The Genera of Hydnaceae

The family Hydnaceae, as ordinarily defined, is held to include all autobasidiomycetes in which the hymenium is borne upon downward directed spines, warts or folds. As thus defined most of the genera and species are clearly separated from those of re? lated families. Intermediate forms do occur, however, grading into the Polyporaceae on the one hand and the Thelephoraceae on the other. This fact has influenced various attempts to make the boundaries of the family more distinct. Since the time of Fries, our knowledge of the internal structure and reproduction of these fungi has been greatly increased and it has been necessary to make many changes in taxonomic treatment. The lack of agreement in current literature as to what constitutes the most precise or convenient classification is due largely to our still meager knowl? edge of the natural relationships among these fungi. The family has been insufficiently studied and, therefore, any scheme of classification applied to it must be regarded as tentative. The removal of certain genera and species apparently related to the Polyporaceae but included in the Hydnaceae of Fries and his predecessors was suggested first in 1821 by the work of S. F. Gray.1 He erected the Sistotremideae on Sistotrema, Cerrena and Xylodon, and characterized the new family as " thallus leatherlike; hymenium at first meandering, porous, becoming toothed; teeth lamellar, torn." In 1879 Karsten transferred Irpex, Sistotrema and Phlebia to the Polyporaceae. Patouillard in 1900 included Phlebia, Hydnochaete, Lopharia, Sistotrema and species of Irpex among the polypores. Weir and Hubert (1918) comment on the daedaloid character of the young sporophore of Echinodontium.