FIGURE 2. A–F. TEM micrographs of Spelaeonaias floccida. A. Longitudinal section showing a septum (s) without intercellular connection between vegetative cells, the outer membrane (om) and the plasma membrane (pm). Note the thick and compact sheath near the cell wall, becoming diffluent externally. the thylakoids are scattered throughout the cyatoplasm forming curled bundles of 2–4 parallel arranged membranes, with phycobilisomes (pb) on their surface. B. Grazing thin section providing a top view of phycobilisomes as stellate structures, associated with thylakoidal membranes; the plasma membrane is followed by a thin layer of peptidoglycan (pl) and an outer membrane (om). C. Carboxysomes (cb) seen as polyhedral bodies. D. Peptidoglycan layer crossed by pore structures (arrow). E–F. Nucleoid regions surrounded by thylakoids and scattered through the cytoplasm; cy = cyanophycin granule. Scale bars = 500 nm (A, C–F) and 100 nm (B).