the pinna, easily seen when the frond is held against the light. Notable sites It has long been known from the old churchyard behind Great Missenden Parish Church and still survives there, so may be native. It also occurs nearby in the deep ditch beside Church Lane, at the boundary of old Missenden Abbey land, plentifully on the walls of Missenden Abbey gardens, and in a nearby garden. It appears native on the shady banks of Greenlands Lane, Prestwood. Lastly, a fine clump occurs in a ditch at the edge of Lodge Wood. It is frequently sold in garden centres and occurs regularly in gardens. Varieties It hybridises with soft shield ferns in areas where both are frequent (P. x bicknellii). Some local specimens so far determined as setiferum seem tougher and intermediate in pinnule characters, so the hybrid may occur in our area, perhaps from crossing with garden aculeatum. The crucial test is that the hybrid is completely sterile. Hard shield fern (Great Missenden) Underside showing spore-heaps A specimen with finely divided fronds (3-pinnate) and very scaly midrib, Lodge Wood

16 Family: Polypodiaceae (Polypodies) Common polypody Polypodium vulgare Despite its name this fern is decidedly uncommon locally. There are two records from the 1970s and one from the 1990s, at none of which sites has it been seen since, so that only one record (1982 and 2001) is recent and the species is probably extinct in the area. The older records (1970s, 1980s) are all "sensu latu", which may refer to interjectum (see below), no attempt having been made to differentiate the various species of Polypodium. Identification Polypodies are distinct with simple 1-pinnate fronds arising singly in lines from a creeping rhizome. In our area they may be found on walls or hedgebanks, but in wetter western areas often grow on mossy tree boughs or on the ground in sand-dunes. Notable sites Once recorded at Prestwood Parish church, but no specimens have been found since 2001, a victim of wall-cleaning. A clump has however escaped from a garden along Prestwood High Street and can be seen at the base of the wall beside the gate. Ecological associates Two leaf-mining flies have been reported on Polypodium in this country, but neither has been noted locally. Human associations None. Derivation "Polypody" is from the Greek for "many-footed" and either refers to the fronds growing singly from separate bases or to the series of rootlets along the rhizome. Intermediate polypody Polypodium interjectum This species grows in more calcareous areas, while common polypody usually grows in more acid or neutral substrates. It is probably the commonest polypody in the south-east and can be plentiful on limestone walls in south Oxfordshire, the Cotswolds and some other parts of the Chilterns. In our area, however, it is limited to just two sites. Identification There are three British species of polypody. Common polypody (above) has narrower fronds that are parallel-sided; southern polypody (P. australe) has very broad fronds and only grows in the west of the country (in spite of the confusing name); while the current species is intermediate in shape, widening in the middle. It is also distinct from vulgare in its two basic pinnae turned forwards out of the plane of the frond ("inflexed"), although this feature is somewhat variable in both species. Notable sites Garden wall of cottage at Stonygreen, where it has been known for over 50 years; hedgebank outside garden in Whitefield Lane, Great Missenden, where it appears to be a recent garden escape. Varieties Common and intermediate polypodies may hybridise to form P. x mantoniae. A possible specimen was reported by Alan Showler in 1989 from a grassy garden wall in Hughenden Valley. The hybrid is sterile and therefore unlikely to have survived long.

17 [Family Azollaceae] [Water fern Azolla filiculoides Our only water fern (introduced) has not so far been recorded in our area, but does occur in ponds in the wider Chilterns, where it is usually a garden throw-out. It grows vigorously and can persist a long time. In autumn its red fronds make it highly conspicuous. It often covers the whole surface of the water and prevents light reaching submerged flora and fauna.] [Family Marsileaceae] [Pillwort Pilularia globulifera A primitive fern native to marshes on old acid commons. Never recorded in our area and very rare in the Chilterns with only one known site - Nettlebed Common (discovered in 2018 by Andy McVeigh). Submerged much of the time, the long thin rhizomes put up very slender stems with curled tips (more leaf-stalks than proper leaves), at the base of which small globular fertile leaves (the "pills" of the name) develop and release spores into the mud. Pillwort, rhizome to the left, with slender curled-tipped leaves