Book excerpt: The variety of the mycological world is far greater than most people imagine. Some fungi kill trees and ravage crops, and pathogenic fungi can infect animals and even humans. But fungi also play crucial roles in ecosystems. They act as agents of wood decay in forests, and symbiotic relationships with mycorrhizal fungi are vital to many plants. In this Very Short Introduction Nicholas P. Money explains the essential functions performed by fungi, the importance of studying them to contain fungal diseases, and how fungi are being used in agriculture, biotechnology, and medicine. -- from cover flap.