This flora was prepared by 32 people active in floristic and monographic revisions of families and genera represented in Mexico. Their studies have expanded the known ranges of the species, discovered many new species, and placed others in synonymy, demonstrating phytogeographic ties to many parts of the world other than the southern Appalachians. Part 1 covers Sphagnales to Bryales, Part 2 Orthotrichales to Polytrichales.