Plants feed us, clothe us, provide us with the oxygen we breathe, and buffer our environment against change. In short, plants make life possible. Yet scientists estimate that over 10 percent of the world’s approximately 300,000 plant species are at risk of extinction, and huge swaths of tropical forests and other plant communities are being decimated daily. This book surveys the world’s green plant diversity, from green algae through flowering plants. It presents the fascinating natural history and diversity of green plants in a taxonomic and evolutionary context. The book also asks and answers the questions: Why are there so many plant species in the world? And how can so many plants grow together in a given patch of prairie, forest, or wetland? Through the study of plant diversity, students will gain an appreciation of the natural world far beyond the classroom and the study of botany, to an understanding of how our actions impact the world around us. Plant Diversity is suitable as a supplementary text for a biology course or as recreational reading for the interested student.