Written by Ranee Prakash, Senior Curator (Flowering Plants), Algae, Fungi and Plants Division, Department of Life Sciences, Natural History Museum, London.
A survey of flowering plant material stored in various fluid preservatives across several European herbaria/institutions was carried out a few years ago. The feedback received from the survey is shared and shows that the majority of the herbaria use 70% IMS (industrial methylated spirit) to store their collections.
The seed plant collections (stored in various liquids such as formalin, some have unknown liquids, and some mention poison) form a relatively small yet significant part of the botanical holdings at NHM (Natural History Museum). They include some important material dating back to the mid 1800’s and type collections such as the world’s largest flower Rafflesia arnoldii collected by Robert Brown. However, these wet collections have remained a somewhat underused asset and are in dire need of curatorial attention.
In continuation to this aim, a survey of flowering plants stored in spirit collections across various institutions in Europe was carried out in 2012 so as to assess what preservatives other institutions were using and what would be the best method to store the collections at NHM for posterity. The objective of this survey was to gather information on:
- How big the spirit collection is
- How the collection is used
- Which liquid preservatives the flowering plant collections are stored in
Nineteen institutions across Europe who hold flowering plants spirit collections were contacted using these basic questions and some information on the collections was retrieved from Index Herbariorum. A few institutions did not get back/ did not participate in this survey. The data gathered is shared in Table 1.
Name of Herbaria /Herbarium Code
|Information on Spirit collection||Type of Preservation method used/storage mixture used||
Total no. of Specimens (spirit)
|–||There have been no spirit collections made here at CGE for at least 25 years. Looked through the archives but can find no mention of which preservative was used in the past for the very few spirit collections they now have.||–|
|Conservatoire et Jardin botaniques de la Ville de Genève (G)
|Very limited spirit collection. It mainly consists of a few flowers personally brought back from the field in Madagascar||Local rhum (c. 60°)||–|
|Linnaean Society of London (LINN)||–||All dried material, mostly fish. No plant material n spirit.|
|Muséum National d’Histoire Naturelle
|–||Material fixed by FAA, alcohol or formalin, and preserved in the mixture: glycerol/ethanol/tapwater (equal volumes), except for 5% preserved in formalin 5% (especially historical collections)||c. 15,000 samples in c. 13,000 jars.|
|National Botanical Garden (BR)
|–||70% ethanol only||–|
|National Herbarium (L)
|The glycerol helps prevent the specimens from becoming brittle||The Leiden spirit collection [L]: Most specimens are stored in 70% ethanol with 5% glycerol added.
Utrecht collections [U]: Most specimens are stored in 70% ethanol with 5% glycerol added.
The Wageningen collections (WAG): not accessible on the website
|The Leiden spirit collection contains c. 35,000 specimens.
Utrecht collections: contains over 5,000 specimens.
|National Herbarium Nederland, Wageningen University branch
|–||70% ethanol + 1% glycerine;
When liquid gets low, the standard liquid is added again, so glycerine content may slowly rise (since it doesn’t evaporate where ethanol does).
|Royal Botanic Garden Edinburgh (E)
|The alcohol is a preservative and the glycerol prevents specimens becoming too brittle. (Formaldehyde solution is no longer used as a preservative due to associated health risks).
More accurate measurements are often possible from spirit-preserved material as the drying process may cause shrinkage; it also allows clear observation of the three-dimensional arrangement of flower parts. Rubber seals in the jar lids reduce evaporation, and the fluid level of all specimens is regularly checked.
|Specimens are stored in Copenhagen Solution: 70% industrial methylated spirit, 28% distilled water and 2% glycerol.
Diatoms are stored in 96% ethanol.
|over 7,000 specimens|
|Royal Botanic Gardens (K)
|The collection is rich in diversity, with 371 plant families represented. Much of the material consists of fleshy flowers and fruits that do not make good dried and pressed specimens.
In particular, the 3-dimensional arrangements of flower-parts are better observed in spirit specimens.
The collection is stored in a controlled temperature room, at 12-16°C, to reduce evaporation.
|All specimens are stored in ‘Kew Mix’, which contains 53% IMS (98/99% total alcohols), 37% water, 5% formaldehyde solution (38% w/w) and 5% glycerol; formaldehyde-fixative, alcohol-preservative and glycerol-prevent the specimens from becoming brittle.
Material is transferred temporarily into ‘Copenhagen Mix’ (70% IMS, 28% water and 2% glycerol) when it is removed from the collection for study.
|Over 70,000 plant specimens|
|The Natural History Museum (BM)
|Significant collections from across the world, some important type and historical material. Collections stored at 17 degrees and relative humidity 40-45%||Flowering plants stored in formalin; Kew mix, 70% ethanol, unknown liquids.||c. 2000 flowering plants|
|University of Oxford (OXF)
|–||About 80% of the collection is stored in Kew Mixture; the remaining 20% is stored in 70% ethanol (with 2% glycerol).
|Spirit collection (c. 4,000 bottles) is entirely vascular plants.|
|World Museum Liverpool (LIV)
Table 1. European Herbaria/Institutes holding flowering plant material in various liquid preservatives
Source: Index Herbariorum and feedback received/correspondence with all these institutions.
Note: These figures might have changed over these years and one must check with the respective curators for the latest figures.
The survey revealed that most of the herbaria/institutions across Europe have important holdings of plant material and the majority of them use 70% IMS. Some institutions also add glycerol ranging from 1 to 5% to 70% IMS. Kew Gardens (K) uses Kew Mix and Copenhagen Mix whereas Royal Botanic Garden Edinburgh (E) uses Copenhagen mix. Oxford (OXF) had 80% of their collections in Kew mix, the rest in 70% ethanol with 2% glycerol.
Since the flowering collections at NHM will be recurated in the near future, feedback from this survey, along with advice sought from other curators at NHM, best curatorial practices from various sources such as care and collections of natural history collections (Bedford, 1999; Moore, 1994, 1999 & Notton, 2011) and skills learnt from the course on “Fluid Preservation” by Simon Moore will be taken into consideration to recurate the collections. Since the survey was conducted, “The Decision Making Model for the Conservation and Restoration of Fluid Preserved Specimens” by Andries J. van Dam (2004) and Rob Waller’s risk assessment (2013) have already been applied to the collections and based on the recently conducted JTD (Join the Dots) survey in 2018 at the Natural History Museum, we have scored the collections as high priority for a recuration project. This was a very small survey and some regional and other institutes across Europe have been missed out.
I am grateful to all the curators and colleagues across various institutes who participated in this survey. I am also thankful to Miranda Lowe (Principal Curator, Crustacea), Oliver Crimmen (Senior Curator, Fish), Jan Beccaloni (Curator, Arachnida & Myriapoda) and Specialist Andries J. van Dam for the useful advice. I am grateful to Jovita Yesilyurt (Senior Curator-in Charge, General Herbarium III & IV) and Dr Mark Carine (Principal Curator- in charge, Algae, Fungi and Plants Division) for the encouragement and to David Notton (Senior Curator- Hymenoptera) for reviewing the paper and the useful comments.
Andries J. van Dam. 2004. Decision Making Model for the Conservation and Restoration of Fluid Preserved Specimens. Leiden Museum of Anatomy, Netherlands. (online, accessed 11 April, 2019).
Bedford, D. J. 1999. Vascular plants. In: Carter, D. & Walker, A. (eds). (1999). Chapter 3: Care and Conservation of Natural History Collections. Oxford: Butterwoth Heinemann, pp. 61 – 80.
Moore, S. J. 1994. What Fluid is This? Biology Curators Group Newsletter, Vol 6, No 4, pp. 44 ‐ 45.
Moore, S. 1999. Fluid Preservation. In: Carter, D. & walker, A. (eds). 1999. Chapter 5: Care and Conservation of Natural History Collections. Oxford: Butterwoth Heinemann, pp. 99-132.
Notton, D. 2011. A New practical Method for Profiling and Topping Up Alcohol Preserved Entomology Collections. NatSCA News, Issue 21, 44 ‐ 49.
Waller, Rob. 2013. Excerpt from Robert Waller. Assessing and Managing Risks to Your Collections. (online, accessed: 10 April 2019).