The William Wallace Denslow Botanical Manuscripts Collection consists of a single volume of manuscripts, chiefly letters, collected from significant botanists and other individuals, including William Henry Brewer, Mordecai Cubitt Cooke, Asa Gray, Isaac Hollister Hall, Thomas P. James, Horace Mann, Edward Sylvester Morse, Charles Horton Peck, George Edward Post, Frederick Ward Putnam, George Thurber, and John Torrey. They were collected by William Wallace Denslow (1826-1868), a druggist who became interested in botany as a means of outdoor exercise to combat tuberculosis. He collected a herbarium of 11,000-15,000 U.S. and European species that Massachusetts Agricultural College purchased in 1870 with a gift of $2000 from William Knowlton.