phacidium

from The Century Dictionary.

• noun A large genus of discomycetous fungi, type of the family Phacidiaceæ, having ascocarps embedded in the surface of the host, the upper covering rupturing at maturity in an irregular manner. The spores are hyaline and unicellular. About 70 species are known. P. abietinum occurs on the fir needles in Europe and America.