ABSTRACTScytinostroma galactinumis a species complex and contains two inter-incompatible species with similar basidiocarp and cultural morphology. The two species can be distinguished by substrate and isozyme analysis.Scytinostroma galactinumoccurs on woody gymnosperms and occasionally on angiosperms throughout North America.Scytinostromaprotrusum, comb, nov., is found on angiospermous wood. Two subspecies of S.protrusumare recognized based on physiological and distributional data.Scytinostroma protrusumsubsp.septentrionale, subsp. nov., occurs primarily in the northern United States and is less tolerant of gallic acid than S.protrusumsubsp.protrusum, which occurs in the southern United States. Basidiocarp and cultural descriptions ofS. galactinumare provided.Scytinostroma protrusumis tetrapolar and multiallelic at the mating type locus.