On Oct. 6, 1846, prisoner of war Friedrich Adolph Wislizenus ventured into the rocky hills near the secluded Mexican town of Cusihuiriachi to collect some plants. He and his westward exploration party had been captured as the Mexican-American War broke out, but the St. Louis-based doctor and naturalist decided to continue his research during his imprisonment. He pulled up a crimson wildflower, henceforth named Heuchera sanguinea, and hiked back to the village.
He arranged the spindly plant so that once it was dried and mounted on paper, both sides of its leaves would be visible to future botanists, and then he pressed it between sheets of newsprint. After he was freed in the spring of 1847, he carried the dried plant and many others back to St. Louis, presenting it to his friend and fellow doctor Georg Engelmann. And this is where the crisp, rust-colored sample remains — a piece of botanical history, but also an important piece of data, one of almost 6.3 million specimens stored in a forest of manila folders at the Missouri Botanical Garden.