A group of Eukarya which are mostly red in colour; no flagellated cells are formed, and the storage product is a type of starch known as floridean starch. Sexual reproduction tends to be complicated. Red algae may be unicellular, but most are filamentous or membranaceous. The majority occur in the sea, but some are freshwater or terrestrial. The group includes 1 class (Rhodophyceae) with many orders and more than 4000 species. The red seaweeds are more numerous than green and brown seaweeds in temperate and tropical regions, but less numerous in colder regions. Several red seaweeds yield useful products (e.g. agar, algin, and carragheen). The red algae are believed to be one of the oldest groups of eukaryotic algae.
Subjects: Plant Sciences and Forestry.