The Quest to Preserve and Classify the World's Plants


By Barbara M. Thiers

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“A sweeping history of the origins, development, and future of herbaria and their role in plant consternation.” —The American Gardener

Since the 1500s, scientists have documented the plants and fungi that grew around them, organizing the specimens into collections. Known as herbaria, these archives helped give rise to botany as its own scientific endeavor.

Herbarium is a fascinating enquiry into this unique field of plant biology, exploring how herbaria emerged and have changed over time, who promoted and contributed to them, and why they remain such an important source of data for their new role: understanding how the world’s flora is changing. Barbara Thiers, director of the William and Lynda Steere Herbarium at the New York Botanical Garden, also explains how recent innovations that allow us to see things at both the molecular level and on a global scale can be applied to herbaria specimens, helping us address some of the most critical problems facing the world today.


The Origin of Herbaria

For the past almost six centuries, scientists have been documenting the plants and fungi of the world through herbaria. The basic preparation of the specimens that are housed in an herbarium has changed relatively little over time. But the invention of this simple technology was a key innovation in transforming the study of these organisms from a minor subdiscipline of medicine into an independent scientific endeavor. The herbarium made it possible for scientists to characterize the plants and fungi that grow in faraway places and to understand their diversity on a global scale. Our wealth of specimens today, so carefully preserved through the centuries, is a unique source of data that helps us understand how the world’s vegetation has changed over time and predict how it will change in the future.

Luca Ghini and the Origin of the Herbarium

Evidence suggests that Luca Ghini, a physician and highly esteemed professor, created the first herbarium. The epitome of a Renaissance scholar and teacher, Ghini was born around 1490 near Bologna. His family was part of a growing phenomenon in northern Italy—a middle class composed of merchants and professionals who had the means and time for intellectual pursuits. Forward-looking universities in regional cities such as Pisa, Padua, and Bologna encouraged independent thought, and a continual influx of new ideas and goods came to the region via travelers and traders en route between northern Europe, the Mediterranean region, and the Middle East. Because of the favorable economic and intellectual climate, the Renaissance is said to have come to northern Italy half a century earlier than elsewhere in Europe.

Luca Ghini, from a painting in the Biblioteca Comunale, Imola, Italy. This is a 19th-century copy of an earlier work, which has been lost. It is the only known painting of him.

Ghini gained his medical degree from the University of Bologna in 1527. In addition to his medical studies, he had a broad range of interests, including local flora, fauna, and minerals, which he studied on excursions throughout northern and central Italy. The University of Bologna hired him as a lecturer in medicine after he graduated, and a few years later he introduced a new course to the medical curriculum, one devoted entirely to plants, or “simples,” as plants were often called at the time. This appears to have been the first such course in an Italian university, perhaps in all Europe. Previously, plants were covered in the university curriculum only as part of pharmacognosy, and such courses mostly relied on information that was centuries old.

Renaissance scholars reevaluated existing knowledge, most of which derived from Greek and Roman sources. In doing so they revealed the limits of classical knowledge and began new inquiries. Most of the knowledge about plants up until Ghini’s time came from the soldier and physician Dioscorides, who was born in the 1st century CE (Common Era) in Asia Minor. In his work Dioscorides traveled extensively throughout the Mediterranean region, which gave him the opportunity to study and use a wide range of plants. He summarized the characteristics and medical properties of more than 500 plants in his De Materia Medica (or Peri hules iatrikēs, “on medical material,” in his native Greek), published around 65 CE.

Artemisia absinthium (wormwood), from the Vienna Dioscorides (Codex Aniciae Julianae picturis Illustratus, nunc Vindobonensis), an early 6th-century Byzantine Greek illuminated manuscript of De Materia Medica.

To make sure that his students gained a fuller view of plant diversity, Ghini supplemented his lectures with living plants and encouraged students to make their own observations. Some of the plants he collected in the surrounding countryside; others came from correspondents from as far away as Crete and Syria. Ghini’s concept of teaching through direct observation, rather than depending on classical texts and illustrations, had a direct parallel in other teaching practices of the time, such as the dissection of cadavers to study human anatomy. His course was very popular with students, and within a few years, the subject of botany was a core element of the curriculum, with Ghini as chair of botany. He attracted a circle of formal and informal students who would later spread his ideas and innovations throughout Italy and elsewhere in Europe.

Early in the 17 years Ghini spent teaching his course on plants at Bologna, he had the idea for an innovation that would allow his students to study the important features of plants even in winter when the plants were dead or dormant. This was the herbarium, originally called a Hortus Hiemalis (winter garden) or Hortus Siccus (dry garden). Preparing an herbarium specimen involved placing a freshly gathered plant between sheets of paper in a somewhat naturalistic pose, and then applying pressure to flatten the plant and remove moisture from it. When the specimen was completely dry, it was glued onto the page of a blank book, and the page might then be annotated with a note about the plant’s name, its distinctive features, its medicinal properties, or where it was gathered. If handled carefully and kept protected from moisture, insects, and light, a dried plant specimen could be preserved in this manner indefinitely.

The key features of a plant could be observed in a well-prepared herbarium specimen far more easily than in the books available in the early 16th century. Methods of illustration at that time, except by master artists, were not sophisticated enough to capture the level of detail in plant features needed for precise identification. For example, the illustrations in the Grete Herball by Richard Banckes, the first English-language herbal, published in 1529, show recognizable plant parts (e.g., stems, roots, and leaves) but certainly could not be used to definitively distinguish one species from another. It would be many years until illustrations of the quality of Albrecht Dürer’s Primula would be available to the average botany student.

Grete Herball woodcut of an unidentified plant.

Tuft of Cowslips by Albrecht Dürer, 1526.

Despite his success at Bologna in creating both a plant study curriculum and the herbarium, Ghini was apparently not completely satisfied with the tools he had created for teaching botany—he also wanted to grow a wide range of native and exotic plants for his students to study. In 1544 he took a position at the University of Pisa, which afforded him the opportunity to not only continue teaching about plants but also to create a living resource. The resulting Hortus Simplicium (later the Orto Botanico) was the first known botanic garden. Although it has been moved several times, it still exists, at 5 Luca Ghini Way, very close to the Tower of Pisa. Ghini obtained support for this project from Cosimo de’ Medici (1519–1574), the duke of Tuscany. The hiring of Ghini and the development of the Orto Botanico were part of a larger effort by the duke to enhance science and the arts in Tuscany. A year after the Pisa garden was established, the University of Padua created a similar one. The supervision and development of the Padua garden, which thrives to this day on its original site, was the work of Ghini’s student Luigi Anguillara (c.1512–1570).

The Botanical Garden of Pisa (Orto Botanico di Pisa) today.

Engraving of the Padua Botanical Garden by Giacomo Tomasini in his guide to the garden, Gymnasium Patavinum Jacobi Philippi Tomasini (1654).

Ghini spent 11 years in Pisa, continuing to train a wide range of influential scientists. He returned to Bologna a year before his death in 1556. Ghini was an effective, charismatic, and generous teacher who often maintained a lifelong relationship with his former students. When he died, they exchanged letters expressing great sadness at his passing, and some of his former students raised funds to support the education of Ghini’s son and for dowries for his daughters.

Many of Ghini’s students became well-known pioneers in botany. In addition to his development of the garden at the University of Padua, Anguillara produced Semplici (1549–60), a book series with plant descriptions so precise that the species can be recognized just from his text. Ulisse Aldrovandi (1522–1605) succeeded Ghini at the University of Bologna, where he established a botanic garden and assembled an herbarium of more than 7,000 specimens, the largest of his time; the monotypic genus Aldrovanda is named for him. When Ghini left the University of Pisa, his position went to his student Andrea Cesalpino (1519–1603), for whom the genus Caesalpinia, in the legume family, is named. Cesalpino is most famous for the insightful classification system he introduced in his De Plantis Libri (1583). In this work he groups plants based on their structural features rather than on their medicinal properties or alphabetical order, as had usually been the practice in previous works.

An engraving of Aldrovandi’s cabinet of curiosities. From David Teniers the Younger’s Theatrum Pictorium (1660).

The aquatic insectivorous Aldrovanda vesiculosa (waterwheel plant), the sole member of the genus named for Ulisse Aldrovandi.

Portrait of Andrea Cesalpino by Battista Ricci, held in the Rettorato of the University of Pisa.

Caesalpinia pulcherrima (poinciana), named for Andrea Cesalpino. Plate 5, from Familiar Indian Flowers (1878) by Lena Lowis.

Early in his career Ghini apparently planned to publish a reevaluation of the plants treated in the Materia Medica of Dioscorides. However at some point he decided to turn this work over to his student Pietro Andrea Mattioli (1501–1577), who published his Commentarii in sex libros Pedacii Dioscoridis Anazarbei de Materia Medica in 1544. Ghini not only supplied plants for Mattioli’s consideration but also provided suggestions on the manuscript. The Commentarii was a monumental work that was published in many editions and translated into Latin, French, Czech, and German. Illustrated by handsome woodcuts, it contained descriptions of some plants that were not in Dioscorides’ Materia Medica and were of no known medicinal value. Thus, this publication marks a transition in botanical writings from one focused purely on the medicinal properties of plants to one that considered plants for their own intrinsic interest. Mattioli is eponymized in Matthiola, a genus in the mustard family which contains M. incana (stock), a popular garden plant.

Matthiola incana from Elizabeth Blackwell’s A Curious Herbal, vol. 1, plate 181. Blackwell illustrated plants from the Chelsea Physic Garden in London for this book, creating the drawings, engravings, and coloring for the images. She used the proceeds from the book to secure her husband’s release from debtor’s prison. He repaid the favor by leaving her to live in Sweden, where he was later hanged for treason!

Portrait of Pietro Andrea Mattioli, 1533, held in Genoa’s Musei di Strada Nuova–Palazzo Rosso.

Ghini’s herbarium has not survived, and he did not leave any writings asserting that he was responsible for creating this research tool. Indeed, the act of pressing a plant in paper seems so natural and obvious that is hard to imagine it had a single origin. However, he and his students discuss his collection of dried plants in their correspondence, and the herbaria of several of his students still exist. The botanical section of the Natural History Museum in Florence holds the herbaria of two Ghini students: a collection of approximately 200 specimens prepared by Michele Merini, who was a priest in Lucca, and a larger collection, numbering some 700 specimens, of Cesalpino. Aldrovandi’s herbarium is maintained in the herbarium of the University of Bologna. Many believe that Ghini’s specimens are indeed part of the Aldrovandi collection, but if so, these are not distinguished from those collected by Aldrovandi or others in any way. Guillaume Rondelet (1507–1566), a French physician, ichthyologist, and botanist, studied with Ghini in Pisa for a time and brought the technique of herbarium preparation to France when he became a professor at the University of Montpellier. Through his students, the method spread to Germany, Switzerland, and the Netherlands.

Two other early herbaria of note with a connection to Ghini include the herbaria of Francesco Petrollini, a physician and plant collector from Viterbo, Italy, and Leonhard Rauwolf (1535–1596), a German botanist and one of the earliest explorers of western Asia and Turkey, who studied with Rondelet in Montpellier. Little is known about Petrollini, except that he was a correspondent of Ghini and Aldrovandi, but he is likely the creator of two 16th-century herbaria that still exist today. One is an untitled two-volume set now deposited in the Biblioteca Angelica in Rome, and the other is the En Tibi herbarium, now at the Naturalis Biodiversity Center in the Netherlands. En Tibi, whose full name translates to “Here for You a Smiling Garden of Everlasting Flowers,” is a large, beautifully preserved volume meant to include all known types of plants, probably created for sale or as a gift to a wealthy patron. Rauwolf’s herbarium consists of four volumes of preserved plant specimens, the fourth of which, prepared with extra care, contains his Middle Eastern collections. The pages of this volume have an edging of thicker, colored paper with a faux wood grain, of a type used as wallpaper to cover beams and ceilings. This thicker border raised the space between the pages of the book, creating extra room for the dried plant material. Both the Rauwolf and En Tibi herbaria were at one time owned by Hapsburg Emperor Rudolf II but were stolen from him by the troops of Maximilian of Bavaria in 1620. A short time later, the Swedes looted Maximilian’s treasures during the Thirty Years War (1618–48), and the two herbaria came into the hands of the scientifically inclined Queen Christina of Sweden. She later gave the volumes to her Dutch librarian, and the University of Leiden purchased them after his death in 1689.

A beautifully prepared specimen of a jack-in-the-pulpit, Eminium rauwolffii, from the fourth volume of Leonhard Rauwolf’s herbarium, the specimens for which were collected between 1573 and 1576, on Rauwolf’s trip to western Asia and Turkey.

In 1603, Flemish physician and botanist Adriaan van den Spiegel (1578–1625) published Isagoges in Rem Herbariam, giving detailed instructions on how to prepare an herbarium. The instructions describe a process very similar to that used today, although the recipe for glue used to adhere specimens to paper is different: van den Spiegel’s recipe called for bull’s ears to be boiled with aloe, a piece of steel, and powdered cloves! Today’s herbaria generally use a water-based glue, although some, such as the herbarium of the Conservatory and Botanical Garden of Geneva in Switzerland, use straight pins to hold the specimen to the paper.

A variation on the herbaria created by Ghini and his disciples is the so-called Herbarium Vivum of Hieronymus Harder (1523–1607), a German physician and teacher with no known connection to Ghini. The Herbarium Vivum is a book of dried pressed plants in which the specimen is augmented with a drawing or painting. Sometimes the drawn portion represents missing parts of the plant, such as roots or flowers; in other cases, the habitat for the plant is indicated by a painting of the land surface and perhaps other vegetation at its base. Harder produced 12 volumes of such plant/drawing hybrids, 11 of which are stored in various European institutions. The Herbarium Vivum–style of specimen preservation did not catch on, probably because of the labor and skill involved in the painted portion, but two other examples still exist: one created by Johannes Harder (1563–1606), the son of Hieronymus, and another by Henrik Bernard Oldenland (c.1663–c.1697), a German-born South African physician, botanist, painter, and land surveyor.

A page from En Tibi, showing, among other specimens, a pressed tomato, Solanum lycopersicum, including the fruit, from which the pulp has been removed.

Specimen of violets (Viola) from Hieronymus Harder’s Herbarium Vivum.

Origins of Cryptogamic Collections

The earliest herbaria focused on the dominant group of plants on earth, the vascular plants. United by the presence of specialized conductive cells to transport water and nutrients through the plant (a “vascular” system), this group includes ferns and their relatives (clubmosses and horsetails), the gymnosperms (conifers and related groups), and the flowering plants. However, herbaria also hold preserved specimens of algae, bryophytes, and fungi—or, collectively, cryptogams, an archaic but useful term (from the Greek, kryptos “hidden,” gameein, “to marry”) that refers to the lack of visible reproductive structures, such as a flower, in these organisms. Some would include ferns in this group as well, because they also reproduce by spores, although since they have a vascular system, their structure is more like flowering plants. Early herbaria contained only a small number of cryptogams, and those that were included were usually the larger, more conspicuous species. The Rauwolf herbarium contains a single bryophyte, Conocephalum conicum, a large and extremely common species of liverwort. En Tibi contains four mosses and two lichens, all common and conspicuous European species. Aldrovandi’s herbarium at the University of Bologna contains 22 specimens of algae, bryophytes, and lichens. Today most herbaria include at least some representatives of cryptogamic groups, and some herbaria specialize in them.

Algae is an informal term for organisms that are photosynthetic and usually aquatic. They may range from single- to multi-celled, and they lack true roots, stems, and leaves. Algae have a wide range of reproductive strategies but do not produce flowers and fruits. Instead, they reproduce by sexual or asexual spores. Examples of algae are diatoms, phytoplankton, “pond scum,” and seaweeds. There are an estimated 72,000 species of algae.

Codium tomentosum, a marine green alga.

Sphagnum fallax, a moss found in bogs. Sphagnum is the principal component of peat.

Bryophyte is an umbrella term relating to three lineages of plants, including mosses (Bryophyta), hepatics or liverworts (Marchantiophyta), and hornworts (Anthocerotophyta). All are small, terrestrial, photosynthetic organisms that may grow erect, appressed to soil or rock, or pendent from tree branches. Some bryophytes resemble small leafy plants with distinct leaf and stem-like structures; others are flattened and ribbon-shaped without distinct leaf or stem-like structures. They reproduce by spores that are usually borne on stalks that extend above the level of the plant. There are an estimated 16,000 species of bryophytes worldwide.

Riccia sorocarpa, a thalloid liverwort.

Cookeina tricholoma, an ascomycete fungus. Spores are produced in cells lining the inside of the cups.

Fungi, now recognized as a separate kingdom, are a very diverse group of organisms that includes yeasts, molds, lichens, mushrooms, polypores, and puffballs. Herbarium collections of fungi also usually contain slime molds or myxomycetes, although these are no longer considered to be fungi. Fungi are actually more closely related to animals than plants. Fungi are heterotrophic, which means they absorb their food rather than creating it through photosynthesis. Most fungi are composed of a network of hyphae (narrow, tubular branching filaments), which may be loosely interwoven, as in a mold, or tightly fused together, as in a mushroom. The cell walls of hyphae are made of chitin, the same substance that makes up the exoskeleton of insects. Fungi reproduce by spores. Estimates of the number of species of fungi vary, with some as high as 5 million.

Phylloporus rhodoxanthus. The spores of this mushroom are produced externally from cells lining the surface of the gills, the plate-like structures under the cap.

Cladonia verticillata, a lichen. Lichens are fungi that form a symbiotic association with an alga. The spores are produced from the apothecia, the brown structures atop the gray-green stalks. Lichens grow mainly on soil, trees, or rocks.

For a variety of reasons, 16th-century botanists largely ignored cryptogams. Some of these organisms, like the mushrooms, appear only sporadically. Both mushrooms and algae may decay quickly upon collection and are difficult to preserve. In all the cryptogamic groups, the features that are key for understanding their life histories are too small to view with the human eye alone, which inhibited an understanding of their relationship to other organisms. New methods in glass-making and lens-grinding developed around 1600 made it possible for telescopes and microscopes to become scientific instruments. In 1610, in his Sidereus Nuncius (The Starry Messenger), Galileo reported seeing the mountains of the moon through his telescope; his work created controversy but also great interest in the idea of using lenses to see beyond what is visible to the naked eye. The microscope was technically a more difficult instrument to develop than the telescope, and early versions, such as that developed by the Dutch father and son spectacle-makers Hans and Zacharias Janssen, had a magnification of only about 9×. The microscope developed by Anton van Leeuwenhoek, however, achieved a magnification of 270× and was used by English scientist Robert Hooke in his Micrographia (1665), a book of drawings made through the microscope, including one of the cellular structure of cork (the bark of the cork oak, Quercus suber). The ability to examine the internal structure of plants provided by the microscope played an important role in advancing knowledge of plant diversity. Scientists such as Nehemiah Grew (1641–1712) and Marcello Malpighi (1628–1694) carried out extensive studies on the comparative anatomy and morphology of plants, which, although focused on vascular plants, served to highlight how they differ from non-vascular plants. John Ray (1627–1705), an English naturalist and theologian, transformed Cesalpino’s vision of grouping plants based on natural affinities into a fully realized classification system that was enhanced by the studies of Grew and Malpighi as well as his own observations. In his Historia Plantarum (3 volumes, 1686–1704), Ray pioneered the use of the term “cryptogamia” as a unit of classification, which he divided into four orders: filices (ferns and related groups), musci, algae (which included lichens and liverworts), and fungi.

The Jardin du Roi (Royal Garden), founded in Paris in 1635, was one of the earliest centers for the study of cryptogamic plants. Joseph Pitton de Tournefort (1656–1708) studied the origin of spores in ferns, bryophytes, and fungi, although he did not understand how a single-celled spore differed from a seed, which contains a multicellular embryo and its endosperm, or food supply, and a protective coat. René A. F. de Réaumur (1683–1757) was the first to describe the reproductive structures in the marine alga Fucus (rockweed), and Jean Marchant (1650–1738) in 1713 first described the hepatic genus Marchantia, which he named for his father, Nicolas, who was also a botanist. Marchant made highly accurate drawings of the structure of the plant but still misinterpreted the spores as a very small type of seed.

Etching of scientists at work in the laboratory of the Royal Garden in Paris by Sebastien Leclerc (1637–1714).

The botanic garden in Florence (Orto Botanico di Firenze) was also a focal point of the study of cryptogams, led by Pier Antonio Micheli (1679–1737). Micheli was the first to describe reproduction in fungi, and thus he is often considered the founder of the study of mycology (the study of fungi); he is also known for his pioneering studies of bryophytes and lichens. His Nova Plantarum Genera (1729), with 73 pages of illustrations, was largely devoted to cryptogams; in it, Micheli described about 1,900 plants, including 900 fungi and lichens. His student Giovanni Targioni Tozzetti (1712–1783) succeeded him as director of the Orto Botanico, and the Micheli-Targioni herbarium (now part of the herbarium at the Natural History Museum in Florence) contains about 19,000 specimens. This herbarium is very important as a source of early specimens of cryptogamic groups, although many collections of algae and fungi have not survived. In some cases, the fungi are represented by Micheli’s illustrations. The specimens that do still exist can be difficult to interpret because they are glued on small pieces of paper with very little information about the name or where the specimen was collected.

Never a wealthy man, Micheli depended on subscribers to support the publication of the three volumes of his Nova Plantarum Genera. Among these subscribers was William Sherard (1659–1728), who established the herbarium at Oxford University. When Sherard retired, he chose Johann Dillenius (1684–1747) to replace him. Dillenius, born in Darmstadt, Germany, became the first Sherardian Professor of Botany in 1734. Influenced by Micheli, Dillenius followed in his footsteps as a cryptogam specialist, although he had less of an understanding of the importance of microscopic characters than Micheli, causing him to misinterpret the functions of features such as the sporophyte of bryophytes, which he considered to be a flower. In his Historia Muscorum


  • “With lavish illustrations of places and people; portraits of key players; herbaria specimens; and beautiful, full-color artists’ renderings, this carefully researched, detailed homage to herbaria will appeal to those deeply interested in plant exploration and botany.” —Library Journal

    “A sweeping history of the origins, development, and future of herbaria and their role in plant consternation.” —The American Gardener

    “One of the prettiest books of the season… a lovely coffee table book as well as a serious work on the history of scientific endeavor.” —The Napa Valley Register

    “An enlightening tribute to the mysterious world of Herbaria that is meticulously researched, well organized, and above all accessible.” —Gardens Illustrated

    “This illustrated account of the Herculean efforts of the early botanists in this field is absorbing and enlightening.” —The English Garden

    “At its heart, Herbarium is a compelling reminder of one of humanity’s better impulses: to save things—not just for ourselves, but for posterity… A marvelous book about the ages, for the ages.” —The Nevada Native Plant Society

    Herbarium is sure to enchant anyone who has ever used a flower press or wished to learn more about plant classification, with vintage engravings and woodcuts of ancient plants.” The Free Press

    “Invaluable for any personal library on the history of plants and their future. It is beautifully produced.” —The Financial Times

    “Gardeners with an interest in history will delight in Herbarium.” —Horticulture

    “Thoroughly researched and written in a readable style…this coffee-table book is lavishly illustrated with herbarium specimens, people, places, and maps, it’s one of those glorious books where hours can easily be lost in reading and re-reading.” —RHS The Garden

    “A great book on the history of herbaria…readers interested in biographies and history would find this a great book to read and to add to their library collection.” —Cultivate to Plate

    “This beautifully illustrated history includes not just full-page examples of herbaria, but paintings, prints, maps, and photographs.” —Landscape Architecture

    “This book gives life to botanical collections and is a brilliant work that can be read, understood, and enjoyed by everyone.” —The Journal of the American Botanical Council

    “A journey through the history of botanical collecting… those vivid stories bring specimens to life.”—Plant Science Bulletin

    “This sumptuously illustrated book will delight all botanists, whether their hearts lie in the field or in the herbarium…This is a book that belongs on every botanist’s bookshelf, for the wonderful stories contained within and for the marvelous illustrations of specimens that grace its pages.” The Botanical Society of Britain and Ireland

On Sale
Dec 8, 2020
Page Count
304 pages
Timber Press

Barbara M. Thiers

Barbara M. Thiers

About the Author

Barbara M. Thiers is director of the William and Lynda Steere Herbarium at the New York Botanical Garden, president of the Society for the Preservation of Natural History Collections, and vice president of the Natural Science Collections Alliance.

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