wpe4.jpg (38363 bytes)    

Hypomyces hyalinus parasitizing   Amanita rubescens

Hypomyces hyalinus is a species of the Ascomycota.  It parasitizes the fruitbodies of the gill fungus Amanita causing abnormal development.  The Amanita mushroom remains whitish and becomes malformed;  the cap does not develop normally and gill development is suppressed. The tiny fruitbodies (perithecia) of the parasite are embedded in the surface of the malformed fruitbody.

The malformed mushroom is now part host (the Amanita mushroom) and part parasite (the Hypomyces ) and is referred to as a pseudostroma ( =false stroma).  A true stroma such as is found in Xylaria (click here ) is made up entirely of the  fungus.