Fig. 2

Transmission electron microscopy of Zygnema circumcarinatum SAG 698-1b. a cross section through a filament illustrating the massive extracellular matrix (ECM, arrowheads) outside of the cell wall (CW), b longitudinal section with pyrenoid (P) and chloroplasts (Ch), and the cell wall (CW) surrounded by ECM (arrowheads), c detailed view of the cell wall (CW) in the attachment area of two cells, covered by a fibrillar ECM layer (arrow). Scale bars: a, b: 5 µm, c: 500 nm