What is "ischnoderma"

Ischnoderma is a genus of polypore fungi in the family Fomitopsidaceae. Species in the genus have dark brown and tomentose fruit bodies that become darker brown to black and smooth when mature. The genus, widespread in temperate regions, contains an estimated 10 species. The type species, I. resinosum, is used in mushroom dyeing to produce various shades of brown.