Adderstongue Fern

Tucked away in an obscure corner of Chorlton Ees is an extraordinary little plant which it is very easy to overlook. So easy to overlook, in fact, that I suspect that when I found it in 1995 I may have been the first person to see it for nearly 140 years. Richard Buxton recorded it in his Flora of 1849 (1) and Leo Grindon in his Flora published 10 years later (2) – but I’ve not seen any later records.
The plant is Adderstongue Fern (Ophioglossum vulgatum) which is generally regarded as an indicator plant of unimproved grassland, a habitat which has declined dramatically, especially since the Second World War. Once it was accompanied by other indicator plants such as Green-winged Orchid (Anacamptis morio) and Meadow Saxifrage (Saxifraga granulata) – but these are long gone. The site itself has taken a bit of a hammering over the years. It was deliberately flooded every year by local farmers for 200 – 300 years, then it was part of Withington Sewage works (for about 70 – 80 years) followed by being regularly burned out by vandals. The Adderstongue stoically survived all this but I don’t think that it would survive much trampling – which is why I’m not going to tell you exactly where it is.

The Adderstongue is a true fern but it doesn’t look much like one. In fact it is a very ancient type of fern and ‘modern‘ferns may have evolved from something like it. According to Robbin C. Moran, Curator of Ferns at the New York Botanical Gardens (3), DNA evidence suggests that Adderstongues and their relatives are very ancient lineages but, paradoxically, they don’t appear in the fossil record until relatively recently (perhaps ancient Adderstongues didn’t fossilise well or palaeontologists just haven’t found an ancient Adderstongue fossil yet?). The more familiar ‘shuttlecock’ type ferns, like Male Fern and Broad Buckler Fern, are truly a recent group in every sense (in terms of both DNA and fossils) and first appeared in the fossil record in the late Cretaceous about 75 million years ago - which makes them younger than flowering plants, which first appeared about 140 million years ago; around 80% of modern ferns are of the ‘shuttlecock’ type.

Although many ferns may not be as ancient as is often believed their method of reproduction is primitive compared with flowering plants. The fern broadcasts spores, each of which produces an inconspicuous, green, often heart-shaped, plate-like plant called a ‘prothallus’ or ‘gametophyte’. The prothallus produces sex organs: ‘antheridia’ which produce spermatozoids, and ‘archegonia’ each of which holds one egg cell. The prothalli usually grow on a substrate which supports a film of water and the spermatozoids swim through this film until they encounter an archegonia, which they fertilise. From this union arises a new and quite different type of plant called a ‘sporophyte’. The sporophyte is what we generally recognise as a ‘fern’. The sporophyte produces spores, either from organs called ‘sori’ on the undersides of its leaves or from specialised, spore-bearing fronds, and the whole cycle starts again (4).
The picture above shows the sporophyte stage of Adderstongue Fern. The blade-like leaf at the back is sterile and the rod-like structure arising from it is the spore-bearing frond; spores are shed from horizontal slits near the top of this frond. Adderstongue prothalli are tuber-like, lack chlorophyll and develop underground. Robbin Moran says that, “Little is known about subterranean prothalli; they are rarely seen”. But it is known that they have embedded in their tissues a symbiotic fungus that absorbs nutrients from the soil and translocates them to the plant (5). The sporophyte stage of the plant usually has an underground rootstock with creeping stolons which can often produce new plants at intervals. In this way Adderstongue can often produce extensive colonies (6) – as on Chorlton Ees. The rootstocks and stolons are also ‘infected’ with the symbiotic fungus (7).

Adderstongue Ferns have been used in herbal remedies for centuries. The 17th Century herbalist, John Gerard prepared ointments for treating skin complaints from the British species and Asian species are still used in modern Chinese medicine (8). A word of warning, though; preparation, form of application and dosage may be critical. One of Britain’s leading fern experts, Dr Christopher Page on learning that the plant was supposed to have a sweet taste, and is palatable to cattle and rabbits tried nibbling on a frond. He reported (9) that, “ ... a specimen experimentally eaten by the author caused swelling of the tongue, and this is not recommended.” You have been warned!

Dave Bishop, May 2009

References:

1. ‘A Botanical Guide to the Flowering Plants, Ferns, Mosses and Algae Found Indigenous Within Sixteen Miles of Manchester’ by Richard Buxton, Longman, 1849.

2. ‘The Manchester Flora’ by Leo Grindon, William White, 1859.

3. ‘A Natural History of Ferns’ by Robbin C. Moran, Timber Press, 2004.

4. ‘The Illustrated Field Guide to Ferns and Allied Plants of the British Isles’ by Clive Jermy and Josephine Camus, Natural History Museum Publications, 1991.

5. Moran

6. Jermy and Camus

7. Moran

8. Moran

9. 'The Ferns of Britain and Ireland’ by C.N. Page, Cambridge University Press, 1982.