Examples: Palmaria, Coralline algae
Characteristics: The red colour of these algae results from the dominance of the pigments phycoerythrin and phycocyanin; this masks the other pigments, Chlorophyll a (no Chlorophyll b), beta-carotene and a number of unique xanthophylls. The main reserves are typically floridean starch, and floridoside. and true starch is absent. The walls are made of cellulose and agars and carrageenans, both long-chained polysaccharide in widespread commercial use. There are some unicellular representatives of diverse origin; more complex thalli are built up of filaments.
A very important group of red algae is the coralline algae, which secret calcium carbonate on to the surface of their cells. Some of these corallines are articulated, with flexible erect branches; others are crustose. These corallines have been used in bone-replacement therapies.Coralline algae were used in ancient times as vermifuges.