One of the largest kelps; grows upwards of 50 m long. Numerous stipes arise out of a wide holdfast made up of many irregularly whorled haptera; the stipes may be split 4 or 5 times dichotomously at the base of the plant. Plant continues to grow through it's entire life. Blades occur at regular intervals along the stipes, connecting with a pneumatocyst and flattening into a wrinkled blade, toothed along the edges. Sporophylls surround the base of the plant, just above the holdfast. The sporophylls contain reproductive spores and can be used to find the reproductivity of the plant. SAMPLING CODE NOTES: MABL = Blade; MAHO = Holdfast; MAPY = Recruit, small blades before split; MASP = Stipes split and <= to 1 m.

Frequent, grows in dense forests visible from the surface on hard substrate.

Subtidal from 6 to 30 m;Alaska to Baja California, Mexico, and South America.