Sertulicium Spirin, Volobuev & K.H. Larss., gen. nov.
Index Fungorum number: MB 833941; Facesoffungi number: FoF
Etymology: Sertulum (Lat., noun)—a small chaplet. Basidiocarps effused, very thin to rather thin (usually up to
0.1 mm thick), pruinose or waxy. Hymenophore smooth. Hyphal structure monomitic; all hyphae clamped, CB (+). Cystidia mostly absent, hyphidia rarely present, simple. Basidia clavate, with 4–6 sterigmata, normally not collapsing at the apex. Basidiospores thin-walled (but the wall distinct), narrowly ellipsoid to cylindrical, inamyloid, acyanophilous, contents homogeneous and CB (+). On rotten wood of decid- uous trees and conifers.
Generic type: Corticium niveocremeum Höhn. & Litsch.
Morphological differences between Sertulicium and Sistotremastrum s. str. cannot be easily grasped due to the extreme anatomical simplicity of their representa- tives. Nevertheless, some distinguishing characters are indicated here awaiting more in-depth analysis in the future. First, all but one Sertulicium spp. are extremely thin fungi consisting of a few subicular hyphae and the overlying subhymenium. The subicular hyphae are scattered; i.e., they do not produce hyphal strands so characteristic for most Sistotremastrum s. str. species studied by us. The only exception is Sertulicium granuliferum, having the most elaborate fructifications in the genus. Its basidiocarps start their development as radially arranged hyphal bundles becoming quickly cov- ered by randomly arranged hyphae and finally indiscern- ible. In contrast, in Sistotremastrum s. str. subicular hy- phal strands can be detected even in senescent basidiocarps if hyphae are not totally collapsed. Second, basidia in all Sertulicium spp. bear up to six sterigmata while at least some Sistotremastrum s. str. species are strictly four-sterigmatic. Moreover, apical parts of basidia in the latter genus often collapse, and hymenial cells of this kind dominate in well-developed and in senescent basidiocarps. Such apically collapsing basidia may occur in Sertulicium spp., too, but they are as a rule rare. Finally, all Sertulicium spp. have a smooth hymenial surface while about a half of the currently known Sistotremastrum spp. have a hydnoid hymenophore.