noun
common hornwort; Ceratophyllum demersum
A submerged aquatic plant often used in aquariums and found in ponds and slow streams.
水槽にマツモを入れると、水がきれいになる。
If you put hornwort in the aquarium, the water becomes clean.
noun
Analipus japonicus; a brown alga
A species of brown alga found along Japanese coasts; less commonly encountered than the hornwort sense.
この海岸では、マツモという褐藻が採れる。
On this coast, a brown alga called matsumo can be collected.
The name literally means 'pine seaweed', from 松 (pine) and 藻 (seaweed/algae), referring to the plant's resemblance to pine needles.