Tolypothrix (toll-eep-o-thricks) is a filamentous blue-green alga (cyanobacterium) which expresses false branching, i.e., the cells divide in one plane only, but a heterocyst may cause cells to break free and form an apparent branch. Two false branches are shown in this image. Heterocysts are differentiated thick-walled cells that provide the site for nitrogen fixation, and three are prominent in this image. Differential interference microscopy.

data on this strain.