1911 Encyclopædia Britannica/Ascus
ASCUS (Gr. ἀσκός, a bag), a botanical term for the membranous sacs containing the reproductive spores in certain lichens and fungi. Various compounds of the word are used, e.g. ascophorous, producing asci; ascospore, the spore (or sporule) developed in the ascus; ascogonium, the organ producing it, &c.