Gray’s Manual

Gray's Manual, officially titled Manual of the Botany of the Northern United States, from New England to Wisconsin and South to Ohio and Pennsylvania Inclusive, is a seminal work in American botany. First published in 1848 by Asa Gray, it has served as a standard reference for identifying North American flora for generations.12

Asa Gray, often called the "Father of American Botany," was a prolific botanist whose extensive studies unified the taxonomic knowledge of plants in the region. He was also a professor at Harvard University, where he founded the botany department and established the Gray Herbarium. Gray was a supporter of Charles Darwin's theories, advocating for theistic evolution, which posits that God directs the natural world through mechanisms like natural selection.12