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.
Phycodrys rubens
"Phycodrys rubens" is seaweed which is perennial and can grow to 30 cm long and is strongly red in colour. It grows with flat leaf-like blades which are monostromatic, that is composed of a single flat layer of cells and can grow 3 cm wide. These blades can become 3 cm wide and show a clear mid-rib. The blades have a ruffled margin with veins growing out from the central mid-rib with paired lateral veins. The plants grow from a small disk holdfast with an axis to the blades.
The algae are somewhat similar to "Delesseria sanguinea" which is also strongly red but has a smooth, not dentate, margin. The shape of the frond is similar to the leaf of an Oak tree.