Sac or Cup fungi. Produce sac-like structure called asci where ascospores are produced. 30,000 known species. Septa. Yeasts, powdery mildew, and most blue-green, red and brown molds. Responsible for many food spoilages and plant diseases (Dutch Elm, Chestnut Blight, Ergot Disease (rye plants, toxic to us), Powdery mildew (ornamental trees and bushes). Unicellular yeasts or multicellular cup fungi.