Structural differentiation in filamentous cyanobacteria. (a)Initial stageof hormogonium formation in Oscillatoria. Notice the empty spaces wherethe hormogonium is separating from the filament. (b hormogonium of a smaller Oscillatoria speicies. Notice that the cells at both ends are rounded. Nomarski 6 Interference contrast microscopy (c)Akinete(restingspore)of Anabacna sp by phase contrastStructural differentiation in filamentous cyanobacteria.(a)Initial stageof hormogonium formation in Oscillatoria.Notice the empty spaces wherethe hormogonium is separating from the filament.(b)hormogonium of a smaller Oscillatoria speicies.Notice that the cells at both ends are rounded.Nomarski interference contrast microscopy. (c)Akinete(restingspore)of Anabacna sp.by phase contrast