Fixation of Microscopic Fresh-Water Green Algae by 31% OsO4in CCI4in an Unbuffered, Two-Phase Fixative System

The fixative was prepared by dissolving 0.1 gm of OsO4 in 0.2 ml of CCI4. It was applied to microscopic green algae, concentrated by centrifugation, in a volume equal to that of the residual culture medium and allowed to act for 45 min at either 20 or 4 C. Such fixation has proved of value in producing an electron micrographic picture of particular use in the study of cytoplasmic microtubules. The fixative acts by diffusion of OsO4, from the nonaqueous to the aqueous phase and thus provides a condition similar to that of vapour fixation but with a much higher concentration of OsO4