The function of the mucilaginous sheath of blue-green algae is to bind colonies together and to permit movement. The mechanism of this movement is not fully understood. The mucilaginous sheath is made of strands of cellulose and often bears pigments that give colonies of blue-green algae distinct colors.
Blue-green algae are a very old group of organisms, with fossils dating back billions of years.
They have a strong resemblance to the photosynthetic structures in the cells of plants and algae. They are a type of bacteria and have no nuclei or other membrane-bound organelles. Their outer membranes are often quite folded, which gives them a large surface area. They are photosynthetic organisms, meaning they can generate usable energy from sunlight. They are not the only bacteria capable of this, but they are distinct from most others in that they can produce oxygen in the process.
Blue-green algae, which are also known as cyanobacteria, often grow together in filaments or tufts, which can reach up to a meter in length. Individual cells usually reproduce by binary fission, and their daughter cells often move away to begin a separate colony. Existing colonies can also split to form two new colonies. Their ability to move allows the groups to separate relatively rapidly.