Ferns in Suffolk

FERNS IN

SUFFOLK

T h e ferns, or Filicinae, belong to the ancient plant order of Pteridophyta, classes of which have survived from Palaeozoic times.

Unlike the flowering plant, the adult fern produces no seeds as s u c h ; instead, thousands of minute, one-celled spores form inside spore-cases—sporangia. T h e life history of the ferns has two distinct phases. It begins with the liberation of the spores from the sporangia Clusters, or sori. Given conditions of warmth and sustained dampness, the wall of the spore splits, and the cell develops into a flat, green, heart-shaped body called prothallus, which contains Chlorophyll and which is an individual plant.

It is on the underside of these prothalli that are formed the male and female gametes—the antheridia and the archegonia—which correspond to the anthers and style of the flowering plant*. T h e first phase of the life history—the gametophyte—ends with the fusing of the two organs to form a Zygote.

T h e second stage—the sporophyte—begins with the Zygote and culminates in the production of the spores by the adult fern.

As soon as the Zygote is formed, the fronds proper appear, the first being very simple, but subsequent ones becoming rapidly more complex until the adult fern is attained. Some young ferns, for example the Male Fern (Dryopteris filix-mas), take only two seasons to become identifiable, but others, with bi- or tri-pinnate fronds are slower and often cause trouble in identification until they are mature, when the arrangement and type of sorus with its covering, or indusium, can be examined.

In the British Isles there are six families of Filicinae, comprising some forty-five species. This number, however, is not conclusive as there is still doubt as to the specific or sub-specific status of some ferns. Suffolk is not generally regarded as fern country, as the relatively dry climate makes suitable habitats scarce.

However, the country possesses about half the ferns on the British list.

T w o species of the family Ophioglossaceae are to be found in Suffolk, the Adder's Tongue (Ophioglossum vulgatum) and the Moonwort (Botrychium lunaria). These two plants are often passed by, unnoticed beneath higher Vegetation, and even if discovered are frequently not recognised as ferns at all. T h e Adder's Tongue consists of a single, ovate, plantain-like, barren frond, with the simple, fertile, spike branching out from the top of the stalk. T h e Moonwort, also, has one barren frond although it bears its sporangia on a bi-pinnate stalk. T h e barren frond is divided into fleshy, fan-shaped pinnae.

This fern is said to * T h i s is the general form of prothallus. Exceptions among Suffolk ferns are the Ophioglossaceae, whose prothalli are subterranean, and Azolla filiculoides which produces separate male and female prothalli from microspores and megaspores respectively.

256 FERNS IN SUFFOLK be frequent in rabbit-free enclosures on the Breckland. In some parts of the country the decrease in the numbers of these animals through myxomatosis has resulted in an increase of the plant, and this may be so in Suffolk.

The ferns of the family Osmundaceae are of primitive type ; fossilised stems, stocks and sporangia of the Permian and Carboniferous Ages, but similar to those of present-day species, have been discovered. Osmunda regalis, the Royal Fern, rare in Suff has been eradicated from some old haunts by the draining of marshes and by unrestricted collecting. The leathery, bi-pinnate fronds sometimes rise to seven feet and the topmost pinnae are completely covered with sporangia, giving the fern a dock-like crest: hence its old name of " Flowering Fern "—a contradiction in terms.

The family Polypodiaceae comprises at least 85 % of the recorded ferns of modern times. The Bracken (Pteridium aquilinum) is the sole British representative of the sub-family Pteridoideae, and is by far the commonest fern in the British Isles, thriving despite drastic measures taken by farmers to destroy it. On dry heaths it spreads by means of long underground rhizomes, and it had been suggested that its spores no longer function ; but by what other means than by wind-borne spores did Bracken propagate on bombed-sites ?

The pale green rosettes of the Hard Fern (Blechnum spicant) occur on some damp heaths and locally alongthemargins of woods.

This is another species whose fertile fronds are distinct, for whilst the lanceolate, barren fronds lieflat,these stand up vertically with the linear sori causing the pinnae to curl.

Included in the sub-family Asplenioideae are the Hartstongue, the Spleenworts, the Rusty Back and the Lady Ferns. The Hart's-tongue (Phyllitis scolopendrium) is widespread, but as it likes damp and shade its favourite habitats are sides of wells and drains—even in central Ipswich. Near Middleton Moor, however, it grows in the open hedge-bank in the best Devonshire fashion ! The frond is strip-like, with paired linear sori which, • when ripe, form brown lines on the backs of the fronds.

Three of the eight British Spleenworts occur in Suffolk. They are capable of withstanding drought and would probably be much commoner if it were not for the lack of suitable habitats due to the predominance of brick construction in the county As it is they are mostly confined to churches and stone bridges There are, höwever, several West Suffolk vilages built largely of stone, on whose walls they grow, the tufted Wall Rue (Asplenium rutamuraria) in particular being common. The numerous fronds of this fern, rarely longer than two inches, are divided into stalked, wedge-shaped segments. The frond of the Maidenhair Spleenwort (A. trichomanes) has a long dark rachis with small green pinn In winter these pinnae drop off, leaving the bare brown stems

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hanging in a tuft. The backs of both trichomanes and rutamuraria are often covered completely, in late summer, with ripe brown sporangia. A. adiantum-nigrum, the Black Spleenwort, has a triangular glossy frond, which, although often tri-pinnate at the base, quickly becomes simpler towards the apex. Suffolk specimens aie mostly stunted, the majority growing on walls. I have never found them here growing in a hedgebank, a habitat which in the West Country produces the finest specimens.

The Rusty Back (Ceterach officinarum), similar in habit to the Spleenworts, is even more local in Suffolk than they. The short, yellowish-green frond is deeply pinnatifid and, since the pinnae are sub-opposite, has the appearance of rick-rack braid. The backs of the pinnae are totally covered with overlapping tawny scales, which give the fern its name. In prolonged dry weather the fronds curl up, appearing shrivelled and dead, although they quickly expand with the return of moisture.

The delicate, drooping Lady Fern (Athyrium filix-femina), although growing in perpetually damp leaf-mould in woods and carrs, in Suffolk seldom attains the luxuriant growth so typical of specimens in the Western Counties. Perhaps to do so requires moist air as well as damp soil. It is one of the most variable ferns, not only in growth but also in the forms of sorus, which ränge from horseshoe-shaped to linear on the same frond.

The main distinguishing feature of the Dryopterids, or Buckler Ferns, is the kidney-shaped indusium covering the sorus. The most common species is the Male Fern (Dryopteris filix-mas) whose " shuttlecocks " of large lanceolate fronds grow in many woods. Another fern, D. borreri, until recently thought to be only a variety of filix-mas, is probably often passed by as just another rather sturdy specimen of that species. In borreri the smaller sori, the golden-brown scales densely clothing the stipes and rachis, the dark patch at the base of the pinnae, and the rather square-ended pinnules distinguish it from the Male Fern.

The similar bi- or tri-pinnate growth of the Broad and Narrow Buckler Ferns (D. austriaca and D. spinulosa) makes these two ferns often difficult to teil apart, although the pinnae of spinulosa are shorter and wider spaced. However, the scales on the stipes of austriaca, having a dark line through them, distinguish this species from the Narrow Buckler whose scales are uniformly tawny.

Both ferns are common in damp woods, and well-grown specimens can be found, often growing on stumps of trees. There is a third similar species, D. aemula, the Hay-Scented Buckler, which has up-curved pinnules, and was recorded for Suffolk in the last Century.

In having on its list the Crested Buckler (D. cristata), Suffolk has the enviable distinction of possessing one of about six species that even Wales, so rieh in ferns, does not record. It is a rare

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marsh fern, whose East Anglian habitats are some of its last strongholds. It occurs in a few damp carrs and in some littleknown marshes. T h e fronds are long and narrow, with triangular pinnae divided into large pinnatifid pinnules.

T w o of the Shield Ferns grow in Suffolk, the Hard (Polystichum aculeatum) and the Soft (P. setiferum). T h e sori and indusia are circular, and both species have bi-pinnate fronds with sharplytoothed pinnules. T h e fronds of the Hard Shield Fern stand erect, whilst those of setiferum, being softer and smaller, droop. Both ferns are widespread, but like the Suffolk species except the Bracken, and locally the Male Fern, are not abundant.

One Thelypterid, the Marsh Fern (Thelypteris palustris) is definitely reported from Suffolk, and the Mountain Fern (T. oreopteris) was recorded in the last Century and may still exist.

T. palustris, found locally in wet boggy marshes, is one of the few species that tolerate having their roots actually in water. Where it does occur, it forms large patches, with the underground rhizomes sending up single frail fronds. It is the predominant fern of the Norfolk Broads. T h e Mountain Fern resembles Dryopteris filix-mas, but its pinnae dwindle right down to the stock, leaving no stalk, and the small sori are arranged around the margins of the pinnules, instead of near the midrib.

T h e Common Polypody (Polypodium vulgare) is perhaps the most drought-resistant of the British species. It grows on dry banks, wall tops, and tree trunks, appearing fresh when even some of the Spleenworts are wilting. T h e fronds, which arise singly from a creeping rootstock, are pinnatifid, dull green and of a leathery texture, with the circular, naked, yellow sori situated in rows on the backs of the long pinnae.

T h e last Suffolk fern to be described belongs to the family Azollaceae. This species, Azolla filiculoides, a water fern, native of tropical America, was introduced into this country at the end of the last Century. It floats on the surface of still water in the manner of duckweeds. It would seem to be susceptible to frosts as it has perfected the art of disappearing completely from habitats where it was recently abundant. Spores of a species of Azolla have been found in interglacial deposits at Hoxne.* DĂźring this Century the pteridological kleptomania that had previously reigned, has lapsed, much to the benefit of the ferns, many of which had been grubbed up regardless of their numbers, only to perish in the often unsuitable surroundings of a fern house.

T h e taking of one or two fronds, however, does no harm to the fern, causes no detriment to the countryside and provides ample material for fern propagation from spores. Much pleasure can be derived in this way from the study of the Filicinae in all the stages of their life history.

BEAUFOY. A N N E •Transactions, S . N . S . Vol. V I I I , pt. II

p. 61.

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Bibliography.

Clapham, A. R., Tutin, T. G. and Warburg, E. F. (1952).

Flora of the British Isles. London.

Hind, W. M. (1889). The Flora of Suffolk. London.

Hyde, H. A. and Wade, A. E. (1954). Welsh Ferns. Cardiff.

Step, E. (1949). Wayside and Woodland Ferns. London.

Turrill, W. B. (1948). British Plant Life. London.

SANDCOVERT MARSHES, BLYTHBURGH, ii Since an account of these marshes appeared in Vol. ix, Pt. 1, 1954, there has been a further setback in the progress towards reclamation, for the high tides of 22nd December, 1954 again breached the wall and the marsh was flooded with sea water which remained for a fortnight. The result on the growth of flora has, however, been interesting.

In the summer of 1954, the ground cover was sparse with large expanses of bare soil and a limitation in plant species. Soil conditions are now rather unusual. Up to September, 1955 no attempts had been made at drainage, other than the excavating of a new delph ditch inside the river wall. The old ditches are almost fĂźll of silt, but allow for about 1' of spring water which finds its way from Spring Hill on the north side of the main road.

Along the length of these filled ditches, a great variety of flora has established itself in a condition of slowly moving fresh water in a moist soil of high salinity. Away from the ditches, the surface soil has deeply cracked into a mosaic pattem, whilst the sodium chloride in the soil was very high. In August, when final observations were made, the upper 3" of soil was dry and the salt content of the first 6" of soil was 2.25%, whilst at the same time in 1954 it was 1.62%. The net volume of salt in August, 1955, in 6" of soil was 18 tons per acre which by comparison with a salt application for sugar beet is seventy-two times the maximum amount applied per acre.

The main cover of the marsh is made up of Suaeda maritima and Salicornia stricta, whilst Aster tripolium is evident all over the marsh. The growth habit of Aster tripolium is interesting, for there is great Variation in its height and the number of the flowering stems ; in height it ranges from 6" - 5', whilst some single plants have 45 - 50 flowering stems. On August 4th there