Chlorella. Scanning electron micrograph (SEM). Chlorella is a genus of single celled green algae lacking a flagellum. It is considered a promising alga for industrial applications because of its ability to accumulate high levels of proteins and other essential nutrients and is actually in use as food additive for human nutrition. Under certain conditions chlorella can also produce high levels of polyunsaturated fats. Magnification: x10000, when printed 10 centimetres wide. Specimen courtesy of Mike Allen, Plymouth Marine Laboratory.