Cytological Studies on the Process of Armillaria Mellea Infection Through the Sclerotia of Grifola Umbellata Nutrient Source of Sclerotia of Grifola umbellata and Its Relationship to Armillaria mellea Characterization of Sclerotial Formation from Hyphae of Grifola umbellata Discovery and Application of the Companion Fungus Related to Sclerotial Formation from Hyphae of Grifola umbellata