Underside smooth or wrinkled/roughened <Stereum etc> species

In essence the underside of a fruitbody in this sub-group is smooth, though there may some wrinkles or occasional warts.

Most sightings of such fruitbodies will belong to the genus Stereum.

In that genus the effused-reflexed (or sheet+shelf) growth form is common. Such a fruitbody starts its development as a flat, sheet-like growth on a downward facing surface (e.g. the lower side of a leaning trunk or of a fallen branch lying on the ground). After a while the upper edge of this sheet-like growth turns out from the wood to form a horizontal shelf.

In some effused-reflexed Stereum species the shelf may curve downwards and, in those species with small fruitbodies, the fruitbody may resemble an upside down cup, its side attached to the wood and you may at first look for them amongst the cup-like fungi. However, all species of Stereum will be put here and there is a warning to that effect in the overview of the cup-like fungi.