Field of Science

Who invented the dichotomous key?

It's easy to take dichotomous keys for granted, and they are a wonderful tool for sorting through and calling your attention to significant details. After working your way through a complicated and detailed dichotomous key, and arriving successfully at an identification you get quite a feeling of achievement. One such key, Gleason and Cronquist's Manual of Vascular Plants of NE United States and adjacent Canada (NY Botanical Garden) puts a tremendous amount of taxonomic identification power in your hands (It is a bit hefty, so use 2), once you learn how to use it and get a bit of experience from a seasoned pro. In case you are unfamiliar with such devices, dichotomous keys offer you pared choices with each choice leading you to another pair of choices, and so on until an identification is reached. But who invented the idea? As best the Phactor can recall, someone said Jean Baptiste Lamarck, he of inheritance of acquired characters fame, had introduced the dichotomous key in Flora Francaise (1778), but seldom does that get mentioned as one of his scientific accomplishments. And now one of my colleagues (Lawrence Griffing) says that a botanist, Robert Waller, gave a talk to the Royal Society of London some 100 years earlier entitled: Tables of the English Herbs reduced to such an order, as to find the name of them by their external figures and shapes (27 March 1689). (The entire article may be behind a fire wall as it was just published, but us insiders can get the pdf file if anyone is truly interested.) This does not mean Lamarck got the idea from Waller, just that such a tabular approach was introduced earlier. Waller was very modern by linking his key to water color illustrations of the British flora and supposedly these illustrations are accessible online at the British Library (thus the origin of a previous post), but even after registering, the Phactor was unable to find the illustrations, or even get back in again, and not enough time to really fight with it. If anyone else is successful, do let us know.


BrianO said...

Dear Phactor,

Waller´s illutrations are available directly on the Royal Society website at:


bom ano !


The Phytophactor said...

Thanks BrianO! Wonder why I couldn't get there?
Here's the link to Waller's illustrations.