This new fourth edition has been completely revised and updated, covering all aspects in the field of plant sciences including biochemistry, plant physiology, cytology, ecology, genetics, evolution, biogeography, earth history, and earth sciences. Over 500 new entries, including Rosales, physical dormancy, menthol, and codeine, enhance the dictionary's coverage of botanical terms, key drugs and medicines derived from plants, and plant orders, families, and genera. It also explains many ecological terms, and expands beyond plants to describe fungi and bacteria and how they affect plants. Numerous appendices include Plant Classification and SI Units, with new timelines showing important moments in plant evolution. For ease of use, vernacular plant names have been transferred to an appendix, fully cross-referenced to the A to Z entries. The dictionary's dedicated companion website points to recommended web links and additional resources. The most up-to-date dictionary available on its subject, this is an essential resource for students of plant sciences and amateur botanists, as well as an entertaining and valuable guide for the plant enthusiast.