Rhodophyceae: The Red Algae

Rhodophyceae is a very large class, encompassing approximately 4,000 species. Some of these are found in northerly latitudes, but most are found further south. Color varies among the red algae and is certainly not always red. A number of red algae are used as food. Porphyra is used for food in Japan. Chondrus is used in beer manufacture and making desserts. Rhodymenia is used in making candy. While most species of red algae are small (not more than one centimeter across), a few can grow to be two feet or more in width.

No motile cells are found in the red algae, including among the gametes and spores. The pigments are chlorophyll a, possibly chlorophyll d, carotenes, and phycocyanin and phycoerythrin (two pigments also present in the bluegreen algae). The product of photosynthesis is a kind of starch found only in this group: floridian starch. Both uninucleated and multinucleated forms are known. Griflthsia has thousands of nuclei per cell.

All red algae compose the single class Rhodophyceae, which is divided into two subclasses: the Bangiophycidae and the Floridiophycidae.