This is the journal that Oliver Sacks kept during a "fern foray" in Oaxaca, Mexico. Sacks is a fern lover, even though he admits to an even greater passion for club mosses and horsetails. In 1993 John Mickel of the New York Botanical Gardens introduced Sacks to the New York chapter of the American Fern Society (AFS). Consisting mostly of amateur naturalists, AFS meetings were both congenial and passionate, unlike the cold competitiveness of professional meetings in neurology and neuroscience. The New York AFS folks arrange periodic trips to hot spots in the fern world to indulge their passion. In 1999 Oliver Sacks accompanied them on a trip to Oaxaca, which is a veritable paradise of ferns.

Though the trip is only 10 days long, Sacks packs a month’s worth of sights and sounds and meditations into his journal. We learn a lot about the hundreds of species of ferns that range from southern Mexico’s rain forests to the nooks and crannies of its arid central plateau. But the author’s curiosity roams freely and absorbs his new environment. We learn about the origin of chocolate, the history of tobacco, and the archeology of Monte Alban. We learn about the process of distilling mescal in one’s backyard. Most of all, we are introduced to nearly a dozen vivid characters, united in their enthusiasm for fieldwork and ferns.