Many of the most beautiful plants on the seashore are red algae, as are some food plants, especially laver, dulse, and Irish Moss. Various red algae are a source of agar, a gelatinous substance with a wide variety of commercial uses. Brown algae include common seaweeds. Free-floating masses of Sargasso, or gulf, weed live in warm regions of the oceans. Kelp is eaten as a vegetable in the Orient.
Some kelp has a thick, tough stem that can be used as rope.
They may be numerous enough to color a body of water. Golden or golden brown algae include diatoms, one-celled plants with a tiny shell or exterior skeleton. When diatoms die, their shells fall to the bottom forming deposits that may build up to several meters. These shells are used as abrasive ingredients in some cleansing powders. Botanically algae are classified among the thallophytes, along with fungi, lichens, and primitive, single-celled plants and bacteria.