The Genus Diaporthe Nitschke and Its Segregates by Lewis E. Wehmeyer is an in-depth analysis and organization of the genus Diaporthe, aimed at rectifying the confusion caused by scattered and incomplete descriptions in mycology. This monograph emphasizes the importance of systematic, comparative studies over merely describing new species. Wehmeyer reorganizes existing collections and data into a coherent whole to aid further research. This work highlights the genus Diaporthe, describing its taxonomy, morphology, and phylogeny. Diaporthe species are characterized by their stromatic forms, varied spores, and differentiated stromata, often with blackened zones in the substratum. The book also discusses the host-specific variations and ecological distribution of these species. The significant body of research includes detailed morphological descriptions, taxonomic keys, and illustrations of the genus Diaporthe and its closely related genera such as Apioporthe, Diaporthopsis, Diaporthella, and Cryptodiaporthe. This critical compilation serves as a foundation for future studies, providing essential insights and a structured approach to understanding the biology and taxonomy of these fungal groups.