short chains of cylindrical or barrel-shaped cells which, after ceasing motility, enlarge to become spherical cells (Heterocysts develop in both intercalary and terminal positions when levels of combined nitrogen are low. Growth continues with cell divisions in more than one plane), so that multiseriate trichomes develop.
however, since the growing mass of cells commonly fragments into clusters or amophos aggregates of cells, generally within a mucilaginous sheath