Spirogyra reproducing. Brightfield illuminated light micrograph of Spirogyra sp. algae conjugating. This filamentous green algae is named for the spiral arrangement of its chloroplasts (green). It's cylindrical cells connect end to end in long green filaments. Conjugation is the processes by which spirogyra reproduce. It involves the transferal of the male gamete from one filament to another, where it fuses with the female gamete to form a zygospore. Magnification: x100 when printed 10 centimetres wide.