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.
Thallophytes are plants devoid of true roots, stems, leaves, or flowers.
Certain algae have some qualities of plants and some qualities of animals. They are sometimes called protozoan animals, or they may be classified as protists, somewhere between the plant and animal kingdoms. The Learning Company, Inc.