Chlorella Beijerinck: Oocystaceae. Green algae. Microscopic, one-celled, spherical, free-floating and non-settling (planktonic) algae. The green chloroplast is carried against a side of each cell, filling half or more of the volume. Cells have no flagella or whip-like "tails," but although non-motile they can float freely or aggregate into clumps or can be found as "scum" on hard surfaces. Dense blooms of suspended cells produce green turbid water, creating taste and odor problems, usually described as musty. Very large populations are produced in waters with high levels of nutrients and organic material.