A method for preparing permanent stained mounts of pathogenic fungi for microscopic examination.

Many pathogenic fungi may be recognized grossly by their appearance in culture. The more definitive method of identification, however, is through microscopic examination of the structures on which classification depends: the spores and the sporebearing apparatus. The simplest method of accomplishing this is to tease a small fragment of mycelium out of the culture and crush it under a cover slip. This procedure generally disrupts the spores from their attachments and produces a degree of disorder which obs-ures the diagnostic relationships of the spores to the structures on which they are borne. Microcultures prepared on slides or cover slips circumvent this difficulty since such preparations can be examined intact. In this way, disarrangement of thfruiting structure is avoided. The following method is a modification of Riddell (1950) who conceived a means of getting a thin film of fungus to grow over a naked glass surface. The method to be described is simpler and yields permanently stained specimens which are ideal for teaching and research purposes. Although Riddell claimed permanency for his preparations, this has not been our experience with slides stained with cotton blue and ringed with nail lacquer. The quality of the stain gradually deteriorates. Preparations mounted in a lacto-phenol menstruum and ringed with nail lacquer as described by Riddell are only semipermanent.