Observations on the selective demonstration of nucleolar material by protein staining techniques in epon thick sections.

The effect of different protein stainings on thick sections of Epon embedded salivary glands of Chironomus pallidivittatus is described. Pretreatment of sections with several metallic salts affected the affinity for aniline blue black in different structures. The uranyl and aluminium ions followed by aniline blue black resulted in a highly selective nucleolar staining which proved also efficient in Allium cepa meristematic cells and which seems useful for the preferential demonstration of nucleolar material in thick sections.