At the end of the bloom, older filaments developed terminal
segments of elongated colorless cells. The heterocysts and akinetes were also
smaller than those reported by Forti. The spherical heterocysts, 3-5 um in diameter,
were usually located in the middle of the trichome, but also occasionally at
the tip. Akinetes were 5-10 um in diameter and 7-15 um long, located in the
middle of the trichome, very rarely adjacent to the heterocyst, and sometimes also
at a terminal position. The distance between heterocysts and akinetes varied from
20 to 60 um, rarely 90-120 um