Ascomycetes (ăs-kō-mi-sē′tēz). A very large group of low plants (Fungi), among which the common mildews may be taken as a type. The mildews are surface parasites and are commonly found covering the leaves of the higher plants with a whitish covering. The leaves of the lilac are very commonly infested by this parasite. To this group also belong such well-known forms as the common blue mould found on bread, fruit, etc.; the common fungus whose subterranean body produces truffles; the fungi which cause the diseases known as black knot of plum and cherry; forms which cause the witch’s broom, peach curl, etc.; while to the same group belong the common cup-fungi and the edible morels; perhaps the common yeast is an ascomycete. The name of the group is derived from the fact that the spores are developed in delicate scacs, each sac being called an ascus; while the spores within these asci are known as ascopores. See Fungi.