The first comprehensive application of cladistics to the massive body of data on both living and fossil plants, this book clarifies phylogenetic patterns within and among basal groups of land plants. Ilustrated with line drawings and complete with appendixes detailing the morphology of early fossil plants and their living relatives, this book discusses the implications of its phylogenetic conclusions for understanding the evolution of land plant structure, life cycles, the appearance of groups in the fossil record, biogeographic patterns, and related geological events. In its detailed analysis of the patterns and processes underlying the origin of land plants, the book sheds light on central questions surrounding the initial assembly of terrestrial ecosystems.