Gracilariaceae

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Gracilariaceae (order Gigartinales) A family of red seaweeds in which the thallus is cylindrical, strap-like, or broadly lobed. Gracilaria is the only British genus; the thallus is dark purplish-red, cylindrical, and irregularly branched, with a discoid holdfast. It is found attached to rocks at and below low-water mark.