DELIMITATION OF HYMENOGASTER-SENSU-STRICTO AND 4 NEW SEGREGATE GENERA

Since Vittadini first described Hymenogaster in 1831, a heterogeneous assemblage of truffle-like Basidiomycetes has been assigned to the gen us. As a consequence, the boundaries of Hymenogaster became inflated e ven beyond Vittadini's original broad concept, and the genus came to r epresent more than one phylogenetic line. This paper clarifies the gen eric limits of Hymenogaster and challenges a prevailing notion that Hy menogaster represents the hypogeous member of a phylogenetic line link ed through Thaxterogaster to Cortinarius. On the basis of both macromo rphological and micromorphological characters of basidiomes, Hymenogas ter sensu stricto is redefined. Selected species are allocated to four new genera: Cortinomyces, Descomyces, Quadrispora, and Timgrovea. A k ey to these genera is provided. Four of the eight original Vittadini s pecies are excluded from Hymenogaster H. rufus (type lost), H. citrinu s (to Gautieria), H. luteus (to Hysterogaster), and H. niveus (to Cort inomyces). The remaining four species have large, thick-walled, broad ellipsoid to fusiform spores bearing a large, cupped hilar appendix an d are designated as the core of Hymenogaster since they include the ty pe species H. bulliardi. Also included with the type are H. olivaceus, H. lycoperdineus and H. griseus. The relationships of these Hymenogas ter species to other fungi are not known, but the spore type does not indicate a close relationship with Cortinarius and Thaxterogaster. The remaining Vittadini species H. niveus is placed in the new genus Cort inomyces by virtue of its smaller, warty spores. Cortinomyces is large ly distinguished from Hymenogaster by having cortinarioid spores. Nume rous other characters, such as peridial pigments and structure, sugges t that Cortinomyces fits into a phylogenetic series with Thaxterogaste r and Cortinarius. Hymenogaster cribbiae, H. effodiendus, H. luteus (n on Vittadini), H. niveus, H. purpureus, H. violaceus, and H. viscidus are recombined to Cortinomyces. Descomyces has distinctive spore morph ology (e.g., a smooth rostrum and ornamentation embedded in the perisp orium) and peridium structure (e.g., two layered and with swollen cell s). This peculiar combination of peridial and spore characteristics al so occurs in Setchelliogaster and in Descolea. It is proposed that Des comyces (with hypogeous angiocarpic basidiomes and a loculate hymenium ) represents the truffle-like form in a phylogenetic series that also includes Setchelliogaster (subhypogeous, pseudoangiocarpic basidiomes) and Descolea (epigeous bivelangiocarpic basidiomes and a lamellate hy menium). Further supporting evidence of this relationship is obtained from examination of mycorrhizae and axenic cultures of these fungi. Sp ecies transferred to Descomyces include H. albellus, H. albus, and H. javanicus. H. albellus and H. albus are maintained as separate species , the former is considered to include collections having a polycystode rm (epithelium). Quadrispora includes species with assymetrical spores that adhere in tetrads after release from the basidium. H. oblongispo rus is recombined into the new genus, and Q. musispora is described as new. The relationships of Quadrispora to other fungi are not known. F inally, Timgrovea is proposed to accommodate species with reticulate s pores, T. reticulatus, T. macrosporus, T. subtropicus, and T. ferrugin eus from Australia, and T. kwangiensis from China. The relationships o f Timgrovea probably occur outside the Cortinariaceae. A possible rela tionship of Timgrovea to the Boletaceae is discussed.