Plastic sectioning for light microscopy of Pyrenomycetes.

In preparation for light microscopy, ascocarps of Sordaria fimicola Ces. & DeNot. were embedded in Spurr's medium and sectioned at 1-1.5 mum on an ultramicrotome. Sections were floated on Giemsa staining solution at 60 C for 10-30 min, washed in distilled water, affixed to slides by drying, and mounted in immersion oil. Best preservation of the delicate sterile tissues of the centrum was obtained by fixation in 1% KMnO4 for 2.5-3 hr, followed by the Giemsa stain. This method is suggested for future studies on the morphology of perithecial ascomycetes.