Spirogyra is a filamentous green algae as shown in figure 1. It is known for its characteristic arrangement of chloroplasts that can be helical or spiral. It is capable of both sexual and asexual reproduction.
Sexual reproduction like in many organisms in spirogyra also takes place by conjugation that can be scalariform or lateral conjugation. In which cells of two filaments lying side by side are joined by outgrowths called conjugation tubes as shown in figure 2.
Asexual or vegetative reproduction however takes place by fragmentation as shown in figure 3. As the name suggests it is the breaking of the filament accidentally. Which results in formation of multiple cell fragments. Each fragment grows on its own to produce a new plant. This however is not the only way for fragmentation; sometimes invagination can lead to the formation of cross walls. These cross walls separate two algal cells apart hence leading to the formation of two independent fragments.