There seems as if there is a symbiotic relationship between mushroom and fungi. https://botit.botany.wisc.edu/toms_fungi/sep2006.html So according to our data, the field guides are mistaken on this point-- Entoloma should be considered a pathogen of Armillaria. We recommend the name 'Aborting Entoloma' for the common name. Moreover, the carpophoroids should be referred to as Aborted Armillarias.