I suspect that most visitors to museums give little thought to the hidden world behind the main exhibition areas. I certainly didn’t, and before I saw this workshop advertised with BSBI I wasn’t even aware there was a herbarium in the museum building!
A herbarium is a collection of plants used for scientific study and this particular one includes vascular plants (including flowering plants) and cryptogams (including seaweeds, mosses, lichens etc.). The Welsh vascular herbarium is basically a large room containing steel cabinets that are filled with dried plant specimens collected over a period of time. Those that are in the main part of the collection are called voucher specimens and are of each species. They are organised in folders by vice county with the Welsh samples on top and those of other countries below. (Type specimens are stored separately and indicated with a red mark on the folder). All the plants are catalogued and the folders may contain numerous voucher sheets which is useful in comparing natural variation and characters.
During the day we were given the opportunity to mount some grass specimens and this highlighted the painstaking patience and dedication required to maintain such a large collection. Of course this is only part of the story and each plant has to be first correctly dried and then pressed to keep as many of the original characteristics of the plant as possible. It has to be accurately labelled with information about the species, location, date and collector and then be kept free of all the natural agents that would either eat or decay these plants. Amazingly the whole collection is rotationally frozen to kill off any unwanted organisms.
Conservation of the material is an important part of the work. Older material is gradually being re mounted onto acid free cotton paper with cotton straps that are applied with archive quality reversible EVA glue. Vicky Purewal explained how she has developed techniques to identify some of the more harmful products that were used in the past to preserve specimens. These may have included pesticides containing arsenic and mercury which although present in very small amounts on each plant could reach harmful levels of exposure for those curators handling them on a daily basis.
After the vascular plants we were shown around the cryptogam collection. The museum houses the BBS (Bryological Society of the British Isles) collection of bryophytes. These are contained in smaller wooden drawers than the vascular plants with individual specimens either stored in paper bags or cardboard boxes and polythene bags.
As well as the actual plants there is an extensive library of botanical books and periodicals, many of which I would now imagine are difficult to find. Very kindly the staff brought out some of their Nature Prints which I described in an earlier blog post. These are incredibly detailed and beautiful illustrations taken as prints from the plants themselves and it was a privilege to see them.
I took the opportunity at the end of the day to check out my tooth edged leaf lobes of Ceratocapnos claviculata with some of the voucher specimens in the collection. A couple of leaf lobes did have a few teeth but nothing as definite as mine. I also examined the specimens of Anemone nemorosa, and yes they all seemed very hairy!
So to conclude the Welsh National Herbarium is an amazing resource and I would like to thank everyone who showed us around. As Sally Whyman explained it is there to be used and I would encourage everyone to do just that. I am aware there is a lot more that the museum has to offer that I have not touched on. For more information visit https://www.museumwales.ac.uk/biosyb/vascular/collections/