“Lichens” by Annie Lorrain Smith
Annie Lorrain Smith's textbook “Lichens” has been largely considered by biologists to be a foundational educational text on this particular area of mycology. As a leading scientist in the field at the time of writing this 1921 text, it served as the gold standard for students studying lichens for decades. Though her work has been updated due to the advances science has made in the century since its first publication, Smith's work is still highly regarded as an important part of the history of biology.