Scytonema sp. (Agardh) ex Bornet & Flahault, 1887
The trichome consists of cylindrical cells and is of uniform diameter throughout. The sheath is of firm texture and may be coloured. At some points along the trichome it may break and the ensuing two ends grow out of the sheath as separate filaments. This gives the appearance of branching. Heterocysts may develop singly or in twos or threes. They are of the same size as vegetative cells. Akinetes are rare.
Scytonema is found in subaerial habitats with the filaments interwoven into dark mats due to the mucilaginous matric absorbing dust blown off the surroundings.
Through "false branching" the filaments fragment.
Growth results in untidy stains on walls of buildings.
Bold, H. C., C. J. Alexopoulos & T. Delevoryas, 1987. Morphology of plants and fungi. Harper & Row, New York. (5th ed.). 912pp.