Hypnea

Hypnea is a genus of red algae, and a well known carrageenophyte (plant producing polysaccharide carrageenan).

== Taxonomy and nomenclature == Hypnea is a genus of red seaweed under class Florideophyceae, order Gigartinales, and family Cystocloniaceae. There are 99 species listed on Algaebase with 78 being accepted taxonomically. The genus was originally classified under family Hypneaceae, which was considered distinct from Cystoclonoiaceae on the basis of differences in their carposporophyte structure, and the shape of the thalli and cortical cells. Differences in carrageenan chemistry, with Hypneaceae species producing kappa-carrageenan and Cystocloniaceae producing lambda-carrageenan, was another reason for their distinction. However, these criteria were questioned and molecular analysis later showed that the two families had similar vegetative and reproductive characters. Furthermore, it was proven that lambda-carrageenan and kappa-carrageen coexist within the Gigartinales order. This led to the two families being merged into simply Cystocloniaceae.