Monocotyledons ('monocots'), though comprising only one fourth of all flowering plant species, are economically and ecologically crucial. In families such as the grasses and palms, they include some of the most valuable plant species to humanity. Numerous monocot species have great ornamental value due to their spectacular flowers or characteristic structural features. They range in size from the smallest flowering plants, Wolffia arrbiza, little more than 1 mm across, to massive palm trees up to 40m tall. Monocot species occur in arctic regions, wet tropical forests, and deserts, and have a wide range of life forms, including floating and rooted aquatic plants, geophytes, epiphytes, and lianas. The book includes reviews and reports of current research by the world's leading specialists, based on presentations made at the Fourth International Conference on the Comparative Biology of the Monocotyledons and the Fifth International Symposium on Grass Systematics and Evolution, held in Copenhagen in 2008.