An order of red seaweeds, in which the thallus is crustose (Cruoriaceae) or cylindrical, compressed or membranaceous, and branched or unbranched. There are many families and genera. Gigartina stellata is a common species which forms dense, dark-red tufts on rocks in the intertidal zone, often occurring in dense colonies. This species has been used commercially as a source of agar.
Subjects: Plant Sciences and Forestry.