Hemlock Reishi (Ganoderma tsugae) closely resembles another tree-growing shelf fungus called Red Reishi (G. lucidum). Fruiting bodies of Hemlock Reishi usually have a dark red/brown stem, though they are occasionally stemless. In the photo above, the stem is mostly hidden from view, but stems can be seen on several of the fungi pictured in Quiz #112. Young fruiting bodies have a red-to-orange cap with a white margin and a white pore surface. Once mature, caps turn a uniform deep red and often become coated with spores (see below).
As you might guess, Hemlock Reishi typically grows on Eastern Hemlock (Tsuga canadensis), unlike Red Reishi which typically grows on hardwoods. Both species are said to have similar medicinal properties (for details on this, read chapter 7 of Mushrooms for Health: Medicinal secrets of northeastern fungi by Greg Marley).