Botany is the science of the study of plants and plant life, a human activity that in some ways predates the existence of humans. Consider that animals have coexisted with plants almost as long as there have been plants. Plants provide the basic food for all animals, and animals would have had to learn to recognize the �good' plants and avoid the �bad' plants. Accordingly, plants and animals both naturally evolved in such a way that they could exploit other species or protect themselves from them. The human race, and indeed all of the animal species past, present, and future would not exist were it not for the many millions of species that make up the plant kingdom, the Plantae. This edition includes 145 entries arranged in A to Z order to help make finding a topic of interest easy. Entries related to basic principles and concepts include fields of study related to the topic; an Abstract that provides a brief, concrete summary of the topic; Key Concepts important to a proper understanding of the topic; a detailed Essay that gives an explanation of the background and significance; and Further Reading lists that relate to each entry.