November 23, 2012, by Brigitte Nerlich

Making plants science: The role of herbaria and images in botany

This is a one-off Guest Blog by Maura C. Flannery, Professor of Biology, St. John’s University, NY, reflecting on, what one may call, ‘making the private life of plants public’, or more precisely the use of herbaria, photography and art in botany, as well as issues of truth and trust. The blog is related to a visualisation project funded by the European Science Foundation, rather than to the Making Science Public Programme. However, there are some overlaps.

Pressing plants

In their research, botanists trust the plants themselves more than anything else.  By this I mean that the final arbiter of any discussion about a species’ characteristics is the type specimen, the plant which was used by the botanist who first described the species.  In most cases, the type is preserved as a dried and pressed specimen attached to a sheet of acid-free paper.  This “document” is kept in a herbarium, a collection of preserved plant specimens often associated with a natural history museum, botanical garden, or educational institution.  As Charles Darwin emphasized, there is variation within any species, so the type specimen can be quite different from other members of its species.  It is not a type in the sense of being typical or in the sense of archetype as Goethe used the term to signify the fundamental form from which the many varieties of plant parts arose.  Instead, the botanical use of the word type refers more to an anchor that holds the species description together, a reference against which other plants can be compared.

Since type specimens are so crucial to systematics—the science of naming, classifying, and determining the phylogeny of plants—it is not surprising that they are carefully preserved, often kept separately in a more secure location within a herbarium.  They are also the specimens that botanists are most likely to want to study when they are working on the classification of a particular genus or family of plants.  The need for both preservation and observation can lead to a problem.  Herbaria are managed very much as libraries, where specimens are borrowed from and loaned to other institutions, and while types are often requested to be loaned, herbarium curators are loathe to do so because of the chance, however slight, that mailing the specimen might lead to its loss or damage.

Access to specimens

There is also a social justice issue involved here because even though the greatest plant diversity, and therefore the source of the largest number of type specimens, is the tropics, most of the type specimens are in European herbaria in the countries which were formerly colonial powers (Figueiredo & Smith, 2011).  To visit these collections is often prohibitively expensive for biologists in Third-World nations, and even the expense of borrowing specimens can be a burden, if indeed these researchers know what to ask for because plant taxonomy is riddled with synonomies.  One way around these access problems is to image type specimens with high-resolution scanners.  This is being done through a number of national and international initiatives, perhaps the most significant of which is the Andrew Mellon Foundation’s multi-year project which began with imaging type specimens of African plants and ultimately expanded to include types from around the world.

One of the strengths of this project, called the Global Plants Initiative, is that it is scanning not only the specimens but a great deal of botanical literature as well.  From the very beginnings of modern botany in the 16th century, when botanical libraries, herbaria, and botanical gardens all were first founded, written descriptions were crucial to plant identification, along with the specimens themselves.  In fact, many botanists saw the textual descriptions as essential, while images were more to attract the interest of the less knowledgeable.  Others, however, have argued that modern botany could not develop until the invention of the printing press made consistent reproduction of accurate plant images possible.  While the text might survive transcription relatively well in copying manuscripts, images became less and less detailed and therefore almost useless for  identification.

In the first accurate illustrated printed herbals, the images were woodcuts that were sometimes colored, but that wasn’t essential for identification.  In fact, by the 18th century, as Michel Foucault notes, natural historians like Linnaeus had begun to develop a new way to describe species which relied on a limited set of qualities, namely, the form of the elements, their number, relationship  to each other, and relative size.  Color was not important, and could often be misleading as a diagnostic trait.  It is not coincidental that the two-dimensional herbarium sheet  and the 2-D illustration were sufficient to present necessary structural information.

Photography and art

With the development of photography, and its supposedly superior ability to present visual information objectively, it was assumed that botanical illustration would become obsolete, but this has hardly been the case.  Pen and ink drawings are the standard means of illustrating most of the botanical literature.  Photographs are not as good at providing clear depth cues as illustrations can be, and artists can eliminate or underplay extraneous characteristics while clearly portraying the essential ones.  Research has revealed that the camera and human vision work very differently, in that the latter makes sense of the world by emphasizing boundaries and the outlines of objects, while the camera treats each piece of information the same (Jonathan Kingdon, in Field Notes, 2011).  In other words, an illustrator does just what the visual system does in outlining structures and emphasizing boundaries.  It is no wonder that humans find such images satisfying and understandable:  a representation they can trust.

There is also another reason why art continues to be used in botany, especially in mycology, the study of fungi including mushrooms.  These organisms are often evanescent, drying up quickly and losing their characteristic form; the only way to capture all their important structural characteristics is to draw them in the field.  There are a significant number of cases where the type specimens for fungal species are watercolors; the dried organisms themselves have just lost too much information.  It is difficult if not impossible to press many fungi, so they are dried without pressing, resulting in some bizarre and not very useful lumps.  Photographs can be helpful here, but as different instruments provide different styles of seeing, so do photograph and illustration.  No one image, or even the specimen itself, gives all the information necessary for the researcher.  Some botanists, such as the orchid expert Oakes Ames, routinely attached drawings, watercolors, and photographs to herbarium sheets along with specimens (Flannery, 2012).  His trust was in a combination of images, but sometimes, in addition, he even attached excerpts from journal articles with text describing the species.  He obviously saw each modality providing some information, some truth, that was lacking in the others.

Image: Herbarium specimens at the Musée Nationale d’Histoire Naturelle, photographer: François Mey; Wikimedia Commons.

Note:  This commentary is based on the presentation I made at the European Science Foundation Conference on Images and Visualisation: Imaging Technology, Truth and Trust held in Norrköping, Sweden in September 2012.  Brigitte Nerlich chaired that conference, along with Andrew Balmer and Annamaria Carusi.

PS The Building for the Future Blog has a blog about this blog, with more pictures!

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