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.
Seaweed collecting
Anna Atkins, thought to be the first female photographer, published the first book using photographs as illustrations. This was "Photographs of British Algae: Cyanotype Impressions" and contained pictures of seaweed.