Light micrograph of the freshwater green alga Coelastrum spec. Coelastrum forms hollow, spherical or polyhedral colonies with mostly 8 to 32 cells. The colonies are immobile. The cells have a chloroplast and a pyrenoid. Culture material of the algae collection at the University of Cologne (CCAC). Microscopic contrast method : Differential interference contrast. Magnification 920x at a print width of 10 cm.