MEIOSIS, SEPTAL PORE ARCHITECTURE, AND SYSTEMATIC POSITION OF THE HETEROBASIDIOMYCETOUS FERN PARASITE HERPOBASIDIUM-FILICINUM

Meiosis, spindle pole body cycle and septal pores in Herpobasidium fil icinum were examined using light and electron microscopy and compared with findings in the Uredinales and other simple-pored heterobasidiomy cetes. The septal pore apparatus in Herpobasidium filicinum is rustlik e, and the nuclear characteristics are also similar but not identical to those found in the Uredinales. Some details, such as the spindle po le body behaviour at prophase, the presence of a complete wrapping of endoplasmic reticulum surrounding the nucleus during division, the ext ension of the spindle pole body into the cytoplasm during division, an d the nucleolus behaviour, distinguish Herpobasidium filicinum from th e rusts. On the other hand, nuclear division and spindle pole body cha racteristics in Herpobasidium filicinum show some features common with Cryptomycocolax abnorme. However, Helpobasidium filicinum shares more important nuclear features with Pachnocybe ferruginea, Eocronartium m uscicola, Helicobasidium mompa, and Helicobasidium brebissonii than wi th the Uredinales or Cryptomycocolacales. Apart from the phylogenetic implications of the ultrastructural data, the most interesting observa tion in the present work is the unusual type of meiosis. No evidence f or meiosis II was found in basidia of Herpobasidium filicinum. Instead , the genesis of the interphase I spindle pole body in Herpobasidium f ilicinum is essentially identical to the basidiomycetous postmeiotic a nd intermitotic spindle pole body duplication.