Almost 100 years before the publication of the first text-based dichotomous key, an image-based dichotomous key was presented to the scholars of the Royal Society in London. The year was 1689.
The story behind this identification tool, its creator and the scientific community’s reaction to it, is the focus of Who Invented the Dichotomous Key? Richard Waller’s Watercolors of the Herbs of Britain by Lawrence R. Griffing.
Griffing provides fascinating insight into the history of the dichotomous key.
What is a dichotomous key, exactly?
It’s an identification tool. Think of it as a field guide’s more analytical cousin. You can’t flip though a key as casually as you can flip through an illustrated pocket field guide. Keys require users to sit down and observe a specimen carefully. The identification process requires the user to make a series of observations in a very methodical way and to choose between the presence or absence of a specific feature or to make “either/or observations” (Griffing, 2011) resulting in a user choosing one feature (or condition) over the other. This methodical dichotomous decision-making process leads a user through a key and eventually to a species description matching the specimen collected or observed by the key’s user.
Richard Waller’s idea for an image-based dichotomous key came from a suggestion he made to naturalist, John Ray, author of Historia Plantarum (1686). Waller suggested that Ray use images in his dichotomous tables to make plant identification easier for beginners (Griffing, 2011). Ray did not appreciate Waller’s suggestion, nor the implication that his descriptive text was not good enough (Griffing, 2011). Unaffected by Ray’s negative defensive reaction, Waller continued to build upon his idea for an image-based dichotomous key so that “one wholly ignorant in Plants may know how to find any unknown Plant” (Waller (1688), as cited in Griffing 2011).
Griffing (2011) goes into great detail about how Waller’s image key may have been constructed, using Waller’s own description of his key. Griffing (2011) includes in his paper, figures of tables Waller could have created using images from the archives of The Royal Society. How Waller actually assembled his images is not known.
Interestingly, Waller’s visual key did not receive broad support from his colleagues at The Royal Society. Griffing (2011) explains the lukewarm response Waller received could have been attributed to the fact that Waller was ahead of his time and that Waller was creating a tool to be used by beginners and herbalists, an audience quite different from the Society’s expert audience.
The botanical watercolor paintings of British grasses and wildflowers Waller used in his key can be viewed online as a Turning-the-Pages document on the website of The Royal Society. Waller’s plant studies feature paintings of whole plants accompanied by close-up studies of a plant’s unique characteristics. Waller completed his close-up studies in pencil. Look for them as you view Waller’s work. In his paper, Griffing (2011) makes reference to select paintings in the Turning-the-Pages document. You may want to view Waller’s paintings while reading Griffing’s article. Be advised that the page numbering is off between MS/131 and the online version (Griffing, 2011).
Griffing, Lawrence R. 2011. Who invented the dichotomous key? Richard Waller’s watercolors of the herbs of Britain. American Journal of Botany.