Answer: mucilaginous sheath
Explanation:
These algae are known as "blue algae" because of their pigmentation or "cyanobacteria" because they are prokaryotes. Microbiologists classify cyanobacteria in the realm of Eubacteria. They are the only prokaryote algae. The cellular organization is prokaryotic, without nuclei or organelles. Respiration takes place at the level of plasmalemma and thylakoids. In the center (nucleoplasm), cells contain their genome and circular plasmids. Cyanobacteria often also have a mucilaginous sheath common to many trichomes.
These organisms contain several carotenoid pigments, particularly myxoxanthophyll, which does not occur in any other algae group. Some cyanobacteria are strictly phototrophic, others are optional: they are phototrophic when in the presence of light, but may grow in obscurity using an organic carbon source. Others can use a source of organic carbon as well as inorganic carbon, but only in the presence of light.
