F. serratus is a robust alga, olive-brown in colour and similar to Fucus vesiculosus and Fucus spiralis. It grows from a discoid holdfast up to 180 centimetres (6 ft) long. The fronds are flat, about 2 cm (0.8 in) wide, bifurcating, and up to 1 m (3 ft 3 in) long including a short stipe. It branches irregularly and 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. Male and female receptacles are on different plants.[2] The lamina shows cryptostomata – small cavities which produce colourless hairs.[3]
The reproductive bodies form in conceptacles sunken in receptacles towards the tips on the branches. In these conceptacles oogonia and antheridia are produced and after meiosis the oogonia and antheridia are released. Fertilisation follows and the zygote develops, settles and grows directly into the diploid sporophyte plant.
Distribution[edit]