Polypodium vulgare L. agg., Polypody
Account Summary
Native, common, widespread and locally abundant. European boreo-temperate.
1860; Smith, Rev Prof R.W.; Brookeborough.
Throughout the year.
Taxonomy
What was for many years treated as one Polypodium species in B & I has been recognised, since 1960, as a polyploid complex of two rhizomatous perennial species (tetraploid Polypodium vulgare and diploid P. cambricum (Southern Polypody)) and the fertile allopolyploid hybrid between them (hexaploid P. interjectum (Intermediate Polypody)) (Shivas 1962; Jermy & Camus 1991). Some forms of Polypody require microscopic investigation to identify with certainty and, therefore, field records are still very frequently made at species aggregate level (ie as P. vulgare agg. or s.l.), and the constituent species and hybrids seem destined to remain under-recorded.
Growth form and preferred habitats
All forms of Polypodium, like Bracken, do not develop a crown, but instead possess a scaly, creeping rhizome, which in this case runs along the surface of the ground rather than being buried in the soil. From the rhizome, leathery, evergreen, hairless, aerial fronds resistant to both frost and drought arise at intervals, generally only a few centimetres apart. Fronds vary enormously in length from just a few centimetres in stunted forms growing in dry or exposed situations as in rock crevices or on walls, but they can develop up to 45 cm in length in the case of hybrids which display 'hybrid vigour' or heterosis.
Representatives of the Polypodium vulgare agg. typically grow amongst mosses and leaf-mould on semi-shaded rock outcrops, under hedges, on walls, on roots and stumps of trees, or on the trunks and thicker branches of mature trees in damp woods.
Reproduction
The sporing sori are formed in pairs on the underside of the herringbone-like frond either side of the stalk (technically called a 'rhachis') in the upper one to two thirds of its length. The sori are large, rounded, naked of any covering indusium tissue and are a conspicuous, golden-orange colour when fully developed, anytime between June to September. The sporangia are so securely attached that indentations appear on the upper side of the frond opposite the sori positions beneath.
Fermanagh occurrence
In Fermanagh, P. vulgare s.l. is very common and widespread, having been recorded in 401 tetrads, 76% of those in the VC. The species aggregate typically grows amongst mosses and leaf-mould on semi-shaded rock outcrops, under hedges, on walls, on roots and stumps of trees, or on the trunks and thicker branches of mature trees in damp woods.
British and Irish occurrence
The New Atlas hectad map shows P. vulgare s.l. occurring throughout the vast majority of B & I, but absent from the Channel Isles and less prevalent in the English Midlands and up the E coast from the Wash to Newcastle-upon-Tyne. The New Atlas map also indicates areas of less common occurrence or absence over parts of the Irish Midland plain, and also in the more exposed, wet, nutrient-starved, boggy ground of Cos Clare (H9), Roscommon (H25), W Mayo (H27) and W Donegal (H35).
World occurrence
On a European basis, the aggregate species occurs widely and commonly throughout continental Europe extending from Gibraltar and Crete in the south, to the northern tip of Norway, Iceland and the southern tip of Greenland, but absent from Jan Mayen and the Arctic Islands (Svalbard, etc.) (Jalas & Suominen 1972). Eastwards, P. vulgare agg. occurs in the Caucasus, Urals, the Himalaya, and, in an even broader definition (P. vulgare sens. lat.), it becomes circumpolar and stretches around middle latitudes of E Asia and across northern and central regions of N America (Hultén 1962; Hultén & Fries (1986, Map 74).
Medicinal uses
The rhizome of Polypodium had several uses in herbal medicine and was often referred to as Polypody of the Oak, or Oak fern (not our modern, much more delicate Gymnocarpium dryopteris). There was a belief that ferns and flowering plants that grew on oak roots or branches were especially efficacious as remedies. Its principal use was as a mild laxative, but it was also considered useful for coughs and catarrh. An infusion made from the crushed rhizome was drunk like tea as a treatment for the early stages of consumption or for rheumatism. Polypody was used to treat jaundice, dropsy, scurvy and other skin complaints, and dried powdered rhizome used alone or mixed with honey was also said to remove nasal polyps (Grieve 1931; Vickery 1985).
Names
The genus name 'Polypodium' is Latin but is derived from two Greek words 'polus' meaning 'many' and 'pous' meaning 'a foot', the notion being either that the plant having a branched rhizome has many feet (Grigson 1974), or more likely, that the comb-like, pectinate frond resembles a centipede (Prior 1879).
In addition to the English common names mentioned above, this easily recognised and well-known fern aggregate has been given at least nine other names including: 'Brake of the Wall', 'Adder's-fern', 'Everferne', 'Wall Fern', 'Wood Fern', 'Golden Locks', 'Golden Maiden-hair', 'Golden Polypody' and 'Moss Fern'. The latter, a name proposed by Gerard (1597), is rather apt (Britten & Holland 1886).
Threats
None.