An improved fungal mounting technique for Nomarski microscopy

Abstract

The 'sellotape technique' of Butler and Mann (1959) with lactophenol cotton blue stain is widely used in these laboratories for the production of non-permanent fungal mounts for class examination using bright field microscopy. The technique allows very little disturbance of fungal structure for identification and taxonomic work. The major drawbacks of this technique for permanent mounts are the fact that the tape itself is not inert and the adhesive reacts with the lactophenol forming droplets which cover the field of view (Onions et al., l98l). The stressed nature of the tape also gives rise to problems due to interference patterns during Nomarski microscopy. The increasing use of diflerential interference contrast(Nomarski) microscopy in mycological studies prompted a re-evaluation of techniques used in the preparation of fungal mounts. Other types of nonstressed tapes were found but these proved not to be sticky enough to pick up fungal structures from agar media cleanly and without undue damage. The technique described below uses a silicone based adhesive in conjunction with the slightly modified polyvinyl alcohol mountant of Salmon (1954), updated by Omar et al. (1918), and represents a modification and improvement of the technique described by Bretz and Berry (1964).