Why do we label the specimens?
A specimen collected by Darwin, incorporated into the Kew collection in 1867. It has Darwin's original notes and subsequent annotations by other botanists working with this specimen. Note the relative paucity of information recorded on labels at that time.
A modern collection made in November 1992 in Madagascar by David Dupuy, Gwilym Lewis and Brian Schrire from Kew. A wide range of information is recorded on the label. The small slip pasted above the label indicates the determination (identification) of the specimen and that this is a type specimen for the name Millettia nathaliae Dupuy and Labat - this species having been first published by these two authors. Additional individual fruits and flowers are stored in a transparent envelope at the top left hand corner of the herbarium sheet. These are available for more detailed analysis with microscope or in the laboratory without destroying the main specimen.
A Cucurbitaceae specimen collected in Brazil by Richard Spruce in 1849. Compared to collectors working today he recorded limited information on the label. Notice that he wrote in Latin so as to facilitate communication with botanists all over the world.
An image of a page from a Spruce notebook where far more information was recorded than was included on the field label.
There are two reasons for having a label on each and every specimen in the collection.
- To distinguish between one collection and another – just as in a museum every object is identified by a unique number or barcode so curators of a herbarium collection and scientists communicating with one another around the globe need some unambiguous way of referring to each individual specimen.
- To record additional important information about the plant as it was when collected. This is especially important for trees — where the herbarium specimen is only a small portion of the plant.
How do we uniquely label specimens?
Many specimens of the same plant species might have been collected in different places, at different times and by different people and so we need some other way of referring unambiguously to the individual specimen. Each specimen is labelled using two pieces of information: the name of the person(s) that collected the plant and that person's collection number.
At the start of their career, each botanist collects their first collection - this is known as number 1. They then move on to make collection number 2 and so forth. Active collectors will collect many thousands of plants during their lifetime, thus specimen R.Harley 50594 is the 50594 th specimen collected by Ray Harley. This number is unique: Harley will have no other collection sharing this number. "R.Harley 50594" is a particular collection of Agrianthus guiliettiae which he made on the 31 December, 1991 in Bahia, Brazil. At the time Harley will have made duplicate collections and sent copies to various herbaria in Brazil and around the world. Every one of these duplicates, in whichever institution it is found, will be referred to, and recognised as, "R.Harley 50594". This simple procedure allows scientists to publish scientific papers and books referring to the specimens they have seen and to know that they are communicating effectively with one another about the plants studied.
As electronic databases and management of large collections become more sophisticated, herbaria such as Kew, have started to bar-code their collections or provide some other unique electronic tag for each specimen. Some flowers taken by Harley in 1991 as part of the collection "R.Harley 50594" and today preserved in Kew's spirit collection have been assigned the code 58976.000, uniquely defining this object in our collection and differentiating it from copies of "R.Harley 50594" stored in the herbaria of the New York Botanical Garden and the University of São Paulo.
What other information is recorded on the label?
A plant in the reference collection is most useful when we know exactly where it was collected (in modern collections this is recorded using GPS equipment) and a description of its habitat (ecology), appearance when alive (especially important since flower colour for example will be lost when the plant is dried) and other information such as the uses to which it may be put locally or insects that were seen visiting the flowers.
Careful labelling of plant samples is important and modern plant collectors record a wealth of useful information on the specimen label. A label typically includes the plant family, a first attempt to identify it, any popular (common) names used locally, plus its position and locality and the date of collection. The latter gives biologists studying reproductive behaviour vital clues to the times of the year a plant can be expected to be in flower and fruit. Features of the plant that cannot be collected (the height of a tree, the presence of latex) or that get lost upon pressing (colours and odours) are also annotated, as they can help identify the specimen later on.