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
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
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 1974. 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 1977. 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).
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
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.
Field horsetail
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 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 10-30 ridges, and pale green sheaths with small whiteedged black teeth.]
Rough horsetail in garden pond, Orchard Lane
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
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
2013-14).
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".
10.7
Wall-rue typically growing on railway bridge brickwork
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 bridge at the bottom of Whitefield Lane (2007,
but not there 2014), 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").
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.
Young leaves of wall-rue are less divided
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.
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.
Mines Our plants host the fly Chirosia histricina, which also occurs on our commoner ferns.
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.
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.
Family: Blechnaceae
10.10
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
Broad buckler-fern Dryopteris dilatata
10.11
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
10.12
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
10.13
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
Hard shield-fern Polystichum aculeatum
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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. The last
site in Lodge Wood is at the boundary of a garden and obviously constitutes an escape. 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
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.
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[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.]
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