Family Description:
Blades are undivided; they have a central midrib or thickening, and are borne on a simple or dichotomously branched stipe. Sori occur on sporophylls, which develop in opposite rows along the stipe near the intercalary meristem at the junction of stipe and blade. As currently constituted, the family contains only three genera: Alaria, Pterygophora, and Lessoniopsis. The last two genera are monotypic; that is, they consist of only a single species each.

Species description:
Thallus has a stiff, woody stipe to 1.5 m (60 in.) long and blade-like sporophylls attached along the flattened distal margins of the stipe, which usually terminates in a small, smooth blade with a faint midrib. This tough kelp can reach 2.3 m (7.5 ft) tall.

Source:  North Pacific Seaweeds