SUMMARY: The development in culture of a stromatal rind of Sclerotinia fructicola was studied with a light microscope and the surfaces of stromata of the brown rot fungi grown on agar cultures and on fruits were examined with a Stereoscan electron microscope. The hyphae on the surface of some stromata retained their shape, while on other stromata a crust of thickened, collapsed hyphae developed over the outside. In some places rounded cells were seen below the gaps in the crust. The deposit of a melanin-like pigment around and in the walls of exposed stromatal hyphae may possibly increase the resistance of these hyphae to drying and be of importance in survival of the brown rot fungi.