Seaweed
"Seaweed" is a colloquial term and lacks a formal definition. A seaweed may belong to one of several groups of multicellular algae: the red algae, green algae, and brown algae. As these three groups do not have a common multicellular ancestor, the seaweed are in a polyphyletic group. In addition, some tuft-forming bluegreen algae (Cyanobacteria) are sometimes considered to be seaweed.
Monostroma
Monostroma is a genus of marine green algae (seaweed) in the family Monostromataceae. As the name suggests, algae of this genus are monostromatic (single cell layered). "Monostroma kuroshiense", an algae of this genus, is commercially cultivated in East Asia and South America for the edible product "hitoegusa-nori" or "hirohano-hitoegusa nori", popular sushi wraps. "Monostroma" oligosaccharides with degree of polymerization 6 prepared by agarase digestion from "Monostroma nitidum" polysaccharides have been shown to be an effective prophylactic agent during "in vitro" and "in vivo" tests against Japanese encephalitis viral infection. The sulfated oligosaccharides from "Monostroma" seem to be promising candidates for further development as antiviral agents. The genus "Monostroma" is the most widely cultivated genus among green seaweeds.