Plant
Algae comprise several different groups of organisms which produce food by photosynthesis and thus have traditionally been included in the plant kingdom. The seaweeds range from large multicellular algae to single-celled organisms and are classified into three groups, the brown, red and green algae. There is good evidence that the brown algae evolved independently from the others, from non-photosynthetic ancestors that formed endosymbiotic relationships with red algae rather than from cyanobacteria, and they are no longer classified as plants as defined here.
Wakame
In Old Japanese, "me" stood for edible seaweeds in general as opposed to "mo" standing for algae. In kanji, such as 海藻, 軍布 and 和布 were applied to transcribe the word. Among seaweeds, wakame was likely most often eaten, therefore "me" especially meant wakame. It expanded later to other seaweeds like kajime, hirome (kombu), arame, etc. Wakame is derived from "waka" + "me" (若布, lit. young seaweed). If this "waka" is a eulogistic prefix, same as the "tama" of tamagushi, wakame likely stood for seaweeds widely in ancient ages. In Man'yōshū, in addition to 和可米 and 稚海藻 (both are read as "wakame"), "nigime" (和海藻, soft wakame) can be seen. Besides, "tamamo" (玉藻, lit. beautiful algae), which often appeared in Man'yo-shu, may be wakame depending on poems.