Members Reports and Photos
PRAEGER CENTRE, national botanic gardens, 4th October 2014
LEADER: DECLAN DOOGUE
Ferns in Autumn
Following on from our meeting earlier this year, we re-visited basic fern identification but will and examined a number of difficult pairs such as Dryopteris affinis / D. filix-mas and Polystichum setiferum / P. aculeatum; as well as a number of potential hybrids.
The morning session was devoted to Horsetails and specimens of Equisetum arvense, E. fluviatile, E. hyemale, E. palustre and E. sylvaticum were available for examination - both dried and fresh material. Cross-section of stems and leaves and the sheaths were examined using handlenses. Particular attention were given to E. hyemale and its hybrids E. x trachydon and E. x moorei. E. x moorei is found in Ireland on coastal sand dunes in Wicklow and Wexford only and is named after David Moore formerly of the NBG. Its parents are E. hyemale (Dutch Rush, formerly Shave-grass) and E. ramosissimum. The absence of the latter parent in Ireland (and the existence of only a couple of sites in Britain) has given rise to some speculation about its origin, but see below. Is it a relict hyrbid or was it introduced by human activity and then spread vegetatively along the Wicklow-Wexford coast? E. hyemale is scarce with a scattered distribution in Ireland? E. hyemale, because of its high silica content and the fine teeth on its ste, was once used for scouring pans, burnishing brass and for sand-papering the insides of some wood (musical) instruments. E. x trachydon (Mackay's Horsetail after the celebrate botanist who worked in Ireland) whose parents are E. hyemale and E. variegatum is also a scarce species with a scattered distribution. The most common hybrid horsetail is E. litorale, a hybrid between E. arvense and E. fluviatile, and is quite easily recognised early in the season by its short whorls of branches on its stem. E. limosum now considered to be an unbranched form of E. fluviatile was once known as Water Pipes!
Recently a new hybrid Horsetail Equisetum x meridionale (E. ramosissimum x E. variegatum) has been recognised in Britain and some of the plants identified there as E. x trachydon have turned out to be this 'new' hybrid. (P. Jepson et al. 2013 New Journal of Botany 3(1):24-33). Electon microscopy has been used in confirming its identity. This raises interesting questions relating to its possible occurrence in Ireland.
One participant brought along a horsetail purchased in a garden centre. It was labelled Equisetum japonicum aka Equisetum ramosissimum. Further research has gleaned that there is a practice in the horticultural trade of using this nomenclature for E. hyemale. Declan's production of specimens of Rosa agrestis from Lough Ree made for continuity with the previous month's Praeger workshop ...
In the afternoon we looked at or discussed a range of ferns and some hybrid-like material: Asplenium adiantum-nigrum, A. ruta-muraria, A. trichomanes, A.(Phyllitis) scolopendrium, Athyrium filix-femina, Blechnum spicant, Ceterach officinarum, Dryopteris affinis agg., D. carthusiana, D. dilatata, D. filix-mas, D. oreades, Oreopteris limbosperma, Polypodium cambricum, P. interjectum, P. vulgare, P. aculeatum, P. setiferum, P. x bicknelli and Pteridium aquilinum. Clearly the Dryopteris affinis group requires much more attention and members are also encouraged to look out for potential hybrid-type material in the Polypodium and Polystichum genera.
Those attending agreed the this Praeger session reached an even higher level with regard to presentation, interest and stimulation.
For those interested in further study of Horsetails, Ferns and related groups then the second edition of the monograph The Ferns of Britain and Ireland by C.N. Page is essential reading and an invaluable reference source. Ken Trewren's Field Guide to the Dryopteris affinis complex is the latest available for this challenging group. Other excellent publication include James Merryweather’s The Fern Guide (AIDGAP Field Studies Council) and his Key to Common Ferns (also FSC). Another useful resource is the Plant Crib which is to be found on the BSBI website bsbi.org.uk.
E. hyemale E. hyemale E. x trachydon
E. x moorei E. variegatum E. telmateia
E. sylvaticum E. arvense E. fluviatile
E. palustre E. palustre var. polystachion
Equisetum hybridisation E. x litorale
Dryopteris carthusiana D. oreades
D. affinis / borreri Oreopteris limbosperma
Photographs © P. Lenihan
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