red algae, members of the division Rhodophyta (about 34,000 100 species), predominantly marine algae often found attached to other shore plants near tropical and subtropical shores. Their morphological range , though not so extensive as that of the brown algae, includes filamentous, branched, feathered, and sheetlike thalli. Thin In most species, thin protoplasmic connections provide continuity between cells. Their usual red or blue colour is the result of a masking of chlorophyll by the phycobilin pigments (phycoerythrin and phycocyanin).

The reproductive bodies of red algae are nonmotile. The female sex organ, called a carpogonium, consists of a uninucleate region that functions as the egg and a trichogyne, or projection, that acts as the sperm receptacle. Nonmotile to which male gametes become attached. The nonmotile male gametes (spermatia) are produced singly in the male sex organorgans, the spermatangiumspermatangia.

Red Some red algae are important food plants (e.g., laver, dulse) and . They may retain both their colour and gelatinous nature when cooked. Industrially, Irish moss (Chondrus) is used as a gelatin substitute in puddings, toothpaste, ice cream, and preserves. Some species of Corallina and its allies are important, along with animal corals, in forming coral reefs and islands. Agar, an amorphous a gelatin-like substance prepared primarily from Gracilaria and Gelidium species, is important as a culture medium for bacteria and fungi.