THE NATIONAL HERBARIUM

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 THE ROLE OF THE NATIONAL HERBARIUM

 The National Herbarium at Glasnevin contains a collection of more than half a million dried and documented plant specimens from Ireland and the rest of the world. The collections and associated literature and documentation act as a central repository of information relating to the distribution and taxonomy of the flora of Ireland.
The museum collection contains some 20,000 samples of plant products, including fruits, seeds, wood, fibres, plant extracts and artefacts.
The herbarium serves as a reference centre, a documentation facility, a data storehouse and a research institution for the study of Irish and international botany.
Associated with the herbarium is a library with extensive archives relating to the history of horticulture in Ireland, and the flora of Ireland.

HISTORY OF THE NATIONAL HERBARIUM

The Botanic Gardens were established in 1795 by the Dublin Society and passed into State control in 1877. They are currently administered by the Department of Environment and Local Government, under the auspices of Dúchas, the Heritage Service. The herbarium (code DBN in Index Herbariorum) was founded in 1847, and was formerly at the National Museum of Ireland, Kildare Street, Dublin. In 1970 the herbarium was transferred to the Botanic Gardens, and amalgamated with the smaller Garden’s herbarium (DUB). At the same time, the museum of economic botany, also founded by the Dublin Society, was transferred to the National Botanic Gardens from the National Museum.

RESEARCH IN THE NATIONAL HERBARIUM

Research in the herbarium includes work on the distribution and taxonomy of the Irish flora and the flora of south-east Asia. As well as providing an identification service to the Botanic Gardens, and the public, the herbarium also produces several publications each year. These include the journals Glasra, Contributions from the National Botanic Gardens, Glasnevin, and Occasional Papers. These journals are distributed in exchange for journals from museums and Botanic Gardens around the world.

TAXONOMY

One of the primary activities of taxonomy is the naming of new taxa as well as the remodelling of old taxa. Frequently upon further study it is determined that some taxa must be remodelled, i.e. divided, united, transferred, or changed in rank
  • Divided — make two taxa out of one.
  • United — combine two or more taxa into one.
  • Transferred — decide that one taxon belongs in another, e.g. a species belongs in another genus.
  • Changed in rank - e.g. make a subspecies a species or vice versa.
Plant groups need to be revised periodically because of several factors:
  • Previously unknown species are still being collected in underexplored areas.
  • Experimental results (Pollination biology, breeding experiments) reveal previously unrecognised differences or similarities.
  • New ways of analysing specimens become available (SEM, Molecular systematics, DNA)
  • New methodologies for analysing data (Numerical analyses, Cladistics).

NAMING PLANTS

Naming plants comprises two quite separate processes:
  • 1. CLASSIFICATION:
    the process of deciding what the taxa are, and how they might be related to one another.
    All individual organisms should, with a few exceptions, belong to one species or another — The definition of what a species is, however, is at the same time, both the simplest and most philosophically contentious issue in biology.
  • 2. NOMENCLATURE:
    the process of deciding what name applies to a taxon.
    Many species have been described on more than one occasion, while for other ‘species’ it can be found that what was formerly regarded as one taxon may consist of two or more species — which name is the correct name is governed by a set of rules.
The naming of plants is governed by a set of rules, the International Code of Botanical Nomenclature (ICBN). The code comprises six main principles (with 62 Articles and many Recommendations), which govern the process of plant nomenclature.
    1. Botanical nomenclature is independent of zoological nomenclature.
    2. The application of names of taxonomic groups is determined by means of nomenclatural TYPES.
    3. The nomenclature of a taxon is based upon priority of publication.
    4. Each taxon can have only one correct name.
    5. Scientific names of taxonomic groups are treated as Latin regardless of their derivation.
    6. The rules of nomenclature are retroactive unless expressly limited.

TYPE SPECIMENS

Within a herbarium there are a number of specimens in folders with bright red margins, and often prominently labelled ‘Type’. These are very important specimens in regard to the application of plant names.
Every species of plant is based on a Type specimen. This specimen is neither a ‘perfect’ example nor an ‘average’ example of the species, but simply a ‘typical’ member of it.
The type of a species or sub-species is a single herbarium specimen but there may be duplicates.

WHY HAVE TYPES ?

Suppose many years after a species has first been recognised, it is discovered that in reality there are two species, only recognised when a previously overlooked character is studied. The type specimen of the first species must belong to one or other of these 2 species (determined by checking the new diagnostic character), and therefore the taxon without a name is readily determined. This ensures that a name is fixed to a particular species, and is not open to interpretation.

AN EXAMPLE OF A NEW IRISH SUB-SPECIES

When a species or sub-species is first described, in this case Luzula multiflora subsp. hibernica, it has to be published, and this publication has to fulfil certain criteria to be valid:
  • Firstly the description must be published in an unrestricted and generally available book or journal (Watsonia Vol.21, 1986, pages 89-97).
  • The taxon must be given a name, which has never been previously used, and is in Latin (Hibernica is the Latin name for Ireland).
  • The species must be distinguished from all other members of the genus or species in which it is placed with a short Latin diagnosis.
  • A single herbarium specimen must be cited as the TYPE specimen. (9 specimens were collected, of which ours (DBN) is an ISOTYPE)

WHY LATIN ?

Botanical taxonomy is one of the few disciplines in which Latin is still used. It may seem archaic, but in fact it is extremely useful for the following reasons:
    1. Historical - Latin was the language of scholarship up to the 19th Century, and there is therefore a long history of plant descriptions.
    2. Latin is a dead language — it therefore never changes, and a 200 year old dictionary in Russian is therefore still ‘up to date’.
    3. International — The two examples (right) are new species descriptions from China and Russia — both can be easily understood through the common use of Latin.
    4. Precise and accurate — There are literally hundreds of terms for shape, texture, appearance and colour. see Botanical Latin (above)

VARIATION

Arabidopsis thaliana (L.) Heynh.
Thale cress is a widespread weed, which can grow from seed to maturity in just 30 days. It is also extremely variable, and is now used as the ‘Drosophila of the plant world’ in genetic studies. Variation of plants can be accurately recorded through herbarium specimens, and provide an essential reference for measuring and assessing variability of a species with season, soil type and locality. Writing accurate descriptions of plants for floras is dependent upon such material. The entire genome of this species is currently being mapped, in parallel with the Human Genome Project, and it will be the first species of plant for which the entire genetic code will be known. With the increasing ability to recover DNA from older and older herbarium specimens it may be possible, in the future, to study allele changes over historical time.

DISTRIBUTION

Gentiana verna L.
This plant is an alpine species, more common in the Alps. It is also found in great abundance in the Burren in County Clare. Herbarium specimens such as this one collected by Henry Levinge tells us that the plant was present near Ballyvaughan in 1892. Other herbarium specimens can give accurate information about a plants former or present distribution, helping to map the flora. … CENSUS CATALOGUES

EXTINCTION

Carex buxbaumii Wahlenb.
This species was only known from a small island, Harbour island, on Lough Neagh — it is now one of 8 species of plant known to have become extinct in Ireland. It remains a very rare plant in Scotland. There are over 50 species of vascular plant in Ireland that are endangered or vulnerable to extinction, with a further 80 species classified as rare to scarce. These species are described in the Irish Red Data Book.

ALIEN PLANTS

Senecio viscosus This groundsel is an alien plant that is becoming naturalised in Ireland. Up until the 1930’s it was only known as a rare plant in the two big east coast ports of Belfast and Dublin. Now it is spreading fast, and herbarium specimens enable us to chart this spread with specimens that can be checked for accurate identification at any time. As can be seen from the maps and habitat descriptions of the specimens, this species has a special fondness for railway line ballast, a habitat to which it is well adapted.

FLORAS

Herbarium collections provide an invaluable source of information on a plants variability, ecology, flowering dates and so forth, that can be used in Flora writing. Floras can cover any area from a county to a continent:
  • A City Centre –– P. Wyse Jackson and M. Sheehy Skeffington’s Flora of Inner Dublin
  • A County — P. Reilly’s Flora of County Cavan
  • Ireland — D.A.Webb’s An Irish Flora
  • British Isles — C. Stace’s New Flora of the British Isles
  • Europe — Flora Europaea

HOW TO COLLECT PLANTS

A plant specimen collected today can last many hundreds of years when stored in a herbarium. But a specimen without certain vital bits of data is valueless. These are:
1. WHO collected the specimen
2. WHERE it was collected – Geographical and Ecological.
3. WHEN it was collected.
4. WHAT it looked like when alive: Colour, size, smell etc.
Try to write all these details down and keep the data with the plant.

PRESSING

Take notes about features that will not be preserved on the dried specimen, such as colour, overall size, and smell. The first sheet (flimsy) surrounds the specimen, and then several sheets (drying papers) are placed between each specimen. Pad out bulky roots or branches with screwed up paper. Applying heavy weights, ensures that as the plant dries it remains flat. When arranging the plant try to make sure that the top and bottom side of leaves will show, and that as many features of the flowers and inflorescence are visible as possible.

DRYING

The best way is to dry the drying papers and not the plant. Put sheets of newspaper on top of radiators or other hot surfaces until they sound crackley, and then exchange these for the sheets in the press daily for the first 2-3 days. It is best to open the press after the first few hours to rearrange the now wilted plant so that you can make sure it is well laid out. Marine algae should be ‘floated’ onto a sheet of thick cartridge paper, and covered by a J-cloth, then pressed in the same way. Algae stick to the paper by their natural mucilage.

MOUNTING

Once dry, the specimens are glued or sewn to a sheet of thin card, to which the label, with collection data is also fixed. Mosses and Lichens and some Fungi are usually placed in a folded packet or envelope which is attached to the card.