Specimen Press

A botanist presses specimens of plants for study and comparison with other specimens of similar species that have been gathered at different times and places, worldwide. Meriwether Lewis knew that his studies in the field would be backed up by the most prominent cabinet—that is, laboratory—botanists of his day.

Plant Press

a plant press

Among them was to be Frederick Pursh (1774-1820), a German botanist whom Lewis hired at Philadelphia in May of 1807, paying him a total of seventy dollars to assist him in preparing his collection for a planned but never written publication of his own.1 Pursh examined 124 of Lewis's specimens, verified or corrected Lewis's descriptions, wrote many new "diagnoses," and assigned names to the species that were new to science.2 He also painted water colors of thirteen of those, and in 1814 included them all in his two-volume Flora Americae Septentrionalis (FLO-ruh a-MAY-ree-kay sep-TEN-tree-oh-NAL-iss; Plants of North America).

A botanical collector like Meriwether Lewis had to begin the process of preserving his specimens as soon as possible after picking them, to forestall wilting and shriveling. The field botanist must place the leaves, stems, flowers, fruits, and roots on sheets of mounting paper with the utmost care and foresight. The whole point is to preserve every specimen in a way that will enable the cabinet botanist to examine minute details that will facilitate the writing of a definitive analysis of each specimen. Immediately, each mount must be covered with a sheet of soft, loose-textured, highly absorbent bibulous (Latin for "drinking") or "blotter" paper, in order to draw all moisture out of the specimen. In some cases a discreet dissection may be necessary to provide maximum value to the collection. A memorandum is added containing the date and place the specimen was found, perhaps with a very brief description including known uses of the plant, and the collector's name. Stacks of specimen mounts and blotter papers are weighted down or tied together tightly, then monitored frequently until the drying is complete.

The Corps of Discovery's Lewis was a conscientious field botanist. The collector must monitor the drying process carefully including daily awareness of ambient temperature and humidity to be sure the specimens remain intact and free from mold or decay and to guard against invading insects. If possible, the specimen must be exposed occasionally to warm sunlight and dry air. This must have been a serious challenge to Lewis under the field conditions he endured from day to day. It certainly was at Fort Clatsop, where the average daily humidity probably ranged from 70 to 90 percent, and it rained all but six days between their arrival at the coast and their departure on March 23. In short, until the specimens are deposited in a secure collection facility known as a herbarium, botanizing is a tedious, time-consuming procedure which demands close, periodic attention.

  • 1. Jackson, Letters, passim.
  • 2. It is estimated that seventy or seventy-five specimens were new to science when Lewis collected them. Pursh honored Lewis by naming four new species after him: Linum lewisii (LEE-noom loo-WEE-see-eye; Lewis's wild flax), Mimulus lewisii (MIM-oo-luss loo-WEE-see-eye; Lewis's monkey flower), Philadelphus lewisii (fill-uh-DELL-fuss loo-WEE-see-eye; Lewis's syringa–si-RING-guh); and Lewisia rediviva (reh-dee-VEE-vuh; bitterroot).