Phytotaxa 348 (2): 159–161 http://www.mapress.com/j/pt/ Copyright © 2018 Magnolia Press Correspondence PHYTOTAXA ISSN 1179-3155 (print edition) ISSN 1179-3163 (online edition) Accepted by Masoomeh Ghobad-Nejhad: 28 Mar. 2018; published: 27 Apr. 2018 https://doi.org/10.11646/phytotaxa.348.2.12 159 Septal-pore-associated structures of Hysterangium clathroides and Hysterangium nephriticum (Hysterangiales, Basidiomycota, Fungi) PIOTR MLECZKO 1 , BARTOSZ J. PŁACHNO 2 & PIOTR ŚWIĄTEK 3 1 Department of Plant Taxonomy, Phytogeography and Paleobotany, Institute of Botany, Jagiellonian University in Kraków, 3 Gronosta- jowa St., 30-387 Kraków, Poland, piotr.mleczko@uj.edu.pl 2 Department of Plant Cytology and Embryology, Institute of Botany, Jagiellonian University in Kraków, 9 Gronostajowa St., 30-387 Kraków, Poland, bartosz.plachno@uj.edu.pl 3 Department of Animal Histology and Embryology, University of Silesia in Katowice, 9 Bankowa St., 40-007 Katowice, Poland, piotr.swiatek@us.edu.pl The hyphae of Basidiomycota and Ascomycota are divided into compartments by the cross-walls (septa). In mushroom- forming fungi, members of subphylla Pezizomycotina O.E. Erikss. & Winka (Ascomycota) and Agaricomycotina Doweld (Basidiomycota), the septa are associated with specific intracellular structures, which play a role in maintaining the integrity of hyphae in case of injury but also in cell differentiation (Webster & Weber 2007, Moore et al. 2011). In basidiomycetes, these structures may also be involved in certain intracellular processes and the formation of sporocarps (Van Peer et al. 2010, Moore et al. 2011). In this fungal group they are the reticulum-connected and -derived membranous structures called septal pore caps (SPC) or parenthesomes, associated with a dolipore (Moore 1985, 1996, van Driel 2007). The pores may also be occluded by a range of materials of different form. The septal-pore-associated structures may differ considerably between species of different evolutionary lineages. This quality was used as a differentiating factor in the taxonomy at both species and higher-order levels (Lutzoni et al. 2004, McLaughlin et al. 2009). The septal pore complex morphology in Agaricomycotina was recently summarised by Van Driel and co-workers (2009). In the review, the authors emphasize the importance of the ultrastructure of septa and septum-associated SPCs as taxonomic markers and draw conclusions on the evolution of these structures in this group of Basidiomycota. They also point out the gaps in the currently held knowledge in this area, which include the ambiguous ultrastrucural data and the lack of information on the structure of SPC in certain groups of fungi. One of them is the Hysterangiales K. Hosaka & Castellano order, a group closely related to Phallales E. Fisch. within the Phallomycetidae K. Hosaka, Castellano & Spatafora lineage (Hosaka et al. 2006). The aim of this paper is to bridge the information gap through description of the septal pore caps in Hysterangium clathroides Vittad. and H. nephriticum Berk., two species of the type genus of Hysterangiales. The material for the study comprised of sporocarps and the associated rhizomorphs of Hysterangium clathroides (Fig. 1) and H. nephriticum (Fig. 2), collected in Western Carpathians, Poland, in the Beskid Żywiecki (coll. date: 1.08.2013, lg. Ryszard Rutkowski, in a mixed fir-spruce forest) and in the Pieniny Mts. (coll. date: 27.07.2017, lg. Piotr Chachuła, in a mixed beech-fir forest), respectively. Sporocarps were identified according to Montecchi & Sarasini (2000) and Castellano (1990). Exsicates are stored in the Herbarium of the Institute of Botany, Jagiellonian University in Kraków (H clathroides: KRA F- 2013-95, H. nephriticum: KRA F-2017-8). Fragments of peridium and rhizomorphs were used for TEM observations. The material was fixed and prepared as in Płachno et al. (2016). The ultrathin sections were examined using a Hitachi H500 electron microscope at 75 kV in the Faculty of Biology and Environmental Protection, University of Silesia in Katowice. The septa were observed in hyphae in different stages of maturity. The dolipores were typical and well developed, up to 506 nm thick, surrounded by a continuous membrane, with a central pore occluded by an electron-dense material at both sides (Fig. 3). An electron-dense line was observed running centrally across the pore in addition to rays extending perpendicularly from this line. The SPCs were of a continuous type, ca. 55–60 nm thick, and composed of nine layers (Figs 3, 4). No evidence of the presence of perforations in the SPCs membranes were observed in any of the septa analyzed. Several SPC morphological types have been described in fungi, with two of them, the perforate and imperforate, being characteristic of Agaricomycetes Doweld and Dacrymycetes Doweld within Agaricomycotina (Van Driel et al. 2009). However, more recent and detailed studies have revealed that more types should be distinguished within this group: imperforate to uni-perforate, regularly perforate, irregularly perforate, and unstable perforate SCPs (Hibbett et al. 2014). The last type is most probably characteristic of Phallomycetidae species, and all the species investigated so far were found to possess such SPCs although only a few species from the Aseroë Labill., Clathrus P. Micheli ex L., Phallus Junius ex L. (Phallales), Geastrum Pers., Sphaerobolus Tode (Geastrales K. Hosaka & Castellano), Gomphus Pers., and Ramaria Holmsk.