Are Pressed Plants Windows Into World History?

Before its residence at the Smithsonian's National Museum of Natural History, this pressed plant (Cyananthus macrocalyx subspecies spathulifolius) was housed at London's Natural History Museum where it survived a bombing during World War II (Photo Credit: Ingrid P. Lin, Smithsonian).
Before its residence at the Smithsonian's National Museum of Natural History, this pressed plant (Cyananthus macrocalyx subspecies spathulifolius) was housed at London's Natural History Museum where it survived a bombing during World War II (Photo Credit: Ingrid P. Lin, Smithsonian).

The botanical specimens housed in the U.S. National Herbarium (USNH) at the National Museum of Natural History have been assembled over the course of several centuries and the collection continues to grow today. Currently, the herbarium contains over 5 million plant specimens and serves as an encyclopedia of the Earth’s flora. These specimens are irreplaceable sources of information regarding the diversity of species and the habitats they come from. They play a critical role in taxonomy, systematics, anatomy, morphology, ethnobiology, paleobiology, and conservation biology. The specimens can be used to discover and confirm the identity of a species new to science. They provide locality data for conservation assessments. They can document the effects of climate change on flowering phenology. They also provide material for DNA analysis and conservation genetics.

For world history buffs, these specimens provide a peek into the past, not only into the expeditions in which the plant was collected, but every so often they document major social events. The clues are usually found on annotation labels attached to the herbarium sheet. Most often these annotation labels tell us of the changing understanding of which species you’re holding. But every now and then you get a glimpse into history.

Take for instance USNH specimen 2318036 pictured above. The preserved plant attached to the sheet is a species in the bellflower family (Campanulaceae) named Cyananthus spathulifolius (which has now been renamed Cyananthus macrocalyx subspecies spathulifolius). The collection label, which details the collection event, tells us that it was collected on July 27, 1936, from the rocky hillslopes of Tibet at 14,000 feet by the English/Scottish team of explorers, Frank Ludlow and George Sherriff. The sheet has a stamp telling us that it currently resides in the U.S. National Herbarium. The collection label indicates that it was previously held in the herbarium of the British Museum (“Ex Herbario Musei Britannici”).

The annotation label on this sheet makes this specimen unique. Annotation labels are attached to specimens at a later date with new or additional information about the specimen. The label on this specimen reads “Sheet damaged by enemy action at British Museum (Natural History) on 10 September 1940.” During World War II, German forces targeted London, and London’s Natural History Museum was badly damaged when 28 bombs landed on or near the museum during the month of September 1940. British scientists did their best to prepare for war by protecting the museum’s specimens. Earlier, after war was declared, collections from a number of research departments such as geology and entomology were removed from the museum and sent to private homes in the countryside. Sadly, many botanical specimens and books that hadn’t been moved yet were either harmed or destroyed when two bombs went through the roof of the botany department.

The bellflower specimen collected by Ludlow & Sherriff was damaged but survived. In 1954, the specimen was sent to the U.S. National Herbarium as part of an exchange of specimens with the Natural History Museum of London. Museums and herbaria around the world are steeped in a history of sharing and collaboration, and they have a long history of collection exchange. By moving specimens around the world, exchanges allow herbaria to expand the geographic and taxonomic ranges of their collections. Duplicate specimens, those collected from the same plant or population by the same collector at the same time, are often used in exchanges. By sending duplicates to a number of herbaria, the specimen and the valuable data associated with it are insured against loss or damage that may occur at one particular location.

The Natural History Museum of London wasn’t the only institution to suffer greatly during World War II. The herbarium of the Botanical Museum Berlin-Dahlem in Germany, which at the time housed 4 million specimens, was destroyed in a bombing raid in March 1943. While approximately 500,000 specimens were saved (the collections of German botanist Carl Willdenow were safe-guarded in a bank vault), the majority perished. A similar fate befell the herbarium of the Philippine National Museum in Manila, which was burned down a day before the liberation of Manila in 1946. Fortunately, before the war began, duplicates of historic Philippine plant specimens had been sent on exchange to the U.S. National Herbarium and other American herbaria.

More recent examples of museum damage and the loss of specimens and artifacts include the destruction and looting of museums in the Middle East after the political uprisings of 2010 and the destruction of Gabon’s National Herbarium by arsonists during post-election riots in 2016. Natural disasters have destroyed natural history collections as well, such as the devastating San Francisco earthquake on the California Academy of Sciences in 1906 and Hurricane Katrina’s flooding of the herbarium of the Gulf Coast Research Laboratory in Ocean Springs, Mississippi in 2005.

Man-made and natural disasters aren’t the only way specimens might meet an unfortunate fate. While the exchange and loan of botanical specimens may be considered a safe-guard, sending material through the mail carries an inherent risk. During transport, fragile specimens may get lost or suffer damage. A worst case scenario took place recently when type specimens dating back to the mid-1800s were destroyed while in transit from the French National Museum of Natural History in Paris to Queensland's herbarium in Brisbane, Australia.

As a conservation biologist, I value specimens for the data written on the labels. I use the data to assess the conservation status of the world’s flora. Irreplaceable plant specimens may represent the last bit of evidence that a species now extinct had existed on Earth. For example, my colleagues and I recently completed a conservation assessment of 263 endemic plant species from the Lesser Antilles. Two montane species that we assessed, a false pimpernel (Lindernia brucei) and a brushholly (Xylosma serrata) are both known only from single volcanic sites on the islands of St Vincent and Montserrat, respectively. Neither species has been recollected since the most recent volcanic eruptions of 1979 and 1995 on these islands. With the only known populations of these two species destroyed by volcanic flow, both the false pimpernel and the brushholly may now be extinct. What little we know about these plants is preserved on a few herbarium sheets.

The U.S. National Herbarium is preserving its rich specimen data by digitizing its entire collections. Working its way through 5 million specimens, the digitizing team has recently imaged and databased its one millionth specimen. Digitization benefits museum scientists by creating a detailed inventory of plants and records at each herbarium. Researchers can access specimens from all over the world right from their desks without the underlying risk of mailing specimens.

While digitized records of specimens are a great way to preserve data, the specimens themselves are still necessary to researchers. Only the specimen, and not a digitized photograph, provides material for DNA analysis, pollen for taxonomic and pollination studies, and leaves for chemical analysis. Moreover, online data may not be permanent, as online servers are vulnerable to computer viruses or hacking and data could be intentionally or accidentally removed or deleted. Digitizing the records of our herbarium specimens is important for expanding our scientific reach, but safely securing museum specimens is essential for current and future botanical research.