Charasome structure, with special attention to the periplasmic space, is examined using various techniques. The periplasmic space appears electron lucent in sections stained with 2% aqueous uranyl acetate and lead citrate. When sections are stained with saturated methanolic uranyl acetate a densely staining central core can be seen within the periplasmic space. The region surrounding the core does not stain. If tannic acid is added to the fixative and rinse solutions during preparation of the tissue for TEM, the entire periplasmic space becomes stained. This space appears to be filled with a fine granular material. Charasomes prepared in this way appear as negatives of those stained with uranyl acetate. The periplasmic space does not contain polysaccharides of the type havingvic-glycol groups, as indicated by lack of staining by the silver methenamine technique.