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.
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. Pursh examined 124 of Lewis's specimens, verified or corrected Lewis's descriptions, assigned names to the ones that were new to science,1 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 field botanist places the leaves, stems, flowers, fruits, and roots between pieces of soft, loose-textured, highly absorbent paper. A memorandum is added containing the date and place the specimen was found, a brief description, sometimes including known uses of the plant, and the collector's name. The pages are weighted down or tied tightly together to prevent the leaves and stems from curling.
The collector must monitor the drying process carefully to be sure the specimen remains intact and free of mold or decay, and to guard against invading insects. If possible, the specimen must be exposed occasionally to warm sunlight and dry air, and the papers changed, to prevent mold. 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.
1. 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).