evident, and in Figure 10 is shown an arrangement of algae and animals upon a much creviced slate. Barnacles of two distinct types and mussels, mingled with a growth of Endocladia muricata, appear in this
Fig. 14. Corallinaceae at the Edge of a Tide-pool, on the Right Amphiroa and on the Left Corallina.
view, but the general grouping is less clearly concentric. Nevertheless the Endocladia zone is pretty well defined as a mid-tide algal society and sometimes shows sharp demarcation when favorably situated for a pure growth.
Fig. 15. A Plant of Codium Mucronatum californicum, a Characteristic Siphonacaeous alga of the Tide-pools.
Among the high-tide algae—those occupying the upper zones—Pelvetia is an interesting form. It occurs at the same levels adopted by
