What is the X in X-mas?
"sac in certain fungi," 1830, Modern Latin, from Greek askos "leather bag, wine skin," of unknown origin.
ascus as·cus (ās'kəs)
n. pl. as·ci (ās'ī', -kī')
A membranous, often club-shaped structure in which typically eight spores are formed through sexual reproduction of ascomycetes.
Plural asci (ās'ī', -kī')
A membranous, often club-shaped structure inside which ascospores are formed through sexual reproduction in species of the fungi known as ascomycetes. The ascus is unique to ascomycetes and distinguishes them from other kinds of fungi. Asci are formed when two hyphae that are sexually compatible conjugate. Each ascus typically develops eight ascospores. Asci swell at maturity until they burst, shooting the ascospores into the air.
a saclike structure produced by fungi of the phylum Ascomycota (sac fungi) in which sexually produced spores (ascospores), usually four or eight in number, are formed. Asci may arise from the fungal mycelium (the filaments, or hyphae, constituting the organism) without a distinct fruiting structure, as in the leaf curl fungi; it may arise within a fruiting structure (ascocarp) that may be exposed, as in the molds and powdery mildew fungi; or it may be imbedded in a compact structure (stroma), as in the ergot and black knot fungi. In the case of yeasts, a single cell converts to an ascus.