Spirogyra is a genus of green algae that is commonly found in freshwater environments such as ponds, streams, and ditches. The filament of Spirogyra is a long, slender, multicellular structure that consists of elongated cells arranged end-to-end. Each cell has a large, central chloroplast that gives the filament its green color. The cell walls of Spirogyra are unique in that they are made of a spiral-shaped, cellulose-based structure called a spiral band. The filament is anchored to a substrate, such as a rock or a piece of debris, by a holdfast. The filament reproduces asexually by fragmentation, which occurs when the filament breaks into individual cells that can grow into new filaments.