Fucus serratus is a seaweed of the north Atlantic Ocean, known as toothed wrack or serrated wrack.  It is olive–brown in colour and similar to F. vesiculosus and Fucus spiralis. It grows from a discoid holdfast. The fronds are flat, about 2 cm wide, bifurcating, and up to 1 m long including a short stipe. It branches irregularly dichotomously. The flattened blade has a distinct midrib and is readily distinguished from related taxa by the serrated edge of the fronds. It does not have air vesicles, such as are found in F. vesiculosus, nor is it spirally twisted like F. spiralis.
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