Pennsylvania, a state of diverse geography and geology, is rich in flora. The second edition of The Plants of Pennsylvania identifies the nearly 3,400 species of trees, wildflowers, ferns, grasses, sedges, aquatic plants, and weeds native to or naturalized in the Commonwealth. Retaining the clearly written identification keys and descriptions that made the first edition such an essential reference, this new edition has been reorganized to reflect recent advances in our understanding of plant relationships. Families and genera are listed in a sequence determined by current studies of plant molecular genetics, thus providing new insights for the study of botany. In addition, species have been added to the book as a result of new discoveries. The botanical illustrations of Anna Anisko continue to complement the descriptions and add an element of beauty to the volume. Developed in conjunction with the Pennsylvania Flora Project, and compiled by botanists at the Morris Arboretum, the official arboretum of the Commonwealth of Pennsylvania, the second edition of The Plants of Pennsylvania is the authoritative guide to Pennsylvania's plant life. It will be indispensable to taxonomists, conservationists, ecologists, foresters, land planners, teachers, agricultural county agents, students, and amateur naturalists.