Filamentous algae can be found worldwide in fresh water and marine environments. Numerous species of filamentous algae exist, all with similar growth and appearance, and often more than one species is present in a water body at the same time. Some of the more common forms can be distinguished by their texture. Spirogyra is bright green and slimy to the touch, Cladophora has a cotton-like feel, and Pithophora has a coarse texture similar to horse hair. They typically appear as a “mat” or mass usually green in color, but may become yellow, gray to brown, long, stringy hair- like strands. Individual filaments are a series of cells joined end to end for a threadlike appearance. These filaments entwine and can form mats resembling wet wool, cotton, or slime, starting in the early spring.