Spirogyra sp. (Gr. speira, coil & Gr. gyros, twisted) zygnematalean green alga filament, focused to the middle of the cell, showing the nucleus. Spirogyra forms filaments composed of cells having spiral, ribbon-shaped chloroplasts. Culture material of the Culture Collection of Algae at the University of Cologne. Microscopic contrast technique : Differential interference contrast. Magnification 370x when printed 10 centimetres wide.