EVENTS

Members Reports and Photos

SATURDAY 3 MAY  2014            

LEADERs: DECLAN DOOGUE AND pAT LENIHAN

PRAEGER CENTRE NATIONAL BOTANIC GARDENS

 An Introduction to the Identification of Ferns and Fern Allies

In the morning session, Declan made good use of aids both old and new to introduce us to the identification of ferns and horsetails and provided an impressive quantity of fresh and curated specimens.

John E Sowerby’s superb illustrations in A supplement to ferns of Great Britain and J E Smyth’s English Botany Vol VIII were produced from Declan’s library. Despite newer methods of printing and reproduction these have not been surpassed in their capture of the salient details of our native ferns and horsetails.

The more modern publications by James Merryweather’s  - The Fern Guide (AIDGAP Field Studies Council) and his Key to Common Ferns (FSC) - were available for purchase. Another useful resource was the Plant Crib which is to be found on the BSBI website.

As a first step horsetails may be simply classified as:

1.  Having both fertile (with cones) and non-fertile (without cones) stems e.g. Equisetum
 telmateia and E. arvense. These species are termed dimorphic.

2.  All stems the same e.g. E. sylvaticum.

3.  Stems with cones but no branches e.g. E. hyemale.

With lenses we looked at cross-sections cut with a razor blade and noted that E. telmateia branches have a five-sided x-section,  E. arvense 4-sided and E. sylvaticum 3-sided.

We examined one of the rarer horsetails in Ireland  the Dutch Rush E. hyemale which is normally unbranched and its rough surface contains silica was once used to clean pipes and scours domestic pots and pans before the advent of “brillo pads”.  

Mackay’s Horsetail E. x trachydon (E. hyemale x E. variegatum) is more plentiful in Ireland than elsewhere due to our moist climate which facilitates hybridisation. Then then there is E. x moorei (E. hyemale x E. ramosissimum) which is found on the Wicklow/Wexford coast, but E. ramosissimum is unknown from Ireland and Britain!  E. wilmottii (E. fluviatile x E. telmateia) has been discovered at Dowra in Co Cavan.  Clearly there is much work still to be done on the status and distribution of horsetails in Ireland.

We were given an overview of the Polypodia by Declan . Three species occur in Ireland E. vulgare with its long parallel-sided frond typically found on acid walls. E. interjectum is ‘leathery’ and typical of limestone habitat and E. cambricum (australe) with its pointed pinnules and second last pair protruding is typically found on estate walls. So the question arises as to whether the latter is native or has been introduced /escaped from cultivation.  The hybrids P. cambricum x P. vulgaris and P. cambricum x P. interjectum should be looked for.  Determination of the identity of some specimens and of hybrids requires microscopic examination of the sporangia.

Several of our native ferns are dimorphic - Blechnum spicant, Osmunda regalis, Ophioglossum vulgare and Botrychium lunaria - having both fertile and non-fertile fronds. B. spicant with its strap-like leaves is quite common and the Royal Fern is found in acidic wetland habitat.

The Dryopteris group which might loosely be described as the shuttlecock ferns from the emerging form of the young fronds may be bipinnate or tripinnate and the colour and markings of the stem scales are useful features in identification.  Three common members of this group are D. dilatata (very widespread) with its triangular shaped frond, D. carthusiana (wet woodland and lowland fen) which is almost parallel-sided and D. aemula (acid woodland) which has a very crinkled appearance. With a little experience the Male-ferns Dryopteris filix-mas and “D. affinis” can  be readily separated notably by the dark mark at the junction of the pinnae and rachis (stem). The members of the affinis group are much more difficult to differentiate and K Trewren has recently produced a Field guide  Some taxa within the Dryopteris affinis group.

There are three members of the Shield Ferns Polystichum genus within Ireland.  P. setiferum is quite common, P. aculeatum is less plentiful and P. lonchitis is quite rare but seen by Field Club members in Co Fermanagh in 2013.  There is also evidence of hybridisation within this group.

Clubmosses and Upland Ferns

The afternoon session was led by Pat. Upland ferns and lycophytes were the subjects for consideration. Specimens of Hymenophyllum wilsonii were examined and the features that differentiate it from H. tunbridgense, the other member of the genus that occurs in Ireland, were identified. This was followed by an introduction to lycophytes (attached) after which participants were given the opportunity to study samples of H. selago, L. clavatum, D. alpinum, and S. selaginoides. The session concluded with a slide show, which included images of less frequently encountered ferns such as Asplenium viride, Polystichum lonchitis and Phegopteris connectilis. Finally, the event was closed by Declan who led a visit to the Fern House, which was opened specially for the occasion courtesy of the Gardens’ management and staff.

David Nash & Pat Lenihan

       

Fern Allies...             Dryopteris affinis agg.             English Botany

           

Equisetum arvense          E. moorei                     E. sylvaticum         E. palustre

     

E. telmateia                          E. telmateia

  

       

Polypodium cambricum         P. interjectum                     P. vulgare

         

Lycopodium selago          L. clavatum                      L. selaginoides

     

Diphasiastrum alpinum                                                                       Huperzia selago

         

Selaginella selaginoides    S. kraussiana                                               Lycopodium clavatum

     

Trichomanes speciosum      Hymenophyllum wilsonii

    Photographs © Pat Lenihan

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