This is the first publication of the 170 letters written by the Abbé Dominique Chaix to Dr. Dominique Villars between 1772 and 1799, when they were collaborating on the publication of the first flora for the old province of Dauphiné. The letters reveal the uncertainties of plant classification in the late 18th century, but, more generally, the penetration of the Enlightenment into a remote, alpine region of France. Both botanists were of recent peasant origin, invading, albeit deferentially, an intellectual field, traditionally the monopoly of their social betters. The letters also document the enthusiasms, anxieties, and perils of rural clerical life during the French Revolution, and give occasional evidence about the deforestation of the mountains.