Electron microscopic observations of freeze-fracture replicas of Anabaena cells obtained by the procedures described by Bullivant and Ames (J. Cell Biol., 1966) indicate that the frozen cells are fractured in many different planes. This fracturing or cleaving along various planes allows one to gain a three dimensional relation of the cellular components as a result of such a manipulation. When replicas that are obtained by the freeze-fracture method are observed in the electron microscope, cross fractures of the cell wall and membranes that comprise the photosynthetic lamellae are apparent as demonstrated in Figures 1 & 2.A large portion of the Anabaena cell is composed of undulating layers of cytoplasm that are bounded by unit membranes that comprise the photosynthetic membranes. The adjoining layers of cytoplasm are closely apposed to each other to form the photosynthetic lamellae. Occassionally the adjacent layers of cytoplasm are separated by an interspace that may vary in widths of up to several 100 mu to form intralamellar vesicles.
