Gigartinales

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Gigartinales (division Rhodophyta) 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.