The Process of Collecting, Preserving, Recording, and Naming the Plants
Lewis used methods of other botanists of the day to preserve the plants. To help determine a plant’s identity, specimens were collected with as many parts as possible, including leaves, stems, roots, flowers with stamens and pistils, hairs and spines, fruit, and seed. The time of year determines which plant parts are available.
To facilitate drying, specimens are carefully laid out between sheets of absorbent paper, such as blotting paper or newsprint. The sheets are then placed in a press, which may simply be two pieces of wood, perforated to let moisture escape, and held tightly together with straps. Many specimens can be placed in one press. Once dry, they are removed to an airtight and watertight storage container.
The collector must also label each specimen, indicating where and when it was found, with observations on the habitat. Unfortunately only 34 labels in Lewis’s handwriting remain today. They were written on mauve blotting paper. The plant specimens were all removed at a later date from their original sheets. Many now bear labels in the handwriting of the young German botanist Frederick Pursh, who very likely copied Lewis’s notations onto his own labels. Pursh had been recommended to Lewis as the best person to write formal botanical descriptions of the plants that had been collected.
In 1811 Pursh published his work on North American plants, Flora Americae Septentrionalis, based extensively on the plants that Lewis had collected. He assigned scientific names in Latin to the plants, often honoring Lewis and Clark. Lewisia rediviva for bitterroot, Clarkia pulchella for ragged robin, and Linum lewisii for perennial flax are just a few.
Herbarium Specimens from the Lewis and Clark Expedition
In preparation for the expedition Thomas Jefferson sent Meriwether Lewis to Philadelphia to study with various experts, including Benjamin Smith Barton, professor of botany at the University of Pennsylvania and author of the first botany text published in the United States. Lewis took Barton’s text and other reference books on the expedition. Probably it was Barton who taught Lewis how to collect, press, and dry specimens so they could be preserved and brought back to Philadelphia and studied by experts.
Some of Lewis’s plant specimens were shipped back after the first winter in 1805. The rest were carried across the continent. Not all the plants that Lewis collected have been preserved. All those gathered during the spring and summer of 1805 and stored in a cache at the base of the Rocky Mountains were destroyed by rising springtime waters. Others were lost in transit, were destroyed by insects or mold, or disintegrated over time. Today there are 226 specimens in the Lewis and Clark Herbarium at the Academy of Natural Sciences in Philadelphia.
THE HERBARIUM OF SMITH COLLEGE
An herbarium is either a collection of pressed, dried specimens of plants, usually labeled and arranged in an orderly manner, or a room, building, or even a larger institution where collections of this sort are kept. Herbaria (of either sort) are important because as they serve as reference collections to aid in plant identifications, as repositories that document botanical studies, and as sources of information in themselves, serving quite often as evidence of the plant life of their surrounding regions. The Herbarium of Smith College has been in existence at least since 1886, little more than a decade after the founding of the College. It now possesses a nearly complete collection of the flora of the Connecticut Valley in Massachusetts dating back to that era as well as thousands of specimens collected later from throughout New England, the nation, and indeed the world. The Smith College Herbarium is now located on the fourth floor of Burton Hall and is used in teaching and research. The specimens in this case were selected from the Smith herbarium because they represent plants observed in the West on the Lewis and Clark expedition.