Oklahoma Native Record 77 Volume 10, December 2010

“BEING A METHOD PROPOSED FOR THE READY FINDING…TO WHAT SORT ANY PLANT BELONGETH”

Ronald J. Tyrl Emeritus Professor of Department of Botany Oklahoma State University

As any ONPS member will attest, it species name. Sometimes my first try is doesn‟t take many field trips into the prairies successful, but more often I have to make and forests of Oklahoma to encounter an several or even numerous attempts. However, unknown plant and have to ask, “What is it?” nothing is more satisfying than to be able to The easiest way to identify it is disarmingly say “Gotcha! I know who you are!” In the simple; ask someone who knows! This following essay, I offer an overview of the approach works well when an expert is near at origins and evolution of taxonomic keys, hand, ready to name . A second aspects of their nature, and suggestions on approach is to compare the unknown plant how to use them successfully. with photographs or illustrations in field guides specific for Oklahoma. Unfortunately, Origins and Evolution of the Key— the major drawbacks in using such guides are Taxonomic keys have been the mainstays of that they typically illustrate only showy- plant identification for more than 250 years. flowered species and may not include all Their origins, however, are considerably older species present in the area. The ideal way to and can be traced to the classifications of identify an unknown plant is to use a Aristotle and Theophrastus, based on taxonomic key – an artificial analytical device fundamentum divisionis or the “principle of for identification which offers a progressive division” and those of 17th Century series of choices between pairs of alternative naturalists (Voss 1952; Stuessy 1990). Edward features (Lawrence 1951). Taxonomists have G. Voss, a plant taxonomist and former been writing and using them for centuries as Curator of the Herbarium at the University of they have inventoried the world's flora (Voss Michigan, published an excellent, 1952). Go anywhere in the world and if a comprehensive history of taxonomic keys in taxonomic key is available, unknown plants 1952. It was a delight to have discovered this can be identified. paper many years ago, and I have excerpted Even after more than 45 years of working aspects of it in the following very abbreviated as a plant taxonomist, I still take pleasure in summary. Voss describes how taxonomists the challenge of identifying a totally unknown such as Robert Morison, , Augustus plant, i.e., one that I have no inkling of what it Rivinus, and the anatomist Nehemiah Grew is. It is a delight to sit down at a dissecting presented their classifications (1672, 1686, microscope with dissecting needles in hand, to 1699, and 1682, respectively) in a tabular examine the plant‟s many features, to revel in outline form and used brackets to relate and its beauty and complexity, and to work my contrast their groups (essentially diagrams of way through the key to arrive, eventually, at a relationships; Figure).

Tyrl, R. J. https://doi.org/10.22488/okstate.17.100078 78 Oklahoma Native Plant Record Volume 10, December 2010

Flowers perfect; styles and stamens both present

Flowers solitary

Petals fused

Petals alike; as in Campanula and Convolvulus Flowers Petals different; as in Aristolochia and Viola

Petals free; as in Brassica and Alsine

Flowers in heads; as in Calendula

Flowers imperfect; styles or stamens lacking

Figure A portion of the classification of John Ray appearing on page 20 of Volume 1 of his Historia Plantarum (1686), showing his groups and the brackets used to relate them. Latin text of Ray‟s groups translated and abbreviated.

I must stress that these bracketed tables published in 1778. Francis Arthur Bather were not keys and their purpose was not (1927; cited in Voss 1952), in an address to identification, but rather classification. As the Geological Society of , described Voss notes, Grew, however, did articulate the the significance of Lamarck‟s keys in biology idea of using a dichotomous key to identify by stating: plants. An appendix to the second part of A key is not a classification, but a book four of his Anatomy of Plants (1682) is method of analysis. The idea was first titled “Being a Method proposed, for the explicitly brought forward by Lamarck at the ready finding, by the Leaf and Flower, to what very beginning of his career. Having asserted Sort any Plant belongeth.” In it, he describes that every species of French plant could be how one might go about identifying an more readily determined by a purely arbitrary unknown plant and lists characteristics of the analytic key than by the Linnean system with leaves and flowers that should be used in its its mixture of supposed reality and ordered identification. It was suggested that his title arbitrariness he was challenged to produce would be a catchy opening for this essay, and such a key, and this he did within twelve thus I have unabashedly used it. months… Although Carolus Linnaeus, typically Since the time of Lamarck, keys have been known as the father of , apparently an essential part of biological endeavor and used clavis, the Latin word meaning “key,” to used for the identification of all living describe these bracketed diagrams in his 1736 systems. They are now an integral part of the edition of Bibliotheca Botanica, the famous literature of taxonomy, ecology, and indeed French naturalist and early proponent of the any discipline dependent upon plant theory of evolution, Jean Baptiste de Lamarck, identification, e.g., range management, wildlife is generally credited with the development and biology, and conservation. Keys for the first publication of the strictly dichotomous identification of plant families, genera, and keys specifically for identification purposes. species typically are incorporated in floristic He used them throughout his Flore Francoise treatments known as floras or manuals. These

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works are designed to facilitate identification of the applicable alternative character state of the plants in an area and generally comprise leads you to other pairs of alternative the keys, descriptions of the morphology of character states, e.g., petals yellow OR petals white each taxonomic group, and abbreviated or leaves simple OR leaves compound, and comments about each group‟s distribution, ultimately to the unknown plant‟s scientific ecology, flowering time, and taxonomic name. Using a key is thus analogous to relationships. Please remember that the word following a forking path with each fork “flora” also is used as a collective noun for all forming a “Y”. To reach the proper of the plants in an area, i.e., the botanical destination, i.e., identification of the unknown equivalent of fauna. plant, you must take the correct path (choose the applicable character state) at each fork. Nature of a Key—But what is a key? It is I liken a key to a Victorian maze with its simply a device that presents its user (you) numerous forking paths among screens of with a progressive series of choices between boxwood or hazel. Correct choices made at pairs of alternative, generally mutually each fork lead one to the center or exit. exclusive features. For example, you might be For example, a key to five Oklahoma species asked to examine your unknown plant and to might read as follows: decide whether it is a tree OR an herb. Selection

1. Plants trees. 2. Leaves opposite; venation palmate. Fruits double samaras...... Acer rubrum (red maple) 2. Leaves alternate; venation pinnate. Fruits nuts partially enclosed in involucral caps (acorn)...... Quercus stellata (post oak) 1. Plants herbs. 3. . Leaves alternate. Corollas rotate. Ovaries inferior...... nuttallii (prairie parsley) 3. Inflorescences panicles or racemes or spikes. Leaves opposite. Corollas bilabiate. Ovaries superior. 4. Stems square. Inflorescences spikes. Fruits nutlets...... Prunella vulgaris (heal-all) 4. Stems terete. Inflorescences panicles or racemes. Fruits capsules...... Penstemon oklahomensis (Oklahoma beardstongue)

The pair of alternative features at each features, and making choices until a scientific fork is termed a couplet, and the alternatives name is reached. of a single couplet are called leads or legs. To Thus, using the key above, if you observe facilitate use of the key, the couplets typically that your unknown plant is an herb with are successively indented to the right, with terete stems, opposite leaves, panicles, both leads of a single couplet equally indented bilabiate corollas, superior ovaries, and and generally numbered. After observing the capsules, you identify it as _?_ (see the last unknown plant‟s features, you commence paragraph of this essay to check your keying at couplet 1 by reading both leads and identification). I have to admit that a glossary making a decision as to which lead applies. of taxonomic terms is indeed handy to have After one of the two leads has been selected, available when you first begin keying. you proceed to the first indented couplet Technical descriptive terms–the bane of immediately under it. The couplets under the beginners–are essential to ensure accuracy and non-selected lead are disregarded because the brevity. However, the more you use a key, the features listed aren‟t those of your unknown more familiar the terms will become, and your plant. You continue reading the leads of reliance on the glossary will quickly decline. successive couplets, observing the plant‟s

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Types of Keys—The key presented above is couplet are always together. Use of a an indented key, so named because each bracketed key is the same as for an indented successive couplet is indented to the right. In key and involves observing the plant‟s contrast, a bracketed key has couplets that are features, reading both leads, and making a not indented but rather you are directed to the choice. A bracketed key to the same five appropriate succeeding couplet via a number species appears below. at the right-hand margin. The leads of each

1. Plants trees...... 2 1. Plants herbs...... 3 2. Leaves opposite; venation palmate. Fruits double samaras...... Acer rubrum (red maple) 2. Leaves alternate; venation pinnate. Fruits nuts partially enclosed in involucral caps (acorn)...... Quercus stellata (post oak) 3. Inflorescences umbels. Leaves alternate. Corollas rotate. Ovaries inferior...... Polytaenia nuttallii (prairie parsley) 3. Inflorescences panicles or racemes or spikes. Leaves opposite. Corollas bilabiate. Ovaries superior...... 4 4. Stems square. Inflorescences spikes. Fruits nutlets...... Prunella vulgaris (heal-all) 4. Stems terete. Inflorescences panicles or racemes. Fruits capsules...... Penstemon oklahomensis (Oklahoma beardstongue)

Thus if you observe that your unknown Superbowl, and we label movies good or bad. plant is an herb with alternate leaves, umbels, We therefore feel comfortable using rotate corollas, and inferior ovaries, you will dichotomous keys. However, taxonomic keys identify it as _?_ (see the last paragraph of this written in the 1800s and early 1900s were not essay to check your identification). always strictly dichotomous. Some authors As is obvious, the bracketed key saves occasionally included trichotomous, considerable space because the couplets are tetrachotomous, and even pentachotomous not indented to the right with the lines of text couplets. As you might expect, the third, getting shorter. However, using it is time- fourth, and fifth alternatives might easily be consuming. Every couplet must be read in overlooked thus leading to errors in order, it is harder to locate succeeding identification of the unknown plant. couplets, and it is harder to retrace one‟s Fortunately, the dichotomous key has become previous decisions. In an indented key, you the standard. quickly skip the couplets that are not Indented and bracketed keys are also applicable and have a better overview of what known as single-entry or single-access keys in decisions you have made previously. As you that they have a single starting point – the become familiar with more plants and see character or characters of couplet 1. There is their names in the couplets, you develop a just one route or sequence of characters sense of whether you are on the “right” path leading to the identification of an unknown in identifying your unknown plant. plant. If one or more characters appearing in Branching by repeatedly forking into pairs the couplets of the key are not available to the of mutually exclusive leads (choices), indented user, identification of an unknown plant and bracketed keys are termed dichotomous becomes more difficult and sometimes keys (from the Greek dicho meaning “in two” impossible. An alternative to the dichotomous or “split”). Choosing between only two key is the multiple-entry or multiple-access character states is perhaps an innate part of key. Also known as a polyclave or polyclave the human intellect. We tend to like true and key, the multiple-entry key, as its name false questions, we cheer the teams of the suggests, allows the user to select the

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characters used to identify an unknown plant states. The names of species not possessing from a character set that describes the plants the features of the unknown plant at hand of an area or taxonomic group such as family were crossed out until only one name or genus. Initially, these character sets were remained. A polyclave key to the five species tables or charts with plant names forming a previously appearing in the indented and matrix with a list of many different character bracketed keys is given below.

Penstemon Prunella Acer Polytaenia Quercus

oklahomensis vulgaris rubrum nuttallii stellata Plants trees - - + - + Plants herbs + + - + - Stems terete + - + + + Stems square - + - - - Leaves opposite + + + - - Leaves alternate - - - + + Venation palmate - - + - - Venation pinnate + + - + + Inflorescences umbels - - - + - Inflorescences panicles + - - - - Inflorescences racemes + - + - - Inflorescences spikes - + - - - Corollas rotate - - - + - Corollas bilabiate + + - - - Ovaries superior + + + - - Ovaries inferior - - - + + Fruits double samaras - - + - - Fruits nuts - - - - + Fruits nutlets - + - - - Fruits capsules + - - - -

If you observe that your unknown plant is the last sentence of this essay to check your an herb with square stems, opposite leaves, identification). spikes, bilabiate corollas, superior ovaries, and As you will note, your unknown plant can nutlets; you will identify it as _?_ (again, see be identified by a single character. As you

Tyrl, R. J. 82 Oklahoma Native Plant Record Volume 10, December 2010 might expect, however, identification by the keys appearing in a flora written inspection in a polyclave key becomes harder specifically for your area or state. as the number of species and the number of Examples of such books are George characters increase. In reality, seldom will a Goodman‟s (1958) Spring Flora of Central single character state be sufficient to identify Oklahoma and Keys and Descriptions for the an unknown. Thus, the process of progressive Vascular Plants of Oklahoma (Tyrl et al. elimination was subsequently simplified by the 2010). The latter is a precursor to the Flora use of cards with “windows” inserted at of Oklahoma which is being written by a various points or their edges punched or consortium of state botanists. If a local notched to reflect different characters and flora is not available, a regional (Flora of the character states. Each card represented a Great Plains 1986) or continental (Flora of single species. The cards were stacked (in any North America North of Mexico 1993+) order) and then retained or eliminated treatment can be used. Remember my depending upon the character state appearing earlier statement about being able to go in the “window” or punched/notched edge anywhere in the world and if a key is until a single card remained and identification available, unknown plants can be was thus accomplished (Hansen and Rahn identified? Keys are available for just 1969; Jones and Luchsinger 1986). about everywhere! Although polyclave keys appeared as early Before beginning to key, spend a few as the 1930s, it was not until the 1960s that moments becoming familiar with your they became widely used (Morse 1971). In the unknown plant. Look at characters such late 1960s and early 1970s, taxonomists began as those cited in the keys given above. to use computer-punched cards in place of Dissect a flower or two. You will find that the window or notched-edge cards (Pankhurst keying is typically faster and easier if you 1974). The advent of computers and the have many of the plant‟s features already ability to incorporate and manipulate a in mind. plethora of characters, character states, and Always read both leads of a couplet and, if species greatly expanded the use of polyclave necessary, again observe the plant keys and today all use computer algorithms carefully before making a decision as to (Simpson 2006). Two approaches are which lead best describes your unknown employed in these computer-assisted keys. plant. Although the first lead of a couplet One is essentially a computerized version of may be applicable, the second may be the punch card system with species being better. eliminated by their incorrect character states Sometimes the leads of a single couplet when compared to the unknown plant. The will be separated by numerous other second is slightly different in that it employs couplets. Use the numbers at the probabilities or likelihood ratios to indicate beginning of the leads to locate them. the species that have been eliminated and Be sure that you read each lead carefully those likely to match the unknown (Jones and and fully understand it. In the indented Luchsinger 1986). and bracketed keys given above, note that Successful Use of a Key—Although a the different characters in the leads are taxonomic key looks intimidating at first, its separated by periods; whereas, semicolons use is quite easy. For individuals who have not are used to separate different states of one used one before, the following suggestions are character, and commas are used for offered. clarity. In other keys, semicolons are used When attempting to identify an unknown to separate characters, and commas are plant, you should use, whenever possible, used to separate character states.

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Be sure that you understand the meanings that you have chosen the wrong lead and of the terms used in each couplet. Use a you need to return to the original couplet glossary; most manuals have one. and take the other lead. Be as careful and accurate as possible in You also will likely encounter a couplet making your observations. Use a that cites a character that your unknown magnifying lens to observe (and discover plant does not have, e.g., fruits or roots. the beauty of) smaller features of the Just ignore it and rely on the other plant‟s surfaces, flowers, and fruits. Use a characters listed in the couplet, or again ruler to measure widths and lengths follow both leads as described above. accurately; don‟t estimate. Sometimes the Satisfaction—As I stated at the beginning of difference between two species is just a this essay, I find it most satisfying to be able few millimeters. to say to an unknown plant, “I now know

Whenever possible, do not base your who you are!” I hope that someday you will selection of a lead on a single observation. have that same feeling of satisfaction. Always try to examine more than one leaf With respect to possibly your first keying or flower or fruit or surface. Remember experiences, were you successful in identifying that plants are living systems and as such the three unknown plants? Based on the sometimes vary in their features. For characters listed (your observations), the first example, one flower may have four petals unknown plant you keyed was Penstemon whereas all the others have five, or a oklahomensis, a species endemic to the state normally alternate-leaved plant may have that flowers from April to June and is an occasional node with opposite leaves. characteristic of the mid to late stages of plant When the name of a family, genus, or succession in prairies. The second unknown species is reached in the key, you should plant was Polytaenia nuttallii, a member of the compare the features of the unknown or carrot family, and typically is plant with the group‟s morphological encountered as scattered plants or small description in a manual and, if available, a populations in dark loamy or clay soils of botanical illustration. If they match, Oklahoma‟s prairies. The third unknown plant identification is accomplished. If they was Prunella vulgaris, a member of the don‟t match, you should reexamine the Lamiaceae or mint family, and generally features of the unknown plant and begin encountered as individual plants or small keying again. Be sure to, again, carefully populations in the moist soils of partially read both leads of each couplet before shaded forests or woods throughout the selecting one. eastern half of the state. You undoubtedly will, at some point, Best wishes for your future keying encounter a couplet for which the experiences! selection of a lead is tenuous. When this happens, you should follow both leads Acknowledgements—I thank Sheila Strawn, and their following couplets. When you Paula Shryock, and an anonymous reviewer arrive at your two “answers,” read the for their assistance in the preparation of this descriptions of both groups in order to essay. determine which best describes your Literature Cited unknown plant. Often, the key will “tell you” whether you have selected the Bather, F. A. 1927. Biological classification: appropriate lead. If the subsequent past and future. Quarterly Journal of the couplets pose leads that are totally Geological Society of London 83:lxii–civ. (In inapplicable to your unknown, it is likely “The Anniversary Address of the

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President,” Proceedings of the Geological E. Sheldonian Theater, Oxford, England Society). (Electronic Resource–Early English Flora of North America Editorial Committee, Books Online; accessed 1 July 2010). eds. 1993+. Flora of North America North of Morse, L. E. 1971. Specimen identification Mexico. 16+ Volumes. Oxford University and key construction with time-sharing Press, New York. computers. Taxon 20:269-282. Goodman, G. J. 1958. Spring Flora of Central Pankhurst, R. J. 1974. Automated Oklahoma. University of Oklahoma identification in systematics. Taxon 23:45- Duplicating Service, Norman, OK. 51. Great Plains Flora Association. 1986. Flora of Ray, J. 1686. Historia plantarum species hactenus the Great Plains. University Press of editas aliasque insuper multas noviter inventas & Kansas, Lawrence, KS. descriptas complectens : in qua agitur primò de Grew, N. 1682. The Anatomy of Plants with an plantis in genere, earumque partibus, accidentibus Idea of a Philosophical History of Plants, and & differentiis : deinde genera omnia tum summa Several Other Lectures, Read before the Royal tum subalterna ad species usque infimas, notis Society. Printed by W. Rawlins for the suis certis & characteristicis definita, methodo Author, London (Electronic Resource– naturæ vestigiis insistente disponuntur : species Early English Books Online; accessed 1 singulæ accurate describuntur, obscura July 2010). illustrantur, omissa supplentur, superflua Hansen, B. and K. Rahn. 1969. Determination resecantur, synonyma necessaria adjiciuntur : vires of angiosperm families by means of a denique & usus recepti compendiò traduntur. punched-card system. Dansk Botanisk Volume. 1. H. Faithorne & J. Kersey, Arkiv 26:1-46. London. Jones, S. B. Jr. and A. E. Luchsinger. 1986. Rivinus, A. Q. 1699. Introductio generalis in rem Plant Systematics. 2nd Edition. McGraw- herbariam: ordo plantarum quæ sunt flore Hill, New York. irregulari pentapetalo. Printed by C. Günther, Lamarck, J. B. de. 1778. Flore francoise; ou, Leipzig, Germany. Description succinte de toutes les plantes qui Simpson, M. G. 2006. Plant Systematics. croissent naturellement en France disposée selon Elsevier Academic Press, Amsterdam, The une nouvelle méthode d'analyse, &, à laquelle on Netherlands. a joint la citation de leurs vertus les moins Stuessy, T. 1990. Plant Taxonomy: The Systematic équivoques en médecine, & de leur utilité dans les Evaluation of Comparative Data. Columbia arts. 3 Volumes. de l’Imprimerie royale, Paris. University Press, New York. Lawrence, G. H. M. 1951. Taxonomy of Tyrl, R. J., S. C. Barber, P. Buck, W. J. Elisens, Vascular Plants. Macmillan, New York. J. R. Estes, P. Folley, L. K. Magrath, C. L. Linnaeus, C. 1736. Bibliotheca botanica recensens Murray, A. K. Ryburn, B. A. Smith, C. E. libros plus mille de plantis huc usque editos, S. Taylor, R. A. Thompson, J. B. Walker, secundum systema auctorum naturale in classes, and L. E. Watson. 2010. Keys and ordines, genera & species dispositos, additis Description for the Vascular Plants of editionis loco, tempore, forma, lingua & c. cum Oklahoma. Flora Oklahoma Inc., Noble, explicatione Fundamentorum botanicorum pars OK. prima. Salomonem Schouten, Amsterdam, Voss, E. G. 1952. The history of keys and The Netherlands. phylogenetic trees in systematic biology. Morison, R. 1672. Plantarum umbelliferarum Journal of the Scientific Laboratories, Denison dfistributio nova, per tabulas cognationis et University 43:1-25. affinitatis ex libro naturae observata & detecta.

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