hfb's Favorites

A Brown Algae. Genus Fucus is vesicled and dichotomously branched. (Fucus = seaweed in Greek).

"When a seaweed branches dichotomously it produces two nearly equal branches, directly opposite each other, looking much like the letter Y. As this process is repeated, the plant assumes an overall flattened appearance. . ."
Pacific Seaweed: a Guide to Common Seaweeds of the West Coast. 2nd ed., Louis D. Druehl and Bridgette E. Clarkston, pp. 180-182.

Per SEANET (Stanford University’s Hopkins Marine Station) what was previously identified as Fucus distichus, is now called Fucus gardneri:
Fucus gardneri
Phylum Ochrophyta, Class Phaeophyceae, Order Fucales, Family Fucaceae
Thallus to 25 cm tall, flattened dichotomous branches with midrib, 15-25 mm wide; olive-brown. Reproductive conceptacles concentrated at branch tips (swollen when mature).
Common, upper mid-intertidal zone, protected outer coast.
Geogr. Range: Washington to Pt. Conception
Synonyms: previously identified as Fucus distichus
https://seanet.stanford.edu/brown#Fucus