Fucus, of which it is taxonomically an ally, and often produces considerable beds, though not everywhere abundant like the Fucus. In Figure 11 a group of Pelvetia is Fig. 16. A Frond of Desmarestia ligulata herbacea taken from the Wash after a Storm. shown and its habit can easily be I recognized.
Of the low-tide algae there is not only a characteristic segregation relative to depth of water, but a careful selection of habits more or less exposed to the influence of the surf and surge. Quite a characteristic group of surf-plants including such kelps as Postelsia palmaeformis and one species of Alaria display themselves where the surf is strongest and seem to require the foaming water of the breakers for their best development. Below these in more sheltered places one finds Hedophyllum, Alaria and Egregia. Below Postelsia, but exposed to strong surge, grow the Lessonias, while Pterygophora seeks the bottom of the surge and Fig. 17. Plant of the Rhodomela floccosa taken from the Wash and Photographed in a Glass-bottomed Tank. Nereocystis anchors itself in still deeper water outside the line of breakers. In this outer zone, too, Macrocystis and Dictyoneuron seem to find their best opportunities for growth, while Costaria comes somewhat nearer shore. The latter is, however, commonly brought up with the Nereocystis holdfasts, when they are detached from the bottom. Figure 13 shows the exposure of surgeplants at low tide. On the right is Lessonia littoralis. In front is Laminaria bongardiana and on the left is Phyliospadix scouleri. The Lessonia, in particular, is beautifully adapted by its massive trunk and slender leaves to maintain its foothold in the surge and with Postelsia in the surf and Nereocystis in the deeper water shows in magnificent fashion the work-