In addition to the world-famous gardens, Kew is home to several preeminent research collections and facilities, once of which is the herbarium. Now containing over seven million botanical specimens, it is one of the largest such collections in the world. It is a very busy research institution, but they have just started organising extended visits and tours, and I managed to get on the first one.
There have been gardens at Kew since the eighteenth century, which evolved over the years until their management was taken over by the state in 1851. William Hooker had become director in 1841, and he made his personal herbarium collection available for research at Kew. Other collections were then added from the 1850s onwards, especially many important tropical and colonial plant collections. To begin with, these were all stored in Hunter House on the edge of the gardens, but by the 1870s the collection was already so large that the first purpose-built wing of the herbarium was required.
Since a herbarium contains such a large amount of combustible material, gas lights were not advisable, so the older wings of the building have large windows to enable as much light as possible to enter the interior. Even so, in grey winter months it would have been decidedly gloomy in there and it may well have been hard to study the fine detail of the specimens.
There are now five wings and a basement, and the collection has recently completed its five-year reorganisation so that, for the first time in its history, the specimens are arranged taxonomically.
Even so, not all the materials in the collection can be stored on nice flat sheets. Many plants produce large seeds and other structures, and these are stored in other drawers and boxes.
Among the collection are 330,000 type specimens, the original specimens from which the first description of a species was made. Specially identified in red folders, these jump out at you when you open one of the cupboards, and are clearly the most important part of the herbarium holdings. These type specimens may also include duplicate types from other herbaria (isotypes). Along with the types from many of the other major herbaria in the world, these have now all been digitised and the catalogue is available on the Kew website.
The first type specimen we saw during the day was the bindweed Merremia kentrocaulos, and which starts to illustrate the richness and complexity of the materials. The high resolution image shows the extent of the labelling on these sheets. This turns out to be an isotype of a plant first collected by the Bavarian botanist Georg Wilhelm Schimper by the river Takkaze in Ethiopia in 1838. Initially named Convolvulus kentrocaulos by Ernst Gottlieb von Steudel, and added to the Kew collection in 1868, subsequent work on the classification placed it in the genus Merremia, which determination was confirmed in 1992.
Moving on, we had a look at a plant from Britain, in this case Peppermint (Mentha x piperata), a cross between watermint and spearmint, which included collections from many dates and sites.
I didn’t realise quite how large the family of gingers is. The type specimen of Zingiber clarkei was collected by the British botanist Charles Baron Clarke on 18 August 1870 from Rishap in Darjeeling. This shows that the specimen sheets may also contain sketches and even more elaborate illustrations as well. Clarke was a prominent Victorian botanist, who did a large amount of work on sedges, and was also elected President of the Linnean Society in the 1890s. His herbarium comprised over 25,000 specimens, most of which is now at the Natural History Museum and Kew, but some specimens are distributed throughout the world.
Finally, among all the specimens we saw during the day, that of the Ross Lily (Bulbinella rossii) was perhaps the most interesting historically, since this was also a type, and was on the distinctive blue paper which indicated that it was collected by Joseph Hooker, Darwin’s long-term friend and supporter. He took over as the director of the Gardens from his father in 1865, which was several years after his expedition to the Southern Ocean, Antarctica and New Zealand. This plant was one of the subantarctic megaherbs collected from Campbell Island in 1840 (the date on the herbarium sheet is given as 1845, though that is certainly wrong since the expedition ran from 1839-43), where it is endemic. As can be seen from the sheet, Hooker first named it Chrysobactron rossii, though it was subsequently moved to another genus.
So, not only does a great herbarium give us the opportunity to study the plants themselves, but they also open up an amazing perspective on the history of global botany, plant collecting, and the complicated networks of specialists over the past two hundred years and more. Visiting Kew has made me want to research some of the great Victorian botanists based in Sussex, such as William Borrer, with a view to trying to reconstruct their favourite sites and collecting locations.
Many thanks to Nina Davies and Aurélie Grall for a great day.
 “Georg Wilhelm Schimper.” Wikipedia. Wikimedia Foundation, n.d. Web. 31 Jan. 2016. <https://en.wikipedia.org/wiki/Georg_Wilhelm_Schimper>. See also the online edition of his work on Ethiopia: Schimper, Georg Wilhelm. “In Abyssinia. Observations on Tigre.” Ed. Andreas Gestrich and Dorothea McEwan. German Historical Institute London, 2015. Web. <http://www.ghil.ac.uk/Schimper>.
 “Charles Baron Clarke Papers, 1832-1906.” American Philosophical Society. N.p., n.d. Web. 02 Feb. 2016. <http://www.amphilsoc.org/collections/view?docId=ead%2FMss.B.C555-ead.xml>.
 “Clarke, Charles Baron.” Index of Botanists. Harvard University Herbaria & Libraries, n.d. Web. 2 Feb. 2016. <http://kiki.huh.harvard.edu/databases/botanist_search.php?botanistid=350>.
 “Joseph Dalton Hooker.” Wikipedia. Wikimedia Foundation, n.d. Web. 02 Feb. 2016. <https://en.wikipedia.org/wiki/Joseph_Dalton_Hooker>.