American botanist particularly interested in pteridophytes, Daniel Cady Eaton was the first professor of botany at Yale College. Born in Fort Gratiot, Michigan, he studied as an undergraduate at Yale where his grandfather, the botanist Amos Eaton, had taught. It was here that he decided to pursue an interest in botany and became well acquainted with the cryptogamic plants, as well as developing an extensive correspondence with other botanists of the time. After his graduation from Yale in 1857 he entered Harvard University where he studied for three years, during which time he was responsible for producing the fern section of A.W. Chapman's Flora of the Southern United States. Eaton also published several papers on the pteridophytes of other countries, including a treatment of 360 species collected by Wright in Cuba and Fendler in Venezuela, which was entitled Filices Wrightianae et Fendlerianae and served as his doctoral dissertation in 1860.

During the American Civil War (1861-1865) Eaton served in the Union Army, working in their commissary department in New York. In 1864, when Yale created the chair of botany, Eaton took it on and two years later married Caroline Ketcham of New York City. Remaining at this institution for the rest of his working life he was also curator of the herbarium at Yale's Department of Biology (YU), where his personal herbarium was deposited until 1968 when they formed the nucleus of the Peabody Museum's herbarium (PM).

Eaton's botanical interests led him to Utah in the 1860s, and he contributed to a number of surveys including the United States-Mexican Boundary Survey, Clarence King's Geological Exploration of the 40th Parallel, George Wheeler's Geographical Surveys West of the One Hundredth Meridian, and the Geological Survey of California. Studying the material from these expeditions he was able to describe many unidentified ferns, particularly from California and northern Mexico, and published several accounts accordingly. Eaton's most important work, however, was his monumental Ferns of North America (1877-1880), which contained the descriptions and colour illustrations of 149 species. Eaton also contributed to Asa Gray's Manual of Botany of the northern United States with an account of the Filices and later he turned his attention to the study of mosses and liverworts.

Sources:
J. Ewan, 1969, A Short History of Botany in the United States
H.B. Humphrey, 1961, The Makers of North American Botany: 78-79.