Dinoflagellates, algae and sphagnum moss. Polarised light micrograph of Gymnodinium sp. dinoflagellates (oval, centre) and Spirogyra sp. filamentous green algae (bottom) amongst Sphagnum sp. moss leaves (top). Dinoflagellates are unicellular protozoans. About 90% are found in marine environments as plankton. Gymnodinium species are naked dinoflagellates, lacking protective cellulose plates. Spirogyra is named for the spiral arrangement of its chloroplasts. It's cylindrical cells connect end to end in long green filaments. Magnification: x400 when printed 10 centimetres wide.