This title, generally translated "born in the purple," either refers to the purple robes in which the imperial children were wrapped at birth, or to a chamber or part of the imperial palace, called the Porphyra (iropckpa), where the births took place.
Structurally they are either a plate of cells, as in Porphyra, or filaments, as in Bangia.
Laminaria, Padina, Cutleria, Punctaria, Iridaea, Ulva, Porphyra, are leaf-like with a rigidity varying from a fleshy lamina to the thin and pliable.
Compare, for example, the blue-green Gloeocapsa with the green Gloeocystis, the red Batrachospermum with the green Draparnaldia, the red Corallina with the green Cymopolia, the green Enteromorpha with the brown Asperococcus, the green Ulva with the red Porphyra, the red Nemalion with the brown Castagnea, and so on.
Porphyra laciniata and Rhodymenia palmata are locally used as food, the latter being known as dulse.