Flask fungi

        Flask fungi derive their name from the fact that their microscopic fruiting bodies are flask-shaped. However, numerous and densely packed fruiting bodies typically occur within a hard, sterile structure called a stroma (plural: stromata), and it is the entire stroma that is readily apparent in nature. The stromata of flask fungi exhibit a wide range of different forms. Some are club-like structures, a few are more or less hemispherical in shape, and numerous examples occur as a cushion-like layer over the surface of a decaying log or stump. Many common flask fungi are decomposers of wood, but others are parasites or pathogens. The fungus that virtually eliminated the American chestnut from the forests of eastern North America is a member of this group.