<p><strong>Fig. 2.21.</strong> (<strong>A</strong>) Toothed wrack seaweed, <em>Fucus serratus</em>, blades with thickened midribs</p>

Fig. 2.21. (A) Toothed wrack seaweed, Fucus serratus, blades with thickened midribs

Image courtesy of Stemonitis, Wikimedia Commons