100 Species #93: Abortive Entoloma
These abortive Entoloma mushrooms Entoloma abortivum/Armillaria gallica emerged among others in profusion around the roots of a Norway maple bordered by the side yard fence and the southwest retaining wall.
Entoloma is a genus of fairly nondescript medium-sized neutral-colored gilled mushrooms that includes both edible and poisonous species. Most are probably mycorrhizal, and are found on open ground near trees. E. abortivum sometimes produces sterile, misshapen, puffball or cauliflower-like fruiting bodies, in association with another the fungus species Armillaria gallica. You may recognize that second fungus genus to be that of the honey mushrooms--the previous species in this project was the ringless honey mushroom Armillaria tabescens.
When it was discovered that these two fungi species interacted to produce "aborted" fruiting bodies, it was assumed that the honey mushroom--known to be a parasite of tree roots--was parasitizing the Entoloma. In 2001, mycologist Tom Volk demonstrated that the "carpophoroid" bodies were actually deformed honey mushrooms, and that Entoloma should be considered a pathogen of Armillaria. A parasite of a parasite.
Surprisingly, this particular species duo is not rare. In fact, these were some of the first mushrooms we discovered in the very first mushroom class I ever took (Habitat in 1998 I think). They appear regularly in various places on Drumlin Farm, and I have found them in other places as well. I was still surprised to find them in my new yard. I'm only counting it as one species, since I'm still ahead of schedule.
http://botit.botany.wisc.edu/toms_fungi/sep2006.html