Improved staining procedures for semithin epoxy sections of plant tissues.

Improved and reliable methods are described for staining semithin sections of plant materials fixed in glutaraldehyde-osmium and embedded in epoxy resins. One-micron sections are fixed to slides, stained with a two-solution hematoxylin procedure or with a methylene blue-azure A combination, counterstained in aqueous safranin O, cleared, and mounted permanently. Basophilic tissue components are stained gray to black by the hematoxylin and blue or purple by the methylene blue-azure A combination; cell wall structures are colored by the safranin. With the procedures recommended, stains are sharp and intense, sections are flat, wrinkling and loss are held to a minimum, and unsightly precipitates do not form.