Although they are among the most abundant of all living things and provide essential oxygen, food, and shelter to the animal kingdom, few books pay any attention to how and why plants evolved the wondrous diversity we see today. In this richly illustrated and clearly written book, Karl J. Niklas provides the first comprehensive synthesis of modern evolutionary biology as it relates to plants. After presenting key evolutionary principles, Niklas recounts the saga of plant life from its origins to the radiation of the flowering plants. To investigate how living plants might have evolved, Niklas conducts a series of computer-generated \"walks\" on fitness \"landscapes,\" arriving at hypothetical forms of plant life strikingly similar to those of today and the distant past. He concludes with an extended consideration of molecular biology and paleontology. An excellent overview for undergraduates, this book will also challenge graduate students and researchers.