Spirogyra is a genus of filamentous charophyte green algae, in this image we can see a process called "conjugation", a form of sexual reproduction. Two filaments of Spirogyra form conjugation tubes. The contents of one cell passes through the tube an fuses with a cell from the other filament. I'm sudent in Biological science at university of Rome Tor Vergata. photo from optical microscope with my xperia z1.