“WEEDS” OF THE SEA
The sea holds many strange plants that have taken on fantastic sizes and shapes because of their underwater environment. In spite of their size, these plants are usually among the most primitive—a simple sheet of cells. Such plants are called algae and are subdivided according to their colors.
The Brown Algae
Common Rockweed (Fucus, several species)
Brown, flattened body Central midrib Stem has air bladders
The bladders are filled with air, and children like to squeeze them to hear their pop. These bladders cause the plant to float upright, thus keeping all its sides in contact with water.
Nodose Rockweed (Ascophyllum nodosum)
Thin, round stem No central midrib
When dried by the sun, this plant makes an interesting and lasting souvenir, for it turns a lustrous black.
Common Kelp (Laminaria agardhii)
Broad, flat blade Several feet in length
The kelps of the Pacific grow several hundred feet in length, making them the largest of the algae and among the very largest plants.
Fingered Kelp (Laminaria digitata)
Many blades, extending like fingers on a hand
All kelps have a rootlike structure called a “holdfast” to serve as an anchor. Often tiny sea creatures dwell in among the holdfast. Why not take a look?
Perforated Kelp (Agarum cribrosum)
Central midrib Broad blade punctured with hundreds of holes
In Asia this kelp is farmed for food called agar. An extract of the plant, agar-agar, is used in the laboratory as a culture medium for bacteria and other disease-producing organisms.
The Green Algae
Sea Lettuce (Ulva species)
A sheet of green
This is a very simple seaweed that reproduces itself by fragmentation, each fragment growing into a new plant. Two common kinds are found at Crane’s Beach:
Ulva lactuca, which is the broad green “leaf”; Ulva lanceolata, which is in thinner, more ribbon-like strips.
The Red Algae
Irish Moss (Chondrus crispus)
Flattened, branching fronds Purple in life, white when sun-bleached
Here is a very common tidal plant that has commercial value. It is called “Dulse” on the Boston markets, and a very delicious pudding is prepared from it (seamoss farine). Why not take some home and try it?
Polysiphonia (Polysiphonia, several species)
Pink or red color Branching, lace-like appearance
Sometimes called “Mermaid’s Hair,” these tiny plants are very common on the beach. There are many kinds of Polysiphonias, but a microscopic study is usually necessary to tell them apart.
Coralline Algae (Coralline, several species)
White or pink limy covering Appear jointed
These plants have the amazing ability of concentrating lime from the sea water and depositing it on their fronds, thus acquiring a stony, coral-like appearance.