Cells are heteropolar with a triangular foot pole which narrows into a thin extension. Cells are connected by the valve faces of the foot poles into chains which are often star-shaped. A. glacialis can form extensive blooms. A. glacialis is a cosmpolitan species.
of the colonial diatom, Asterionella formosa (Hassall, 1850). The linear frustules have expanded ends. The frustules of the colony are connected by gelatinous cushions at the larger of their two ends in a radial array all in more or less the same plane The yellow chloroplasts are seen here. Blooms of this diatom may impart a disagreeable fishy taste to fresh water. Collected from freshwater pond near Boise, Idaho January 2003. Phase contrast illumination.