Endophytic fungi are common and diverse in plants. Yet the nature of their interactions with host plants, and how these interactions cascade upward to communities and ecosystems are largely unknown. In the first book of its kind, Gregory P. Cheplick and Stanley H. Faeth provide a new synthesis of existing studies of endophyte-grass symbioses within the context of modern ecological and evolutionary concepts. The authors present a large body of research covering a range of topics including the effects of endophytes on host growth, physiology, reproduction, and competitive ability in a variety of grasses and environments. Clearly and engagingly written, this long-needed book highlights the most essential aspects of symbiosis ecology and evolution while suggesting avenues for significant future research.